poky: subtree update:c67f57c09e..c6bc20857c
Adrian Freihofer (2):
oe-publish-sdk: fix layers init via ssh
oe-publish-sdk: add --keep-orig option
Alexander Kanavin (68):
meta-selftest: correct the virgl test for 5.8 kernels
bison: upgrade 3.6.4 -> 3.7.1
util-linux: upgrade 2.35.2 -> 2.36
python3-numpy: upgrade 1.19.0 -> 1.19.1
python3-setuptools: upgrade 49.3.1 -> 49.6.0
rsync: upgrade 3.2.2 -> 3.2.3
util-linux: merge .inc into .bb
acpica: upgrade 20200528 -> 20200717
asciidoc: upgrade 9.0.1 -> 9.0.2
cryptodev: upgrade 1.10 -> 1.11
diffoscope: upgrade 153 -> 156
epiphany: upgrade 3.36.3 -> 3.36.4
font-alias: upgrade 1.0.3 -> 1.0.4
gtk+3: upgrade 3.24.21 -> 3.24.22
libcheck: upgrade 0.15.0 -> 0.15.2
libinput: upgrade 1.16.0 -> 1.16.1
libpipeline: upgrade 1.5.2 -> 1.5.3
libx11: upgrade 1.6.9 -> 1.6.11
linux-firmware: upgrade 20200619 -> 20200721
man-pages: upgrade 5.07 -> 5.08
mc: upgrade 4.8.24 -> 4.8.25
mesa: upgrade 20.1.4 -> 20.1.5
piglit: upgrade to latest revision
re2c: upgrade 2.0 -> 2.0.2
sysstat: upgrade 12.2.2 -> 12.4.0
vala: upgrade 0.48.7 -> 0.48.9
bootchart2: update 0.14.8 -> 0.14.9
harfbuzz: convert to meson, enable gobject introspection
pango: update 1.44.7 -> 1.46.0
boost: update 1.73.0 -> 1.74.0
xev: update 1.2.3 -> 1.2.4
wpebackend-fdo: update 1.6.1 -> 1.7.1
gpgme: update 1.13.1 -> 1.14.0
libpsl: update 0.21.0 -> 0.21.1.
gettext: update 0.20.2 -> 0.21
cmake: update 3.17.3 -> 3.18.1
linux-firmware: update 20200721 -> 20200817
meson: update 0.55.0 -> 0.55.1
systemd-boot: bump version to 246.2
json-glib: inherit upstream-version-is-even
packagegroup-core-device-devel: remove
oeqa/x32lib: rework to use readelf from the host
oeqa/multilib: rework to use readelf from the host
oeqa/multilib: un-skip the connman test
poky.conf: do not install packagegroup-core-device-devel into qemu images
glib-2.0: update 2.64.4 -> 2.64.5
cmake: upgrade 3.18.1 -> 3.18.2
libxcrypt: upgrade 4.4.16 -> 4.4.17
debianutils: upgrade 4.11 -> 4.11.1
enchant2: upgrade 2.2.8 -> 2.2.9
harfbuzz: upgrade 2.7.1 -> 2.7.2
libmpc: upgrade 1.1.0 -> 1.2.0
librepo: upgrade 1.12.0 -> 1.12.1
libuv: upgrade 1.38.1 -> 1.39.0
msmtp: upgrade 1.8.11 -> 1.8.12
ninja: upgrade 1.10.0 -> 1.10.1
p11-kit: upgrade 0.23.20 -> 0.23.21
pango: upgrade 1.46.0 -> 1.46.1
re2c: upgrade 2.0.2 -> 2.0.3
resolvconf: upgrade 1.82 -> 1.83
stress-ng: upgrade 0.11.18 -> 0.11.19
gnu-config: update to latest revision
nasm: update 2.15.03 -> 2.15.05
libva-utils: fix upstream version check
gnupg: update 2.2.21 -> 2.2.22
libx11: update 1.6.11 -> 1.6.12
mesa: update 20.1.5 -> 20.1.6
xserver-xorg: update 1.20.8 -> 1.20.9
Andrey Zhizhikin (1):
insane: check for missing update-alternatives inherit
Anibal Limon (1):
recipes-kernel: linux-firmware add qcom-venus-{5.2,5.4} packages
Aníbal Limón (1):
recipes-graphics/xorg-xserver: Add patch to fix segfault when probe
Armin Kuster (2):
bind: update to 9.11.22 ESV
core-image-sato: qemumips use 512 mem
Bruce Ashfield (30):
linux-yocto/5.4: update to v5.4.59
linux-yocto/5.8: update to v5.8.2
yocto-bsp: update to v5.4.56
yocto-bsp: update to v5.4.58
qemu: bump default reference kernel to v5.8
linux-yocto/5.8: fix perf and virtio_scsi warnings
linux-yocto-rt/5.8: fix lttng-modules build
linux-yocto/5.8: selftests/bpf: Prevent runqslower from racing on building bpftool
linux-yocto/5.8: disable CONFIG_NFS_DISABLE_UDP_SUPPORT
poky: set preferred version for linux-yocto to be v5.8
poky-tiny: set preferred version to 5.8
poky: add preferred version for linux-yocto-rt
linux-yocto/5.8: update to v5.8.3
linux-yocto/5.4: update to v5.4.60
kernel: config cleanups for 5.8+
linux-yocto/5.4: update to v5.4.61
linux-yocto/5.8: update to v5.8.4
linux-yocto/5.8: disable IKHEADERS in default builds
kernel-yocto: allow promotion of configuration warnings to errors
kernel-yocto: checksum all modifications to available kernel fragments directories
lttng-modules/devupstream: bump to latest 2.12 commits
linux-yocto-dev: bump to v5.9+
linux-yocto/5.8: update to v5.8.5
kernel-devsrc: account for HOSTCC and HOSTCXX
linux-yocto/config: netfilter: Enable nat for ipv4 and ipv6
linux-yocto/5.8: update to v5.8.8
linux-yocto/5.4: update to v5.4.64
linux-yocto/config: configuration warning cleanup
linux-yocto/5.8: update to v5.8.9
linux-yocto/5.4: update to v5.4.65
Changhyeok Bae (2):
iw: upgrade 5.4 -> 5.8
iputils: upgrade s20190709 -> s20200821
Chris Laplante (12):
bitbake: compat.py: remove file since it no longer actually implements anything
bitbake: COW: formatting
bitbake: COW: migrate test suite into tests/cow
cve-update-db-native: add progress handler
cve-check/cve-update-db-native: use lockfile to fix usage under multiconfig
cve-update-db-native: use context manager for cve_f
cve-check: avoid FileNotFoundError if no do_cve_check task has run
bitbake: utils: process_profilelog: use context manager
bitbake: utils: fix UnboundLocalError when _print_exception raises
cve-update-db-native: be less magical about checking whether the cve-check class is enabled
cve-update-db-native: move -journal checking into do_fetch
cve-update-db-native: remove unused variable
Christophe GUIBOUT (1):
initramfs-framework: support kernel cmdline with double quotes
Denys Dmytriyenko (2):
weston: upgrade 8.0.0 -> 9.0.0
cryptodev: bump 1 commit past 1.11 to fix 5.9-rc1+
Diego Sueiro (2):
license_image.bbclass: Create symlink to the image license manifest dir
license_image.bbclass: Fix symlink to the image license manifest dir creation
Douglas Royds (1):
tcmode-default: Drop gcc-cross-initial, gcc-crosssdk-initial references
Frazer Clews (1):
bitbake: lib: fix most undefined code picked up by pylint
Geoff Parker (1):
systemd-serialgetty: Replace sed quoting using ' with " to allow var expansion
Jacob Kroon (1):
gcc10: Don't default back to -fcommon
Jean-Francois Dagenais (1):
bitbake: siggen: clean_basepath: remove recipe full path when virtual:xyz present
Jens Rehsack (1):
lttng-modules: backport patches from 2.12.x to fix 5.4.64+ and 5.8.9+ builds
Joe Slater (1):
pseudo: fix renaming to self
Jon Mason (4):
cortex-m0plus.inc: change file permissions
tune-cortexa55.inc: clean-up ARMv8.2a uses
tune-cortexa57-cortexa53.inc: add CRC and set march
tune-cortexa*: Cleanups
Joshua Watt (8):
wic: Add 512 Byte alignment to --offset
oeqa: runtime_tests: Extra GPG debugging
oeqa: sdk: Capture stderr output
oeqa: reproducible: Fix test not producing diffs
diffoscope: upgrade 156 -> 158
bitbake: bitbake: Add parsing torture test
bitbake: cooker: Block SIGINT in worker processes
sphinx: dev-manual: Clarify that virtual providers do not apply to runtime dependencies
Kai Kang (1):
dhcpcd: 9.1.4 -> 9.2.0
Kevin Hao (1):
meta-yocto-bsp: Bump to the v5.8 kernel
Khairul Rohaizzat Jamaluddin (1):
wic/bootimg-efi: IMAGE_EFI_BOOT_FILES variable added to separate bootimg-efi and bootimg-partition
Khem Raj (24):
gcc-cross-canadian: Install gcc/g++ wrappers for musl
uninative: Upgrade to 2.9
packagegroup-core-tools-profile: Disable lttng-modules for riscv64
lttng-modules: Disable on riscv64
kexec-tools: Fix build with -fno-common on ppc
lttng-tools: Do not build for riscv64
util-linux: Allow update alternatives for additional apps
lttng-tools: lttng-ust works on riscv64
json-glib: Backport a build fix with clang
rpcbind: Use update-alternatives for rpcinfo
go: Upgrade to 1.15 major release
weston-init: Redefine weston service and add socket activation option
musl: Upgrade to latest master
libucontext: Recognise riscv32 architecture
linuxloader.bbclass: Define riscv32 ldso for musl
populate_sdk_ext: Do not assume local.conf will always exist
weston: plane_add_prop() calls break musl atomic modesetting
weston-init: Enable RDP screen share
weston-init: Do not use fbdev backend
weston-init: Select drm/fbdev backends for qemu machines
oeqa/weston: Fix tests to run with systemd
core-image-weston: Bump qemu memory to 512M
go: Update to 1.15.2 minor release
bind: Inherit update-alternatives
Mark Hatle (6):
package_tar.bbclass: Sync to the other package_* classes
kernel.bbclass: Remove do_install[prefunc] no longer needed
buildhistory.bbclass: Rework to use read_subpackage_metadata
kernel.bbclass: Move away from calling package_get_auto_pr
package.bbclass: hash equivalency and pr service
bitbake: process.py: Handle SystemExit exception to eliminate backtrace
Mark Morton (1):
sphinx: test-manual code block, link, and format update
Martin Jansa (7):
devtool: expand SRC_URI when guessing recipe update mode
image-artifact-names: introduce new bbclass and move some variables into it
kernel.bbclass: use bash variables like imageType, base_name without {}
kernel.bbclass: eliminate (initramfs_)symlink_name variables
kernel.bbclass: use camelCase notation for bash variables in do_deploy
*-initramfs: don't use .rootfs IMAGE_NAME_SUFFIX
bitbake.conf: use ${TCMODE}-${TCLIBC} directory for CACHE
Matt Madison (1):
image.bbclass: fix REPRODUCIBLE_TIMESTAMP_ROOTFS reference
Michael Gloff (2):
sysvinit rc: Use PSPLASH_FIFO_DIR for progress fifo
sysvinit: Remove ${B} assignment
Michael Tretter (1):
devtool: deploy-target: Fix size calculation for hard links
Ming Liu (2):
systemd: split systemd specific udev rules into its own package
libubootenv: inherit uboot-config
Mingli Yu (3):
qemu: always define unknown_lock_type
qemu: override DEBUG_BUILD
bison: remove the parallel build patch
Naveen Saini (1):
lib/oe/recipeutils.py: add support for BBFILES_DYNAMIC
Nicolas Dechesne (73):
linux-libc-headers: kernel headers are installed in STAGING_KERNEL_BUILDDIR
bitbake: sphinx: add initial build infrastructure
bitbake: sphinx: initial sphinx support
bitbake: sphinx: bitbake-user-manual: use builtin sphinx glossary
bitbake: sphinx: switch to readthedocs theme
bitbake: sphinx: override theme CSS
bitbake: sphinx: fixup for links
bitbake: sphinx: fix links inside notes
bitbake: sphinx: fixes all remaining warnings
bitbake: sphinx: Makefile.sphinx: add clean and publish targets
bitbake: sphinx: tweak html output a bit
bitbake: sphinx: add SPDX headers
bitbake: sphinx: index: move the boilerplate at the end of the page
bitbake: sphinx: conf: enable extlinks extension
bitbake: sphinx: add releases page
bitbake: sphinx: bitbake-user-manual: insert additional blank line after title
bitbake: sphinx: last manual round of fixes/improvements
bitbake: sphinx: update style for important, caution and warnings
bitbake: sphinx: remove leading '/'
bitbake: sphinx: theme_override: properly set font for verbatim text
bitbake: bitbake-user-manual: fix bad links
sphinx: add initial build infrastructure
sphinx: initial sphinx support
sphinx: ref-variables: use builtin sphinx glossary
sphinx: overview-manual: add figures
sphinx: switch to readthedocs theme
sphinx: Add SPDX license headers
sphinx: add CSS theme override
sphinx: bsp-guide: add figures
sphinx: add Yocto project logo
sphinx: conf: update copyright
sphinx: conf: add substitutions/global variables
sphinx: add boilerplate file
sphinx: add boilerplate to manuals
sphinx: ref-manual: add revision history table
sphinx: add a general index
sphinx: conf.py: enable sphinx.ext.autosectionlabel
sphinx: ref-manual: use builtin glossary for the Terms section
sphinx: fix internal links
sphinx: ref-manual: fix typo
sphinx: fix custom term links
sphinx: manual updates for some links
sphinx: dev-manual add figures
sphinx: kernel-dev: add figures
sphinx: profile-manual: add figures
sphinx: fix up bold text for informalexample container
sphinx: ref-manual: add figures
sphinx: sdk-manual: add figures
sphinx: test-manual: add figures
sphinx: toaster-manual: add figures
sphinx: add links for Yocto project website
sphinx: fix links when the link text should be displayed
sphinx: add links to terms in the BitBake glossary
sphinx: add links to section in the Bitbake manual
sphinx: setup extlink for docs.yoctoproject.org
sphinx: enable intersphinx extension
sphinx: insert blank below between title and toc
sphinx: fix up terms related to kernel-fitimage
sphinx: conf: a few rendering tweaks
sphinx: makefile: add publish target
sphinx: conf: include CSS/JS files, the proper way
sphinx: convert 'what I wish I'd known'
sphinx: convert 'transitioning to a custom environment'
sphinx: ref-manual: fix heading for oe-init-build-env
sphinx: brief-yoctoprojectqs: fix up all remaining rendering issues
sphinx: Makefile.sphinx improvements
sphinx: convert bsp-guide
sphinx: remove leading '/'
sphinx: update style for important, caution and warnings
sphinx: profile-manual: convert profile-manual
sphinx: theme_override: properly set font for verbatim text
sphinx: theme_override: add tying-it-together admonition
sphinx: conf: exclude adt-manual/*.rst
Oleksandr Kravchuk (1):
ell: update to 0.33
Ovidiu Panait (1):
libxml2: Fix CVE-2020-24977
Peter A. Bigot (2):
bluez5: fix builds that require ell support
timezone: include leap second data in tzdata-core
Peter Bergin (1):
systemd: avoid failing if no udev rules provided
Pierre-Jean Texier (2):
libubootenv: upgrade 0.3 -> 0.3.1
diffoscope: upgrade 158 -> 160
Quentin Schulz (16):
sphinx: brief-yoctoprojectqs: remove redundant welcome
sphinx: brief-yoctoprojectqs: fix ambiguous note for cyclone5 example
sphinx: brief-yoctoprojectqs: add missing boilerplate
sphinx: overview-manual: add link to AUH how-to section
sphinx: overview-manual: fix bitbake basic explanation
sphinx: brief-yoctoprojectqs: add note on branch consistency between layers
sphinx: what-i-wish-id-known: update "don't be fooled by doc search results"
sphinx: overview-manual: remove highlight in bold section
sphinx: replace special quotes with single and double quotes
sphinx: fix incorrect indentations
sphinx: brief-yoctoprojectqs: put other distros note after Ubuntu-specific packages
sphinx: fix a few typos or missing/too many words
sphinx: "highlight" some variables, tasks or files
sphinx: fix or add missing links and remove mention of Eclipse workflow
ref-manual: examples: hello-autotools: upgrade to 2.10
ref-manual: examples: libxpm: add relative path to .inc
Rahul Kumar (1):
systemd-serialgetty: Fix sed expression quoting
Rasmus Villemoes (1):
kernel.bbclass: run do_symlink_kernsrc before do_patch
Richard Purdie (74):
nativesdk-sdk-provides-dummy: Add /bin/sh
bitbake: fetch2/wget: Remove buffering parameter
bitbake: cooker: Ensure parse_quit thread is closed down
bitbake: cooker: Explictly shut down the sync thread
bitbake: fetch2: Drop cups.org from wget status checks
bitbake: build/msg: Cleanup verbose option handling
bitbake: cooker/cookerdata/main: Improve loglevel handling
bitbake: cookerdata: Ensure UI options are updated to the server
bitbake: cooker/cookerdata: Ensure UI event log is updated from commandline
bitbake: cooker: Defer configuration init to after UI connection
bitbake: server/process: Move the socket code to server process only
bitbake: main/server/process: Drop configuration object passing
bitbake: cooker: Ensure BB_ORIGENV is updated by changes to configuration.env
bitbake: server/process: Log extra threads at exit
bitbake: server/process: Add bitbake-server and exec() a new server process
bitbake: runqueue: Don't use sys.argv
bitbake: cooker: Ensure cooker's enviroment is updated on updateConfig
connman-gnome/matchbox-desktop: Remove file:// globbing
selftest/recipetool: Drop globbing SRC_URI test, no longer supported
local.conf.sample: Document memory resident bitbake
bitbake: fetch2: Drop globbing supprt in file:// SRC_URIs
bitbake: server/process: Use sys.executable for bitbake-server
bitbake: process: Avoid bb.utils.timeout
bitbake: utils: Drop broken timeout function
bitbake: server/process: Fix typo in code causing tracebacks
oeqa/selftest: Apply patch to fix cpio build with -fno-common
runqemu: Show an error for conflicting graphics options
lttng: Move platform logic to dedicated inc file
patchelf: upgrade 0.11 -> 0.12
build-appliance/packagegroup-core-base-utils: Replace dhcp-client/dhcp-server with dhcpcd/kea
selftest/prservice: Improve test failure message
iputils: Adapt ${PN}-tftpd package dependency to PACKAGECONFIG
bitbake: process/knotty: Improve early exception handling
bitbake: cooker/cookerdata: Use BBHandledException, not sys.exit()
bitbake: cookerdata: Fix exception raise statements
bitbake: process: Avoid printing binary strings for leftover processes
bitbake: server/process: Ensure logging is flushed
bitbake: server/process: Don't show tracebacks if the lockfile is removed
bitbake: cooker: Ensure parser replacement calls parser final_cleanup
bitbake: cooker: Assign a name to the sync thread to aid debugging
bitbake: server/process: Ensure we don't keep looping if some other server is started
bitbake: server/process: Prefix the log data with pid/time information
bitbake: server/process: Note when commands complete in logs
bitbake: cooker: Ensure parser is cleaned up
runqemu: Add a hook to allow it to renice
bitbake: cooker: Avoid parser deadlocks
bitbake: cooker: Ensure parser worker signal handlers are default
selftest/signing: Ensure build path relocation is safe
oeqa/concurrencytest: Improve builddir path manipulations
bitbake: cooker/command: Fix disconnection handling
bitbake: tinfoil: Ensure sockets don't leak even when exceptions occur
bitbake: tests/fetch: Move away from problematic freedesktop.org urls
bitbake: sphinx: Enhance the sphinx experience/nagivation with:
bitbake: sphinx: theme_override: Use bold for emphasis text
Revert "qemu: always define unknown_lock_type"
Revert "core-image-sato: qemumips use 512 mem"
sphinx: Organize top level docs
sphinx: releases.rst: Add index/links to docs for previous releases
sphinx: boilerplate.rst: Drop versions notes as we have better navigation now
sphinx: boilerplate.rst: Sphinx puts the copyright elsewhere
sphinx: history: Move revision history to its own section
sphinx: manuals: Move boilerplate after toctree
sphinx: Add support for multiple docs version
sphinx: index.rst: Fix links
sphinx: ref-system-requirements: Improve formatting of the notes sections, merging them
sphinx: ref-manual links fixes and many other cleanups to import
sphinx: dev-manual: Various URL, code block and other fixes to imported data
sphinx: sdk-manual: Various URL, code block and other fixes to imported data
sphinx: kernel-dev: Various URL, code block and other fixes to imported data
sphinx: theme_override: Use bold for emphasis text
sphinx: ref-tasks: Add populate_sdk_ext task definition
sphinx: ref-manual/migration: Split each release into its own file
sphinx: overview-manual: Various URL, code block and other fixes to imported data
build-appliance-image: Update to master head revision
Robert Yang (3):
bitbake: cooker.py: Save prioritized BBFILES to BBFILES_PRIORITIZED
bitbake: utils.py: get_file_layer(): Exit the loop when file is matched
bitbake: utils.py: get_file_layer(): Improve performance
Ross Burton (25):
package.bbclass: explode the RPROVIDES so we don't think the versions are provides
elfutils: silence a new QA warning
insane: improve gnu-hash-style warning
gdk-pixbuf: add tests PACKAGECONFIG
debianutils: change SRC_URI to use snapshot.debian.org
insane: only load real files as ELF
autoconf: consolidate SRC_URI
autoconf: consolidate DEPENDS
kea: no need to depend on kea-native
kea: don't use PACKAGECONFIG inappropriately
kea: bump to 1.7.10
help2man: rewrite recipe
local.conf.sample.extended: remove help2man reference
curl: add vendors to CVE_PRODUCT to exclude false positives
harfbuzz: update patch status
harfbuzz: fix a build race around hb-version.h
cmake: whitelist CVE-2016-10642
ncurses: remove config.cache
qemu: fix CVE-2020-14364
cve-update-db-native: remove unused import
cve-update-db-native: add more logging when fetching
cve-update-db-native: use fetch task
alsa-plugins: improve .la removal
sato-screenshot: improve .la removal
buildhistory-diff: use BUILDDIR to know where buildhistory is
Saul Wold (1):
gnupg: uprev 2.2.22 -> 2.2.23
Stacy Gaikovaia (2):
bison: uprev from 3.7.1 to 3.7.2
valgrind: fix memcheck vgtests remove fullpath-after flags
Steve Sakoman (1):
xinput-calibrator: change SRC_URI to branch with libinput support
Sumit Garg (1):
insane: fix gnu-hash-style check
TeohJayShen (1):
oeqa/runtime: add test for matchbox-terminal
Tim Orling (1):
sphinx: toaster-manual: fix vars, links, code blocks
Vijai Kumar K (2):
image_types_wic: Add ASSUME_PROVIDED to WICVARS
wic: misc: Add /bin to the list of searchpaths
Yanfei Xu (1):
kernel-yocto: only replace leading -I in include paths
Yi Zhao (1):
glib-networking: add ptest
Zhixiong Chi (1):
gnutls: CVE-2020-24659
akuster (8):
log4cplus: move meta-oe pkg to core
kea: Move from meta-networking
maintainers.inc: Add me as kea & log4plus maintainer.
dhcpcd: Move from meta-network as OE-Core needs a client
maintainers.inc: Add me as dhcpcd maintainer
dhcp: remove from core
bind: Add 9.16.x
bind: 9.11 remove
hongxu (1):
sysstat: fix installed-vs-shipped QA Issue in systemd
zangrc (4):
libcap:upgrade 2.42 -> 2.43
libcap-ng:upgrade 0.7.10 -> 0.7.11
libgpg-error:upgrade 1.38 -> 1.39
at-spi2-core:upgrade 2.36.0 -> 2.36.1
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I5542f5eea751a2641342e945725fd687cd74bebe
diff --git a/poky/documentation/overview-manual/history.rst b/poky/documentation/overview-manual/history.rst
new file mode 100644
index 0000000..0273d28
--- /dev/null
+++ b/poky/documentation/overview-manual/history.rst
@@ -0,0 +1,28 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+***********************
+Manual Revision History
+***********************
+
+.. list-table::
+ :widths: 10 15 40
+ :header-rows: 1
+
+ * - Revision
+ - Date
+ - Note
+ * - 2.5
+ - May 2018
+ - The initial document released with the Yocto Project 2.5 Release
+ * - 2.6
+ - November 2018
+ - Released with the Yocto Project 2.6 Release.
+ * - 2.7
+ - May 2019
+ - Released with the Yocto Project 2.7 Release.
+ * - 3.0
+ - October 2019
+ - Released with the Yocto Project 3.0 Release.
+ * - 3.1
+ - April 2020
+ - Released with the Yocto Project 3.1 Release.
diff --git a/poky/documentation/overview-manual/overview-manual-concepts.rst b/poky/documentation/overview-manual/overview-manual-concepts.rst
new file mode 100644
index 0000000..3d8dc7a
--- /dev/null
+++ b/poky/documentation/overview-manual/overview-manual-concepts.rst
@@ -0,0 +1,2185 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+**********************
+Yocto Project Concepts
+**********************
+
+This chapter provides explanations for Yocto Project concepts that go
+beyond the surface of "how-to" information and reference (or look-up)
+material. Concepts such as components, the :term:`OpenEmbedded Build System`
+workflow,
+cross-development toolchains, shared state cache, and so forth are
+explained.
+
+Yocto Project Components
+========================
+
+The :term:`BitBake` task executor
+together with various types of configuration files form the
+:term:`OpenEmbedded-Core (OE-Core)`. This section
+overviews these components by describing their use and how they
+interact.
+
+BitBake handles the parsing and execution of the data files. The data
+itself is of various types:
+
+- *Recipes:* Provides details about particular pieces of software.
+
+- *Class Data:* Abstracts common build information (e.g. how to build a
+ Linux kernel).
+
+- *Configuration Data:* Defines machine-specific settings, policy
+ decisions, and so forth. Configuration data acts as the glue to bind
+ everything together.
+
+BitBake knows how to combine multiple data sources together and refers
+to each data source as a layer. For information on layers, see the
+":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`"
+section of the Yocto Project Development Tasks Manual.
+
+Following are some brief details on these core components. For
+additional information on how these components interact during a build,
+see the
+":ref:`overview-manual/overview-manual-concepts:openembedded build system concepts`"
+section.
+
+.. _usingpoky-components-bitbake:
+
+BitBake
+-------
+
+BitBake is the tool at the heart of the :term:`OpenEmbedded Build System`
+and is responsible
+for parsing the :term:`Metadata`, generating
+a list of tasks from it, and then executing those tasks.
+
+This section briefly introduces BitBake. If you want more information on
+BitBake, see the :doc:`BitBake User Manual <bitbake:index>`.
+
+To see a list of the options BitBake supports, use either of the
+following commands:
+::
+
+ $ bitbake -h
+ $ bitbake --help
+
+The most common usage for BitBake is ``bitbake recipename``, where
+``recipename`` is the name of the recipe you want to build (referred
+to as the "target"). The target often equates to the first part of a
+recipe's filename (e.g. "foo" for a recipe named ``foo_1.3.0-r0.bb``).
+So, to process the ``matchbox-desktop_1.2.3.bb`` recipe file, you might
+type the following:
+::
+
+ $ bitbake matchbox-desktop
+
+Several different
+versions of ``matchbox-desktop`` might exist. BitBake chooses the one
+selected by the distribution configuration. You can get more details
+about how BitBake chooses between different target versions and
+providers in the
+":ref:`Preferences <bitbake:bb-bitbake-preferences>`" section
+of the BitBake User Manual.
+
+BitBake also tries to execute any dependent tasks first. So for example,
+before building ``matchbox-desktop``, BitBake would build a cross
+compiler and ``glibc`` if they had not already been built.
+
+A useful BitBake option to consider is the ``-k`` or ``--continue``
+option. This option instructs BitBake to try and continue processing the
+job as long as possible even after encountering an error. When an error
+occurs, the target that failed and those that depend on it cannot be
+remade. However, when you use this option other dependencies can still
+be processed.
+
+.. _overview-components-recipes:
+
+Recipes
+-------
+
+Files that have the ``.bb`` suffix are "recipes" files. In general, a
+recipe contains information about a single piece of software. This
+information includes the location from which to download the unaltered
+source, any source patches to be applied to that source (if needed),
+which special configuration options to apply, how to compile the source
+files, and how to package the compiled output.
+
+The term "package" is sometimes used to refer to recipes. However, since
+the word "package" is used for the packaged output from the OpenEmbedded
+build system (i.e. ``.ipk`` or ``.deb`` files), this document avoids
+using the term "package" when referring to recipes.
+
+.. _overview-components-classes:
+
+Classes
+-------
+
+Class files (``.bbclass``) contain information that is useful to share
+between recipes files. An example is the
+:ref:`autotools <ref-classes-autotools>` class,
+which contains common settings for any application that Autotools uses.
+The ":ref:`ref-manual/ref-classes:Classes`" chapter in the
+Yocto Project Reference Manual provides details about classes and how to
+use them.
+
+.. _overview-components-configurations:
+
+Configurations
+--------------
+
+The configuration files (``.conf``) define various configuration
+variables that govern the OpenEmbedded build process. These files fall
+into several areas that define machine configuration options,
+distribution configuration options, compiler tuning options, general
+common configuration options, and user configuration options in
+``conf/local.conf``, which is found in the :term:`Build Directory`.
+
+
+.. _overview-layers:
+
+Layers
+======
+
+Layers are repositories that contain related metadata (i.e. sets of
+instructions) that tell the OpenEmbedded build system how to build a
+target. Yocto Project's `layer model <#the-yocto-project-layer-model>`__
+facilitates collaboration, sharing, customization, and reuse within the
+Yocto Project development environment. Layers logically separate
+information for your project. For example, you can use a layer to hold
+all the configurations for a particular piece of hardware. Isolating
+hardware-specific configurations allows you to share other metadata by
+using a different layer where that metadata might be common across
+several pieces of hardware.
+
+Many layers exist that work in the Yocto Project development
+environment. The `Yocto Project Curated Layer
+Index <https://caffelli-staging.yoctoproject.org/software-overview/layers/>`__
+and `OpenEmbedded Layer
+Index <http://layers.openembedded.org/layerindex/branch/master/layers/>`__
+both contain layers from which you can use or leverage.
+
+By convention, layers in the Yocto Project follow a specific form.
+Conforming to a known structure allows BitBake to make assumptions
+during builds on where to find types of metadata. You can find
+procedures and learn about tools (i.e. ``bitbake-layers``) for creating
+layers suitable for the Yocto Project in the
+":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`"
+section of the Yocto Project Development Tasks Manual.
+
+.. _openembedded-build-system-build-concepts:
+
+OpenEmbedded Build System Concepts
+==================================
+
+This section takes a more detailed look inside the build process used by
+the :term:`OpenEmbedded Build System`,
+which is the build
+system specific to the Yocto Project. At the heart of the build system
+is BitBake, the task executor.
+
+The following diagram represents the high-level workflow of a build. The
+remainder of this section expands on the fundamental input, output,
+process, and metadata logical blocks that make up the workflow.
+
+.. image:: figures/YP-flow-diagram.png
+ :align: center
+
+In general, the build's workflow consists of several functional areas:
+
+- *User Configuration:* metadata you can use to control the build
+ process.
+
+- *Metadata Layers:* Various layers that provide software, machine, and
+ distro metadata.
+
+- *Source Files:* Upstream releases, local projects, and SCMs.
+
+- *Build System:* Processes under the control of
+ :term:`BitBake`. This block expands
+ on how BitBake fetches source, applies patches, completes
+ compilation, analyzes output for package generation, creates and
+ tests packages, generates images, and generates cross-development
+ tools.
+
+- *Package Feeds:* Directories containing output packages (RPM, DEB or
+ IPK), which are subsequently used in the construction of an image or
+ Software Development Kit (SDK), produced by the build system. These
+ feeds can also be copied and shared using a web server or other means
+ to facilitate extending or updating existing images on devices at
+ runtime if runtime package management is enabled.
+
+- *Images:* Images produced by the workflow.
+
+- *Application Development SDK:* Cross-development tools that are
+ produced along with an image or separately with BitBake.
+
+User Configuration
+------------------
+
+User configuration helps define the build. Through user configuration,
+you can tell BitBake the target architecture for which you are building
+the image, where to store downloaded source, and other build properties.
+
+The following figure shows an expanded representation of the "User
+Configuration" box of the `general workflow
+figure <#general-workflow-figure>`__:
+
+.. image:: figures/user-configuration.png
+ :align: center
+
+BitBake needs some basic configuration files in order to complete a
+build. These files are ``*.conf`` files. The minimally necessary ones
+reside as example files in the ``build/conf`` directory of the
+:term:`Source Directory`. For simplicity,
+this section refers to the Source Directory as the "Poky Directory."
+
+When you clone the :term:`Poky` Git repository
+or you download and unpack a Yocto Project release, you can set up the
+Source Directory to be named anything you want. For this discussion, the
+cloned repository uses the default name ``poky``.
+
+.. note::
+
+ The Poky repository is primarily an aggregation of existing
+ repositories. It is not a canonical upstream source.
+
+The ``meta-poky`` layer inside Poky contains a ``conf`` directory that
+has example configuration files. These example files are used as a basis
+for creating actual configuration files when you source
+:ref:`structure-core-script`, which is the
+build environment script.
+
+Sourcing the build environment script creates a
+:term:`Build Directory` if one does not
+already exist. BitBake uses the Build Directory for all its work during
+builds. The Build Directory has a ``conf`` directory that contains
+default versions of your ``local.conf`` and ``bblayers.conf``
+configuration files. These default configuration files are created only
+if versions do not already exist in the Build Directory at the time you
+source the build environment setup script.
+
+Because the Poky repository is fundamentally an aggregation of existing
+repositories, some users might be familiar with running the
+:ref:`structure-core-script` script in the context of separate
+:term:`OpenEmbedded-Core (OE-Core)` and BitBake
+repositories rather than a single Poky repository. This discussion
+assumes the script is executed from within a cloned or unpacked version
+of Poky.
+
+Depending on where the script is sourced, different sub-scripts are
+called to set up the Build Directory (Yocto or OpenEmbedded).
+Specifically, the script ``scripts/oe-setup-builddir`` inside the poky
+directory sets up the Build Directory and seeds the directory (if
+necessary) with configuration files appropriate for the Yocto Project
+development environment.
+
+.. note::
+
+ The
+ scripts/oe-setup-builddir
+ script uses the
+ ``$TEMPLATECONF``
+ variable to determine which sample configuration files to locate.
+
+The ``local.conf`` file provides many basic variables that define a
+build environment. Here is a list of a few. To see the default
+configurations in a ``local.conf`` file created by the build environment
+script, see the
+:yocto_git:`local.conf.sample </cgit/cgit.cgi/poky/tree/meta-poky/conf/local.conf.sample>`
+in the ``meta-poky`` layer:
+
+- *Target Machine Selection:* Controlled by the
+ :term:`MACHINE` variable.
+
+- *Download Directory:* Controlled by the
+ :term:`DL_DIR` variable.
+
+- *Shared State Directory:* Controlled by the
+ :term:`SSTATE_DIR` variable.
+
+- *Build Output:* Controlled by the
+ :term:`TMPDIR` variable.
+
+- *Distribution Policy:* Controlled by the
+ :term:`DISTRO` variable.
+
+- *Packaging Format:* Controlled by the
+ :term:`PACKAGE_CLASSES`
+ variable.
+
+- *SDK Target Architecture:* Controlled by the
+ :term:`SDKMACHINE` variable.
+
+- *Extra Image Packages:* Controlled by the
+ :term:`EXTRA_IMAGE_FEATURES`
+ variable.
+
+.. note::
+
+ Configurations set in the
+ conf/local.conf
+ file can also be set in the
+ conf/site.conf
+ and
+ conf/auto.conf
+ configuration files.
+
+The ``bblayers.conf`` file tells BitBake what layers you want considered
+during the build. By default, the layers listed in this file include
+layers minimally needed by the build system. However, you must manually
+add any custom layers you have created. You can find more information on
+working with the ``bblayers.conf`` file in the
+":ref:`dev-manual/dev-manual-common-tasks:enabling your layer`"
+section in the Yocto Project Development Tasks Manual.
+
+The files ``site.conf`` and ``auto.conf`` are not created by the
+environment initialization script. If you want the ``site.conf`` file,
+you need to create that yourself. The ``auto.conf`` file is typically
+created by an autobuilder:
+
+- *site.conf:* You can use the ``conf/site.conf`` configuration
+ file to configure multiple build directories. For example, suppose
+ you had several build environments and they shared some common
+ features. You can set these default build properties here. A good
+ example is perhaps the packaging format to use through the
+ :term:`PACKAGE_CLASSES`
+ variable.
+
+ One useful scenario for using the ``conf/site.conf`` file is to
+ extend your :term:`BBPATH` variable
+ to include the path to a ``conf/site.conf``. Then, when BitBake looks
+ for Metadata using ``BBPATH``, it finds the ``conf/site.conf`` file
+ and applies your common configurations found in the file. To override
+ configurations in a particular build directory, alter the similar
+ configurations within that build directory's ``conf/local.conf``
+ file.
+
+- *auto.conf:* The file is usually created and written to by an
+ autobuilder. The settings put into the file are typically the same as
+ you would find in the ``conf/local.conf`` or the ``conf/site.conf``
+ files.
+
+You can edit all configuration files to further define any particular
+build environment. This process is represented by the "User
+Configuration Edits" box in the figure.
+
+When you launch your build with the ``bitbake target`` command, BitBake
+sorts out the configurations to ultimately define your build
+environment. It is important to understand that the
+:term:`OpenEmbedded Build System` reads the
+configuration files in a specific order: ``site.conf``, ``auto.conf``,
+and ``local.conf``. And, the build system applies the normal assignment
+statement rules as described in the
+":doc:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata`" chapter
+of the BitBake User Manual. Because the files are parsed in a specific
+order, variable assignments for the same variable could be affected. For
+example, if the ``auto.conf`` file and the ``local.conf`` set variable1
+to different values, because the build system parses ``local.conf``
+after ``auto.conf``, variable1 is assigned the value from the
+``local.conf`` file.
+
+Metadata, Machine Configuration, and Policy Configuration
+---------------------------------------------------------
+
+The previous section described the user configurations that define
+BitBake's global behavior. This section takes a closer look at the
+layers the build system uses to further control the build. These layers
+provide Metadata for the software, machine, and policies.
+
+In general, three types of layer input exists. You can see them below
+the "User Configuration" box in the `general workflow
+figure <#general-workflow-figure>`__:
+
+- *Metadata (.bb + Patches):* Software layers containing
+ user-supplied recipe files, patches, and append files. A good example
+ of a software layer might be the
+ `meta-qt5 layer <https://github.com/meta-qt5/meta-qt5>`__ from
+ the `OpenEmbedded Layer
+ Index <http://layers.openembedded.org/layerindex/branch/master/layers/>`__.
+ This layer is for version 5.0 of the popular
+ `Qt <https://wiki.qt.io/About_Qt>`__ cross-platform application
+ development framework for desktop, embedded and mobile.
+
+- *Machine BSP Configuration:* Board Support Package (BSP) layers (i.e.
+ "BSP Layer" in the following figure) providing machine-specific
+ configurations. This type of information is specific to a particular
+ target architecture. A good example of a BSP layer from the `Poky
+ Reference Distribution <#gs-reference-distribution-poky>`__ is the
+ :yocto_git:`meta-yocto-bsp </cgit/cgit.cgi/poky/tree/meta-yocto-bsp>`
+ layer.
+
+- *Policy Configuration:* Distribution Layers (i.e. "Distro Layer" in
+ the following figure) providing top-level or general policies for the
+ images or SDKs being built for a particular distribution. For
+ example, in the Poky Reference Distribution the distro layer is the
+ :yocto_git:`meta-poky </cgit/cgit.cgi/poky/tree/meta-poky>`
+ layer. Within the distro layer is a ``conf/distro`` directory that
+ contains distro configuration files (e.g.
+ :yocto_git:`poky.conf </cgit/cgit.cgi/poky/tree/meta-poky/conf/distro/poky.conf>`
+ that contain many policy configurations for the Poky distribution.
+
+The following figure shows an expanded representation of these three
+layers from the `general workflow figure <#general-workflow-figure>`__:
+
+.. image:: figures/layer-input.png
+ :align: center
+
+In general, all layers have a similar structure. They all contain a
+licensing file (e.g. ``COPYING.MIT``) if the layer is to be distributed,
+a ``README`` file as good practice and especially if the layer is to be
+distributed, a configuration directory, and recipe directories. You can
+learn about the general structure for layers used with the Yocto Project
+in the
+":ref:`dev-manual/dev-manual-common-tasks:creating your own layer`"
+section in the
+Yocto Project Development Tasks Manual. For a general discussion on
+layers and the many layers from which you can draw, see the
+"`Layers <#overview-layers>`__" and "`The Yocto Project Layer
+Model <#the-yocto-project-layer-model>`__" sections both earlier in this
+manual.
+
+If you explored the previous links, you discovered some areas where many
+layers that work with the Yocto Project exist. The `Source
+Repositories <http://git.yoctoproject.org/>`__ also shows layers
+categorized under "Yocto Metadata Layers."
+
+.. note::
+
+ Layers exist in the Yocto Project Source Repositories that cannot be
+ found in the OpenEmbedded Layer Index. These layers are either
+ deprecated or experimental in nature.
+
+BitBake uses the ``conf/bblayers.conf`` file, which is part of the user
+configuration, to find what layers it should be using as part of the
+build.
+
+Distro Layer
+~~~~~~~~~~~~
+
+The distribution layer provides policy configurations for your
+distribution. Best practices dictate that you isolate these types of
+configurations into their own layer. Settings you provide in
+``conf/distro/distro.conf`` override similar settings that BitBake finds
+in your ``conf/local.conf`` file in the Build Directory.
+
+The following list provides some explanation and references for what you
+typically find in the distribution layer:
+
+- *classes:* Class files (``.bbclass``) hold common functionality that
+ can be shared among recipes in the distribution. When your recipes
+ inherit a class, they take on the settings and functions for that
+ class. You can read more about class files in the
+ ":ref:`ref-manual/ref-classes:Classes`" chapter of the Yocto
+ Reference Manual.
+
+- *conf:* This area holds configuration files for the layer
+ (``conf/layer.conf``), the distribution
+ (``conf/distro/distro.conf``), and any distribution-wide include
+ files.
+
+- *recipes-*:* Recipes and append files that affect common
+ functionality across the distribution. This area could include
+ recipes and append files to add distribution-specific configuration,
+ initialization scripts, custom image recipes, and so forth. Examples
+ of ``recipes-*`` directories are ``recipes-core`` and
+ ``recipes-extra``. Hierarchy and contents within a ``recipes-*``
+ directory can vary. Generally, these directories contain recipe files
+ (``*.bb``), recipe append files (``*.bbappend``), directories that
+ are distro-specific for configuration files, and so forth.
+
+BSP Layer
+~~~~~~~~~
+
+The BSP Layer provides machine configurations that target specific
+hardware. Everything in this layer is specific to the machine for which
+you are building the image or the SDK. A common structure or form is
+defined for BSP layers. You can learn more about this structure in the
+:doc:`../bsp-guide/bsp-guide`.
+
+.. note::
+
+ In order for a BSP layer to be considered compliant with the Yocto
+ Project, it must meet some structural requirements.
+
+The BSP Layer's configuration directory contains configuration files for
+the machine (``conf/machine/machine.conf``) and, of course, the layer
+(``conf/layer.conf``).
+
+The remainder of the layer is dedicated to specific recipes by function:
+``recipes-bsp``, ``recipes-core``, ``recipes-graphics``,
+``recipes-kernel``, and so forth. Metadata can exist for multiple
+formfactors, graphics support systems, and so forth.
+
+.. note::
+
+ While the figure shows several
+ recipes-\*
+ directories, not all these directories appear in all BSP layers.
+
+Software Layer
+~~~~~~~~~~~~~~
+
+The software layer provides the Metadata for additional software
+packages used during the build. This layer does not include Metadata
+that is specific to the distribution or the machine, which are found in
+their respective layers.
+
+This layer contains any recipes, append files, and patches, that your
+project needs.
+
+.. _sources-dev-environment:
+
+Sources
+-------
+
+In order for the OpenEmbedded build system to create an image or any
+target, it must be able to access source files. The `general workflow
+figure <#general-workflow-figure>`__ represents source files using the
+"Upstream Project Releases", "Local Projects", and "SCMs (optional)"
+boxes. The figure represents mirrors, which also play a role in locating
+source files, with the "Source Materials" box.
+
+The method by which source files are ultimately organized is a function
+of the project. For example, for released software, projects tend to use
+tarballs or other archived files that can capture the state of a release
+guaranteeing that it is statically represented. On the other hand, for a
+project that is more dynamic or experimental in nature, a project might
+keep source files in a repository controlled by a Source Control Manager
+(SCM) such as Git. Pulling source from a repository allows you to
+control the point in the repository (the revision) from which you want
+to build software. Finally, a combination of the two might exist, which
+would give the consumer a choice when deciding where to get source
+files.
+
+BitBake uses the :term:`SRC_URI`
+variable to point to source files regardless of their location. Each
+recipe must have a ``SRC_URI`` variable that points to the source.
+
+Another area that plays a significant role in where source files come
+from is pointed to by the
+:term:`DL_DIR` variable. This area is
+a cache that can hold previously downloaded source. You can also
+instruct the OpenEmbedded build system to create tarballs from Git
+repositories, which is not the default behavior, and store them in the
+``DL_DIR`` by using the
+:term:`BB_GENERATE_MIRROR_TARBALLS`
+variable.
+
+Judicious use of a ``DL_DIR`` directory can save the build system a trip
+across the Internet when looking for files. A good method for using a
+download directory is to have ``DL_DIR`` point to an area outside of
+your Build Directory. Doing so allows you to safely delete the Build
+Directory if needed without fear of removing any downloaded source file.
+
+The remainder of this section provides a deeper look into the source
+files and the mirrors. Here is a more detailed look at the source file
+area of the `general workflow figure <#general-workflow-figure>`__:
+
+.. image:: figures/source-input.png
+ :align: center
+
+Upstream Project Releases
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Upstream project releases exist anywhere in the form of an archived file
+(e.g. tarball or zip file). These files correspond to individual
+recipes. For example, the figure uses specific releases each for
+BusyBox, Qt, and Dbus. An archive file can be for any released product
+that can be built using a recipe.
+
+Local Projects
+~~~~~~~~~~~~~~
+
+Local projects are custom bits of software the user provides. These bits
+reside somewhere local to a project - perhaps a directory into which the
+user checks in items (e.g. a local directory containing a development
+source tree used by the group).
+
+The canonical method through which to include a local project is to use
+the :ref:`externalsrc <ref-classes-externalsrc>`
+class to include that local project. You use either the ``local.conf``
+or a recipe's append file to override or set the recipe to point to the
+local directory on your disk to pull in the whole source tree.
+
+.. _scms:
+
+Source Control Managers (Optional)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Another place from which the build system can get source files is with
+:ref:`fetchers <bitbake:bb-fetchers>` employing various Source
+Control Managers (SCMs) such as Git or Subversion. In such cases, a
+repository is cloned or checked out. The
+:ref:`ref-tasks-fetch` task inside
+BitBake uses the :term:`SRC_URI`
+variable and the argument's prefix to determine the correct fetcher
+module.
+
+.. note::
+
+ For information on how to have the OpenEmbedded build system generate
+ tarballs for Git repositories and place them in the
+ DL_DIR
+ directory, see the :term:`BB_GENERATE_MIRROR_TARBALLS`
+ variable in the Yocto Project Reference Manual.
+
+When fetching a repository, BitBake uses the
+:term:`SRCREV` variable to determine
+the specific revision from which to build.
+
+Source Mirror(s)
+~~~~~~~~~~~~~~~~
+
+Two kinds of mirrors exist: pre-mirrors and regular mirrors. The
+:term:`PREMIRRORS` and
+:term:`MIRRORS` variables point to
+these, respectively. BitBake checks pre-mirrors before looking upstream
+for any source files. Pre-mirrors are appropriate when you have a shared
+directory that is not a directory defined by the
+:term:`DL_DIR` variable. A Pre-mirror
+typically points to a shared directory that is local to your
+organization.
+
+Regular mirrors can be any site across the Internet that is used as an
+alternative location for source code should the primary site not be
+functioning for some reason or another.
+
+.. _package-feeds-dev-environment:
+
+Package Feeds
+-------------
+
+When the OpenEmbedded build system generates an image or an SDK, it gets
+the packages from a package feed area located in the
+:term:`Build Directory`. The `general
+workflow figure <#general-workflow-figure>`__ shows this package feeds
+area in the upper-right corner.
+
+This section looks a little closer into the package feeds area used by
+the build system. Here is a more detailed look at the area:
+
+.. image:: figures/package-feeds.png
+ :align: center
+
+Package feeds are an intermediary step in the build process. The
+OpenEmbedded build system provides classes to generate different package
+types, and you specify which classes to enable through the
+:term:`PACKAGE_CLASSES`
+variable. Before placing the packages into package feeds, the build
+process validates them with generated output quality assurance checks
+through the :ref:`insane <ref-classes-insane>`
+class.
+
+The package feed area resides in the Build Directory. The directory the
+build system uses to temporarily store packages is determined by a
+combination of variables and the particular package manager in use. See
+the "Package Feeds" box in the illustration and note the information to
+the right of that area. In particular, the following defines where
+package files are kept:
+
+- :term:`DEPLOY_DIR`: Defined as
+ ``tmp/deploy`` in the Build Directory.
+
+- ``DEPLOY_DIR_*``: Depending on the package manager used, the package
+ type sub-folder. Given RPM, IPK, or DEB packaging and tarball
+ creation, the
+ :term:`DEPLOY_DIR_RPM`,
+ :term:`DEPLOY_DIR_IPK`,
+ :term:`DEPLOY_DIR_DEB`, or
+ :term:`DEPLOY_DIR_TAR`,
+ variables are used, respectively.
+
+- :term:`PACKAGE_ARCH`: Defines
+ architecture-specific sub-folders. For example, packages could exist
+ for the i586 or qemux86 architectures.
+
+BitBake uses the
+:ref:`do_package_write_* <ref-tasks-package_write_deb>`
+tasks to generate packages and place them into the package holding area
+(e.g. ``do_package_write_ipk`` for IPK packages). See the
+":ref:`ref-tasks-package_write_deb`",
+":ref:`ref-tasks-package_write_ipk`",
+":ref:`ref-tasks-package_write_rpm`",
+and
+":ref:`ref-tasks-package_write_tar`"
+sections in the Yocto Project Reference Manual for additional
+information. As an example, consider a scenario where an IPK packaging
+manager is being used and package architecture support for both i586 and
+qemux86 exist. Packages for the i586 architecture are placed in
+``build/tmp/deploy/ipk/i586``, while packages for the qemux86
+architecture are placed in ``build/tmp/deploy/ipk/qemux86``.
+
+.. _bitbake-dev-environment:
+
+BitBake Tool
+------------
+
+The OpenEmbedded build system uses
+:term:`BitBake` to produce images and
+Software Development Kits (SDKs). You can see from the `general workflow
+figure <#general-workflow-figure>`__, the BitBake area consists of
+several functional areas. This section takes a closer look at each of
+those areas.
+
+.. note::
+
+ Separate documentation exists for the BitBake tool. See the
+ BitBake User Manual
+ for reference material on BitBake.
+
+.. _source-fetching-dev-environment:
+
+Source Fetching
+~~~~~~~~~~~~~~~
+
+The first stages of building a recipe are to fetch and unpack the source
+code:
+
+.. image:: figures/source-fetching.png
+ :align: center
+
+The :ref:`ref-tasks-fetch` and
+:ref:`ref-tasks-unpack` tasks fetch
+the source files and unpack them into the
+:term:`Build Directory`.
+
+.. note::
+
+ For every local file (e.g.
+ file://
+ ) that is part of a recipe's
+ SRC_URI
+ statement, the OpenEmbedded build system takes a checksum of the file
+ for the recipe and inserts the checksum into the signature for the
+ do_fetch
+ task. If any local file has been modified, the
+ do_fetch
+ task and all tasks that depend on it are re-executed.
+
+By default, everything is accomplished in the Build Directory, which has
+a defined structure. For additional general information on the Build
+Directory, see the ":ref:`structure-core-build`" section in
+the Yocto Project Reference Manual.
+
+Each recipe has an area in the Build Directory where the unpacked source
+code resides. The :term:`S` variable points
+to this area for a recipe's unpacked source code. The name of that
+directory for any given recipe is defined from several different
+variables. The preceding figure and the following list describe the
+Build Directory's hierarchy:
+
+- :term:`TMPDIR`: The base directory
+ where the OpenEmbedded build system performs all its work during the
+ build. The default base directory is the ``tmp`` directory.
+
+- :term:`PACKAGE_ARCH`: The
+ architecture of the built package or packages. Depending on the
+ eventual destination of the package or packages (i.e. machine
+ architecture, :term:`Build Host`, SDK, or
+ specific machine), ``PACKAGE_ARCH`` varies. See the variable's
+ description for details.
+
+- :term:`TARGET_OS`: The operating
+ system of the target device. A typical value would be "linux" (e.g.
+ "qemux86-poky-linux").
+
+- :term:`PN`: The name of the recipe used
+ to build the package. This variable can have multiple meanings.
+ However, when used in the context of input files, ``PN`` represents
+ the name of the recipe.
+
+- :term:`WORKDIR`: The location
+ where the OpenEmbedded build system builds a recipe (i.e. does the
+ work to create the package).
+
+ - :term:`PV`: The version of the
+ recipe used to build the package.
+
+ - :term:`PR`: The revision of the
+ recipe used to build the package.
+
+- :term:`S`: Contains the unpacked source
+ files for a given recipe.
+
+ - :term:`BPN`: The name of the recipe
+ used to build the package. The ``BPN`` variable is a version of
+ the ``PN`` variable but with common prefixes and suffixes removed.
+
+ - :term:`PV`: The version of the
+ recipe used to build the package.
+
+.. note::
+
+ In the previous figure, notice that two sample hierarchies exist: one
+ based on package architecture (i.e.
+ PACKAGE_ARCH
+ ) and one based on a machine (i.e.
+ MACHINE
+ ). The underlying structures are identical. The differentiator being
+ what the OpenEmbedded build system is using as a build target (e.g.
+ general architecture, a build host, an SDK, or a specific machine).
+
+.. _patching-dev-environment:
+
+Patching
+~~~~~~~~
+
+Once source code is fetched and unpacked, BitBake locates patch files
+and applies them to the source files:
+
+.. image:: figures/patching.png
+ :align: center
+
+The :ref:`ref-tasks-patch` task uses a
+recipe's :term:`SRC_URI` statements
+and the :term:`FILESPATH` variable
+to locate applicable patch files.
+
+Default processing for patch files assumes the files have either
+``*.patch`` or ``*.diff`` file types. You can use ``SRC_URI`` parameters
+to change the way the build system recognizes patch files. See the
+:ref:`ref-tasks-patch` task for more
+information.
+
+BitBake finds and applies multiple patches for a single recipe in the
+order in which it locates the patches. The ``FILESPATH`` variable
+defines the default set of directories that the build system uses to
+search for patch files. Once found, patches are applied to the recipe's
+source files, which are located in the
+:term:`S` directory.
+
+For more information on how the source directories are created, see the
+"`Source Fetching <#source-fetching-dev-environment>`__" section. For
+more information on how to create patches and how the build system
+processes patches, see the
+":ref:`dev-manual/dev-manual-common-tasks:patching code`"
+section in the
+Yocto Project Development Tasks Manual. You can also see the
+":ref:`sdk-manual/sdk-extensible:use \`\`devtool modify\`\` to modify the source of an existing component`"
+section in the Yocto Project Application Development and the Extensible
+Software Development Kit (SDK) manual and the
+":ref:`kernel-dev/kernel-dev-common:using traditional kernel development to patch the kernel`"
+section in the Yocto Project Linux Kernel Development Manual.
+
+.. _configuration-compilation-and-staging-dev-environment:
+
+Configuration, Compilation, and Staging
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+After source code is patched, BitBake executes tasks that configure and
+compile the source code. Once compilation occurs, the files are copied
+to a holding area (staged) in preparation for packaging:
+
+.. image:: figures/configuration-compile-autoreconf.png
+ :align: center
+
+This step in the build process consists of the following tasks:
+
+- :ref:`ref-tasks-prepare_recipe_sysroot`:
+ This task sets up the two sysroots in
+ ``${``\ :term:`WORKDIR`\ ``}``
+ (i.e. ``recipe-sysroot`` and ``recipe-sysroot-native``) so that
+ during the packaging phase the sysroots can contain the contents of
+ the
+ :ref:`ref-tasks-populate_sysroot`
+ tasks of the recipes on which the recipe containing the tasks
+ depends. A sysroot exists for both the target and for the native
+ binaries, which run on the host system.
+
+- *do_configure*: This task configures the source by enabling and
+ disabling any build-time and configuration options for the software
+ being built. Configurations can come from the recipe itself as well
+ as from an inherited class. Additionally, the software itself might
+ configure itself depending on the target for which it is being built.
+
+ The configurations handled by the
+ :ref:`ref-tasks-configure` task
+ are specific to configurations for the source code being built by the
+ recipe.
+
+ If you are using the
+ :ref:`autotools <ref-classes-autotools>` class,
+ you can add additional configuration options by using the
+ :term:`EXTRA_OECONF` or
+ :term:`PACKAGECONFIG_CONFARGS`
+ variables. For information on how this variable works within that
+ class, see the
+ :ref:`autotools <ref-classes-autotools>` class
+ :yocto_git:`here </cgit/cgit.cgi/poky/tree/meta/classes/autotools.bbclass>`.
+
+- *do_compile*: Once a configuration task has been satisfied,
+ BitBake compiles the source using the
+ :ref:`ref-tasks-compile` task.
+ Compilation occurs in the directory pointed to by the
+ :term:`B` variable. Realize that the
+ ``B`` directory is, by default, the same as the
+ :term:`S` directory.
+
+- *do_install*: After compilation completes, BitBake executes the
+ :ref:`ref-tasks-install` task.
+ This task copies files from the ``B`` directory and places them in a
+ holding area pointed to by the :term:`D`
+ variable. Packaging occurs later using files from this holding
+ directory.
+
+.. _package-splitting-dev-environment:
+
+Package Splitting
+~~~~~~~~~~~~~~~~~
+
+After source code is configured, compiled, and staged, the build system
+analyzes the results and splits the output into packages:
+
+.. image:: figures/analysis-for-package-splitting.png
+ :align: center
+
+The :ref:`ref-tasks-package` and
+:ref:`ref-tasks-packagedata`
+tasks combine to analyze the files found in the
+:term:`D` directory and split them into
+subsets based on available packages and files. Analysis involves the
+following as well as other items: splitting out debugging symbols,
+looking at shared library dependencies between packages, and looking at
+package relationships.
+
+The ``do_packagedata`` task creates package metadata based on the
+analysis such that the build system can generate the final packages. The
+:ref:`ref-tasks-populate_sysroot`
+task stages (copies) a subset of the files installed by the
+:ref:`ref-tasks-install` task into
+the appropriate sysroot. Working, staged, and intermediate results of
+the analysis and package splitting process use several areas:
+
+- :term:`PKGD`: The destination
+ directory (i.e. ``package``) for packages before they are split into
+ individual packages.
+
+- :term:`PKGDESTWORK`: A
+ temporary work area (i.e. ``pkgdata``) used by the ``do_package``
+ task to save package metadata.
+
+- :term:`PKGDEST`: The parent
+ directory (i.e. ``packages-split``) for packages after they have been
+ split.
+
+- :term:`PKGDATA_DIR`: A shared,
+ global-state directory that holds packaging metadata generated during
+ the packaging process. The packaging process copies metadata from
+ ``PKGDESTWORK`` to the ``PKGDATA_DIR`` area where it becomes globally
+ available.
+
+- :term:`STAGING_DIR_HOST`:
+ The path for the sysroot for the system on which a component is built
+ to run (i.e. ``recipe-sysroot``).
+
+- :term:`STAGING_DIR_NATIVE`:
+ The path for the sysroot used when building components for the build
+ host (i.e. ``recipe-sysroot-native``).
+
+- :term:`STAGING_DIR_TARGET`:
+ The path for the sysroot used when a component that is built to
+ execute on a system and it generates code for yet another machine
+ (e.g. cross-canadian recipes).
+
+The :term:`FILES` variable defines the
+files that go into each package in
+:term:`PACKAGES`. If you want
+details on how this is accomplished, you can look at
+:yocto_git:`package.bbclass </cgit/cgit.cgi/poky/tree/meta/classes/package.bbclass>`.
+
+Depending on the type of packages being created (RPM, DEB, or IPK), the
+:ref:`do_package_write_* <ref-tasks-package_write_deb>`
+task creates the actual packages and places them in the Package Feed
+area, which is ``${TMPDIR}/deploy``. You can see the "`Package
+Feeds <#package-feeds-dev-environment>`__" section for more detail on
+that part of the build process.
+
+.. note::
+
+ Support for creating feeds directly from the
+ deploy/\*
+ directories does not exist. Creating such feeds usually requires some
+ kind of feed maintenance mechanism that would upload the new packages
+ into an official package feed (e.g. the Ångström distribution). This
+ functionality is highly distribution-specific and thus is not
+ provided out of the box.
+
+.. _image-generation-dev-environment:
+
+Image Generation
+~~~~~~~~~~~~~~~~
+
+Once packages are split and stored in the Package Feeds area, the build
+system uses BitBake to generate the root filesystem image:
+
+.. image:: figures/image-generation.png
+ :align: center
+
+The image generation process consists of several stages and depends on
+several tasks and variables. The
+:ref:`ref-tasks-rootfs` task creates
+the root filesystem (file and directory structure) for an image. This
+task uses several key variables to help create the list of packages to
+actually install:
+
+- :term:`IMAGE_INSTALL`: Lists
+ out the base set of packages from which to install from the Package
+ Feeds area.
+
+- :term:`PACKAGE_EXCLUDE`:
+ Specifies packages that should not be installed into the image.
+
+- :term:`IMAGE_FEATURES`:
+ Specifies features to include in the image. Most of these features
+ map to additional packages for installation.
+
+- :term:`PACKAGE_CLASSES`:
+ Specifies the package backend (e.g. RPM, DEB, or IPK) to use and
+ consequently helps determine where to locate packages within the
+ Package Feeds area.
+
+- :term:`IMAGE_LINGUAS`:
+ Determines the language(s) for which additional language support
+ packages are installed.
+
+- :term:`PACKAGE_INSTALL`:
+ The final list of packages passed to the package manager for
+ installation into the image.
+
+With :term:`IMAGE_ROOTFS`
+pointing to the location of the filesystem under construction and the
+``PACKAGE_INSTALL`` variable providing the final list of packages to
+install, the root file system is created.
+
+Package installation is under control of the package manager (e.g.
+dnf/rpm, opkg, or apt/dpkg) regardless of whether or not package
+management is enabled for the target. At the end of the process, if
+package management is not enabled for the target, the package manager's
+data files are deleted from the root filesystem. As part of the final
+stage of package installation, post installation scripts that are part
+of the packages are run. Any scripts that fail to run on the build host
+are run on the target when the target system is first booted. If you are
+using a
+:ref:`read-only root filesystem <dev-manual/dev-manual-common-tasks:creating a read-only root filesystem>`,
+all the post installation scripts must succeed on the build host during
+the package installation phase since the root filesystem on the target
+is read-only.
+
+The final stages of the ``do_rootfs`` task handle post processing. Post
+processing includes creation of a manifest file and optimizations.
+
+The manifest file (``.manifest``) resides in the same directory as the
+root filesystem image. This file lists out, line-by-line, the installed
+packages. The manifest file is useful for the
+:ref:`testimage <ref-classes-testimage*>` class,
+for example, to determine whether or not to run specific tests. See the
+:term:`IMAGE_MANIFEST`
+variable for additional information.
+
+Optimizing processes that are run across the image include ``mklibs``,
+``prelink``, and any other post-processing commands as defined by the
+:term:`ROOTFS_POSTPROCESS_COMMAND`
+variable. The ``mklibs`` process optimizes the size of the libraries,
+while the ``prelink`` process optimizes the dynamic linking of shared
+libraries to reduce start up time of executables.
+
+After the root filesystem is built, processing begins on the image
+through the :ref:`ref-tasks-image`
+task. The build system runs any pre-processing commands as defined by
+the
+:term:`IMAGE_PREPROCESS_COMMAND`
+variable. This variable specifies a list of functions to call before the
+build system creates the final image output files.
+
+The build system dynamically creates ``do_image_*`` tasks as needed,
+based on the image types specified in the
+:term:`IMAGE_FSTYPES` variable.
+The process turns everything into an image file or a set of image files
+and can compress the root filesystem image to reduce the overall size of
+the image. The formats used for the root filesystem depend on the
+``IMAGE_FSTYPES`` variable. Compression depends on whether the formats
+support compression.
+
+As an example, a dynamically created task when creating a particular
+image type would take the following form:
+::
+
+ do_image_type
+
+So, if the type
+as specified by the ``IMAGE_FSTYPES`` were ``ext4``, the dynamically
+generated task would be as follows:
+::
+
+ do_image_ext4
+
+The final task involved in image creation is the
+:ref:`do_image_complete <ref-tasks-image-complete>`
+task. This task completes the image by applying any image post
+processing as defined through the
+:term:`IMAGE_POSTPROCESS_COMMAND`
+variable. The variable specifies a list of functions to call once the
+build system has created the final image output files.
+
+.. note::
+
+ The entire image generation process is run under
+ Pseudo. Running under Pseudo ensures that the files in the root filesystem
+ have correct ownership.
+
+.. _sdk-generation-dev-environment:
+
+SDK Generation
+~~~~~~~~~~~~~~
+
+The OpenEmbedded build system uses BitBake to generate the Software
+Development Kit (SDK) installer scripts for both the standard SDK and
+the extensible SDK (eSDK):
+
+.. image:: figures/sdk-generation.png
+ :align: center
+
+.. note::
+
+ For more information on the cross-development toolchain generation,
+ see the ":ref:`overview-manual/overview-manual-concepts:cross-development toolchain generation`"
+ section. For information on advantages gained when building a
+ cross-development toolchain using the do_populate_sdk task, see the
+ ":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`" section in
+ the Yocto Project Application Development and the Extensible Software
+ Development Kit (eSDK) manual.
+
+Like image generation, the SDK script process consists of several stages
+and depends on many variables. The
+:ref:`ref-tasks-populate_sdk`
+and
+:ref:`ref-tasks-populate_sdk_ext`
+tasks use these key variables to help create the list of packages to
+actually install. For information on the variables listed in the figure,
+see the "`Application Development SDK <#sdk-dev-environment>`__"
+section.
+
+The ``do_populate_sdk`` task helps create the standard SDK and handles
+two parts: a target part and a host part. The target part is the part
+built for the target hardware and includes libraries and headers. The
+host part is the part of the SDK that runs on the
+:term:`SDKMACHINE`.
+
+The ``do_populate_sdk_ext`` task helps create the extensible SDK and
+handles host and target parts differently than its counter part does for
+the standard SDK. For the extensible SDK, the task encapsulates the
+build system, which includes everything needed (host and target) for the
+SDK.
+
+Regardless of the type of SDK being constructed, the tasks perform some
+cleanup after which a cross-development environment setup script and any
+needed configuration files are created. The final output is the
+Cross-development toolchain installation script (``.sh`` file), which
+includes the environment setup script.
+
+Stamp Files and the Rerunning of Tasks
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+For each task that completes successfully, BitBake writes a stamp file
+into the :term:`STAMPS_DIR`
+directory. The beginning of the stamp file's filename is determined by
+the :term:`STAMP` variable, and the end
+of the name consists of the task's name and current `input
+checksum <#overview-checksums>`__.
+
+.. note::
+
+ This naming scheme assumes that
+ BB_SIGNATURE_HANDLER
+ is "OEBasicHash", which is almost always the case in current
+ OpenEmbedded.
+
+To determine if a task needs to be rerun, BitBake checks if a stamp file
+with a matching input checksum exists for the task. If such a stamp file
+exists, the task's output is assumed to exist and still be valid. If the
+file does not exist, the task is rerun.
+
+.. note::
+
+ The stamp mechanism is more general than the shared state (sstate)
+ cache mechanism described in the "`Setscene Tasks and Shared
+ State <#setscene-tasks-and-shared-state>`__" section. BitBake avoids
+ rerunning any task that has a valid stamp file, not just tasks that
+ can be accelerated through the sstate cache.
+
+ However, you should realize that stamp files only serve as a marker
+ that some work has been done and that these files do not record task
+ output. The actual task output would usually be somewhere in
+ :term:`TMPDIR` (e.g. in some
+ recipe's :term:`WORKDIR`.) What
+ the sstate cache mechanism adds is a way to cache task output that
+ can then be shared between build machines.
+
+Since ``STAMPS_DIR`` is usually a subdirectory of ``TMPDIR``, removing
+``TMPDIR`` will also remove ``STAMPS_DIR``, which means tasks will
+properly be rerun to repopulate ``TMPDIR``.
+
+If you want some task to always be considered "out of date", you can
+mark it with the :ref:`nostamp <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`
+varflag. If some other task depends on such a task, then that task will
+also always be considered out of date, which might not be what you want.
+
+For details on how to view information about a task's signature, see the
+":ref:`dev-manual/dev-manual-common-tasks:viewing task variable dependencies`"
+section in the Yocto Project Development Tasks Manual.
+
+Setscene Tasks and Shared State
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The description of tasks so far assumes that BitBake needs to build
+everything and no available prebuilt objects exist. BitBake does support
+skipping tasks if prebuilt objects are available. These objects are
+usually made available in the form of a shared state (sstate) cache.
+
+.. note::
+
+ For information on variables affecting sstate, see the
+ :term:`SSTATE_DIR`
+ and
+ :term:`SSTATE_MIRRORS`
+ variables.
+
+The idea of a setscene task (i.e ``do_``\ taskname\ ``_setscene``) is a
+version of the task where instead of building something, BitBake can
+skip to the end result and simply place a set of files into specific
+locations as needed. In some cases, it makes sense to have a setscene
+task variant (e.g. generating package files in the
+:ref:`do_package_write_* <ref-tasks-package_write_deb>`
+task). In other cases, it does not make sense (e.g. a
+:ref:`ref-tasks-patch` task or a
+:ref:`ref-tasks-unpack` task) since
+the work involved would be equal to or greater than the underlying task.
+
+In the build system, the common tasks that have setscene variants are
+:ref:`ref-tasks-package`,
+``do_package_write_*``,
+:ref:`ref-tasks-deploy`,
+:ref:`ref-tasks-packagedata`, and
+:ref:`ref-tasks-populate_sysroot`.
+Notice that these tasks represent most of the tasks whose output is an
+end result.
+
+The build system has knowledge of the relationship between these tasks
+and other preceding tasks. For example, if BitBake runs
+``do_populate_sysroot_setscene`` for something, it does not make sense
+to run any of the ``do_fetch``, ``do_unpack``, ``do_patch``,
+``do_configure``, ``do_compile``, and ``do_install`` tasks. However, if
+``do_package`` needs to be run, BitBake needs to run those other tasks.
+
+It becomes more complicated if everything can come from an sstate cache
+because some objects are simply not required at all. For example, you do
+not need a compiler or native tools, such as quilt, if nothing exists to
+compile or patch. If the ``do_package_write_*`` packages are available
+from sstate, BitBake does not need the ``do_package`` task data.
+
+To handle all these complexities, BitBake runs in two phases. The first
+is the "setscene" stage. During this stage, BitBake first checks the
+sstate cache for any targets it is planning to build. BitBake does a
+fast check to see if the object exists rather than a complete download.
+If nothing exists, the second phase, which is the setscene stage,
+completes and the main build proceeds.
+
+If objects are found in the sstate cache, the build system works
+backwards from the end targets specified by the user. For example, if an
+image is being built, the build system first looks for the packages
+needed for that image and the tools needed to construct an image. If
+those are available, the compiler is not needed. Thus, the compiler is
+not even downloaded. If something was found to be unavailable, or the
+download or setscene task fails, the build system then tries to install
+dependencies, such as the compiler, from the cache.
+
+The availability of objects in the sstate cache is handled by the
+function specified by the
+:term:`bitbake:BB_HASHCHECK_FUNCTION`
+variable and returns a list of available objects. The function specified
+by the
+:term:`bitbake:BB_SETSCENE_DEPVALID`
+variable is the function that determines whether a given dependency
+needs to be followed, and whether for any given relationship the
+function needs to be passed. The function returns a True or False value.
+
+.. _images-dev-environment:
+
+Images
+------
+
+The images produced by the build system are compressed forms of the root
+filesystem and are ready to boot on a target device. You can see from
+the `general workflow figure <#general-workflow-figure>`__ that BitBake
+output, in part, consists of images. This section takes a closer look at
+this output:
+
+.. image:: figures/images.png
+ :align: center
+
+.. note::
+
+ For a list of example images that the Yocto Project provides, see the
+ ":doc:`../ref-manual/ref-images`" chapter in the Yocto Project Reference
+ Manual.
+
+The build process writes images out to the :term:`Build Directory`
+inside the
+``tmp/deploy/images/machine/`` folder as shown in the figure. This
+folder contains any files expected to be loaded on the target device.
+The :term:`DEPLOY_DIR` variable
+points to the ``deploy`` directory, while the
+:term:`DEPLOY_DIR_IMAGE`
+variable points to the appropriate directory containing images for the
+current configuration.
+
+- kernel-image: A kernel binary file. The
+ :term:`KERNEL_IMAGETYPE`
+ variable determines the naming scheme for the kernel image file.
+ Depending on this variable, the file could begin with a variety of
+ naming strings. The ``deploy/images/``\ machine directory can contain
+ multiple image files for the machine.
+
+- root-filesystem-image: Root filesystems for the target device (e.g.
+ ``*.ext3`` or ``*.bz2`` files). The
+ :term:`IMAGE_FSTYPES`
+ variable determines the root filesystem image type. The
+ ``deploy/images/``\ machine directory can contain multiple root
+ filesystems for the machine.
+
+- kernel-modules: Tarballs that contain all the modules built for the
+ kernel. Kernel module tarballs exist for legacy purposes and can be
+ suppressed by setting the
+ :term:`MODULE_TARBALL_DEPLOY`
+ variable to "0". The ``deploy/images/``\ machine directory can
+ contain multiple kernel module tarballs for the machine.
+
+- bootloaders: If applicable to the target machine, bootloaders
+ supporting the image. The ``deploy/images/``\ machine directory can
+ contain multiple bootloaders for the machine.
+
+- symlinks: The ``deploy/images/``\ machine folder contains a symbolic
+ link that points to the most recently built file for each machine.
+ These links might be useful for external scripts that need to obtain
+ the latest version of each file.
+
+.. _sdk-dev-environment:
+
+Application Development SDK
+---------------------------
+
+In the `general workflow figure <#general-workflow-figure>`__, the
+output labeled "Application Development SDK" represents an SDK. The SDK
+generation process differs depending on whether you build an extensible
+SDK (e.g. ``bitbake -c populate_sdk_ext`` imagename) or a standard SDK
+(e.g. ``bitbake -c populate_sdk`` imagename). This section takes a
+closer look at this output:
+
+.. image:: figures/sdk.png
+ :align: center
+
+The specific form of this output is a set of files that includes a
+self-extracting SDK installer (``*.sh``), host and target manifest
+files, and files used for SDK testing. When the SDK installer file is
+run, it installs the SDK. The SDK consists of a cross-development
+toolchain, a set of libraries and headers, and an SDK environment setup
+script. Running this installer essentially sets up your
+cross-development environment. You can think of the cross-toolchain as
+the "host" part because it runs on the SDK machine. You can think of the
+libraries and headers as the "target" part because they are built for
+the target hardware. The environment setup script is added so that you
+can initialize the environment before using the tools.
+
+.. note::
+
+ - The Yocto Project supports several methods by which you can set up
+ this cross-development environment. These methods include
+ downloading pre-built SDK installers or building and installing
+ your own SDK installer.
+
+ - For background information on cross-development toolchains in the
+ Yocto Project development environment, see the "`Cross-Development
+ Toolchain Generation <#cross-development-toolchain-generation>`__"
+ section.
+
+ - For information on setting up a cross-development environment, see
+ the :doc:`../sdk-manual/sdk-manual` manual.
+
+All the output files for an SDK are written to the ``deploy/sdk`` folder
+inside the :term:`Build Directory` as
+shown in the previous figure. Depending on the type of SDK, several
+variables exist that help configure these files. The following list
+shows the variables associated with an extensible SDK:
+
+- :term:`DEPLOY_DIR`: Points to
+ the ``deploy`` directory.
+
+- :term:`SDK_EXT_TYPE`:
+ Controls whether or not shared state artifacts are copied into the
+ extensible SDK. By default, all required shared state artifacts are
+ copied into the SDK.
+
+- :term:`SDK_INCLUDE_PKGDATA`:
+ Specifies whether or not packagedata is included in the extensible
+ SDK for all recipes in the "world" target.
+
+- :term:`SDK_INCLUDE_TOOLCHAIN`:
+ Specifies whether or not the toolchain is included when building the
+ extensible SDK.
+
+- :term:`SDK_LOCAL_CONF_WHITELIST`:
+ A list of variables allowed through from the build system
+ configuration into the extensible SDK configuration.
+
+- :term:`SDK_LOCAL_CONF_BLACKLIST`:
+ A list of variables not allowed through from the build system
+ configuration into the extensible SDK configuration.
+
+- :term:`SDK_INHERIT_BLACKLIST`:
+ A list of classes to remove from the
+ :term:`INHERIT` value globally
+ within the extensible SDK configuration.
+
+This next list, shows the variables associated with a standard SDK:
+
+- :term:`DEPLOY_DIR`: Points to
+ the ``deploy`` directory.
+
+- :term:`SDKMACHINE`: Specifies
+ the architecture of the machine on which the cross-development tools
+ are run to create packages for the target hardware.
+
+- :term:`SDKIMAGE_FEATURES`:
+ Lists the features to include in the "target" part of the SDK.
+
+- :term:`TOOLCHAIN_HOST_TASK`:
+ Lists packages that make up the host part of the SDK (i.e. the part
+ that runs on the ``SDKMACHINE``). When you use
+ ``bitbake -c populate_sdk imagename`` to create the SDK, a set of
+ default packages apply. This variable allows you to add more
+ packages.
+
+- :term:`TOOLCHAIN_TARGET_TASK`:
+ Lists packages that make up the target part of the SDK (i.e. the part
+ built for the target hardware).
+
+- :term:`SDKPATH`: Defines the
+ default SDK installation path offered by the installation script.
+
+- :term:`SDK_HOST_MANIFEST`:
+ Lists all the installed packages that make up the host part of the
+ SDK. This variable also plays a minor role for extensible SDK
+ development as well. However, it is mainly used for the standard SDK.
+
+- :term:`SDK_TARGET_MANIFEST`:
+ Lists all the installed packages that make up the target part of the
+ SDK. This variable also plays a minor role for extensible SDK
+ development as well. However, it is mainly used for the standard SDK.
+
+Cross-Development Toolchain Generation
+======================================
+
+The Yocto Project does most of the work for you when it comes to
+creating :ref:`sdk-manual/sdk-intro:the cross-development toolchain`. This
+section provides some technical background on how cross-development
+toolchains are created and used. For more information on toolchains, you
+can also see the :doc:`../sdk-manual/sdk-manual` manual.
+
+In the Yocto Project development environment, cross-development
+toolchains are used to build images and applications that run on the
+target hardware. With just a few commands, the OpenEmbedded build system
+creates these necessary toolchains for you.
+
+The following figure shows a high-level build environment regarding
+toolchain construction and use.
+
+.. image:: figures/cross-development-toolchains.png
+ :align: center
+
+Most of the work occurs on the Build Host. This is the machine used to
+build images and generally work within the the Yocto Project
+environment. When you run
+:term:`BitBake` to create an image, the
+OpenEmbedded build system uses the host ``gcc`` compiler to bootstrap a
+cross-compiler named ``gcc-cross``. The ``gcc-cross`` compiler is what
+BitBake uses to compile source files when creating the target image. You
+can think of ``gcc-cross`` simply as an automatically generated
+cross-compiler that is used internally within BitBake only.
+
+.. note::
+
+ The extensible SDK does not use
+ gcc-cross-canadian
+ since this SDK ships a copy of the OpenEmbedded build system and the
+ sysroot within it contains
+ gcc-cross
+ .
+
+The chain of events that occurs when ``gcc-cross`` is bootstrapped is as
+follows:
+::
+
+ gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> glibc-initial -> glibc -> gcc-cross -> gcc-runtime
+
+- ``gcc``: The build host's GNU Compiler Collection (GCC).
+
+- ``binutils-cross``: The bare minimum binary utilities needed in order
+ to run the ``gcc-cross-initial`` phase of the bootstrap operation.
+
+- ``gcc-cross-initial``: An early stage of the bootstrap process for
+ creating the cross-compiler. This stage builds enough of the
+ ``gcc-cross``, the C library, and other pieces needed to finish
+ building the final cross-compiler in later stages. This tool is a
+ "native" package (i.e. it is designed to run on the build host).
+
+- ``linux-libc-headers``: Headers needed for the cross-compiler.
+
+- ``glibc-initial``: An initial version of the Embedded GNU C Library
+ (GLIBC) needed to bootstrap ``glibc``.
+
+- ``glibc``: The GNU C Library.
+
+- ``gcc-cross``: The final stage of the bootstrap process for the
+ cross-compiler. This stage results in the actual cross-compiler that
+ BitBake uses when it builds an image for a targeted device.
+
+ .. note::
+
+ If you are replacing this cross compiler toolchain with a custom
+ version, you must replace
+ gcc-cross
+ .
+
+ This tool is also a "native" package (i.e. it is designed to run on
+ the build host).
+
+- ``gcc-runtime``: Runtime libraries resulting from the toolchain
+ bootstrapping process. This tool produces a binary that consists of
+ the runtime libraries need for the targeted device.
+
+You can use the OpenEmbedded build system to build an installer for the
+relocatable SDK used to develop applications. When you run the
+installer, it installs the toolchain, which contains the development
+tools (e.g., ``gcc-cross-canadian``, ``binutils-cross-canadian``, and
+other ``nativesdk-*`` tools), which are tools native to the SDK (i.e.
+native to :term:`SDK_ARCH`), you
+need to cross-compile and test your software. The figure shows the
+commands you use to easily build out this toolchain. This
+cross-development toolchain is built to execute on the
+:term:`SDKMACHINE`, which might or
+might not be the same machine as the Build Host.
+
+.. note::
+
+ If your target architecture is supported by the Yocto Project, you
+ can take advantage of pre-built images that ship with the Yocto
+ Project and already contain cross-development toolchain installers.
+
+Here is the bootstrap process for the relocatable toolchain:
+::
+
+ gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers -> glibc-initial -> nativesdk-glibc -> gcc-crosssdk -> gcc-cross-canadian
+
+- ``gcc``: The build host's GNU Compiler Collection (GCC).
+
+- ``binutils-crosssdk``: The bare minimum binary utilities needed in
+ order to run the ``gcc-crosssdk-initial`` phase of the bootstrap
+ operation.
+
+- ``gcc-crosssdk-initial``: An early stage of the bootstrap process for
+ creating the cross-compiler. This stage builds enough of the
+ ``gcc-crosssdk`` and supporting pieces so that the final stage of the
+ bootstrap process can produce the finished cross-compiler. This tool
+ is a "native" binary that runs on the build host.
+
+- ``linux-libc-headers``: Headers needed for the cross-compiler.
+
+- ``glibc-initial``: An initial version of the Embedded GLIBC needed to
+ bootstrap ``nativesdk-glibc``.
+
+- ``nativesdk-glibc``: The Embedded GLIBC needed to bootstrap the
+ ``gcc-crosssdk``.
+
+- ``gcc-crosssdk``: The final stage of the bootstrap process for the
+ relocatable cross-compiler. The ``gcc-crosssdk`` is a transitory
+ compiler and never leaves the build host. Its purpose is to help in
+ the bootstrap process to create the eventual ``gcc-cross-canadian``
+ compiler, which is relocatable. This tool is also a "native" package
+ (i.e. it is designed to run on the build host).
+
+- ``gcc-cross-canadian``: The final relocatable cross-compiler. When
+ run on the :term:`SDKMACHINE`,
+ this tool produces executable code that runs on the target device.
+ Only one cross-canadian compiler is produced per architecture since
+ they can be targeted at different processor optimizations using
+ configurations passed to the compiler through the compile commands.
+ This circumvents the need for multiple compilers and thus reduces the
+ size of the toolchains.
+
+.. note::
+
+ For information on advantages gained when building a
+ cross-development toolchain installer, see the
+ ":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`" appendix
+ in the Yocto Project Application Development and the
+ Extensible Software Development Kit (eSDK) manual.
+
+Shared State Cache
+==================
+
+By design, the OpenEmbedded build system builds everything from scratch
+unless :term:`BitBake` can determine
+that parts do not need to be rebuilt. Fundamentally, building from
+scratch is attractive as it means all parts are built fresh and no
+possibility of stale data exists that can cause problems. When
+developers hit problems, they typically default back to building from
+scratch so they have a know state from the start.
+
+Building an image from scratch is both an advantage and a disadvantage
+to the process. As mentioned in the previous paragraph, building from
+scratch ensures that everything is current and starts from a known
+state. However, building from scratch also takes much longer as it
+generally means rebuilding things that do not necessarily need to be
+rebuilt.
+
+The Yocto Project implements shared state code that supports incremental
+builds. The implementation of the shared state code answers the
+following questions that were fundamental roadblocks within the
+OpenEmbedded incremental build support system:
+
+- What pieces of the system have changed and what pieces have not
+ changed?
+
+- How are changed pieces of software removed and replaced?
+
+- How are pre-built components that do not need to be rebuilt from
+ scratch used when they are available?
+
+For the first question, the build system detects changes in the "inputs"
+to a given task by creating a checksum (or signature) of the task's
+inputs. If the checksum changes, the system assumes the inputs have
+changed and the task needs to be rerun. For the second question, the
+shared state (sstate) code tracks which tasks add which output to the
+build process. This means the output from a given task can be removed,
+upgraded or otherwise manipulated. The third question is partly
+addressed by the solution for the second question assuming the build
+system can fetch the sstate objects from remote locations and install
+them if they are deemed to be valid.
+
+.. note::
+
+ - The build system does not maintain
+ :term:`PR` information as part of
+ the shared state packages. Consequently, considerations exist that
+ affect maintaining shared state feeds. For information on how the
+ build system works with packages and can track incrementing ``PR``
+ information, see the ":ref:`dev-manual/dev-manual-common-tasks:automatically incrementing a package version number`"
+ section in the Yocto Project Development Tasks Manual.
+
+ - The code in the build system that supports incremental builds is
+ not simple code. For techniques that help you work around issues
+ related to shared state code, see the
+ ":ref:`dev-manual/dev-manual-common-tasks:viewing metadata used to create the input signature of a shared state task`"
+ and
+ ":ref:`dev-manual/dev-manual-common-tasks:invalidating shared state to force a task to run`"
+ sections both in the Yocto Project Development Tasks Manual.
+
+The rest of this section goes into detail about the overall incremental
+build architecture, the checksums (signatures), and shared state.
+
+.. _concepts-overall-architecture:
+
+Overall Architecture
+--------------------
+
+When determining what parts of the system need to be built, BitBake
+works on a per-task basis rather than a per-recipe basis. You might
+wonder why using a per-task basis is preferred over a per-recipe basis.
+To help explain, consider having the IPK packaging backend enabled and
+then switching to DEB. In this case, the
+:ref:`ref-tasks-install` and
+:ref:`ref-tasks-package` task outputs
+are still valid. However, with a per-recipe approach, the build would
+not include the ``.deb`` files. Consequently, you would have to
+invalidate the whole build and rerun it. Rerunning everything is not the
+best solution. Also, in this case, the core must be "taught" much about
+specific tasks. This methodology does not scale well and does not allow
+users to easily add new tasks in layers or as external recipes without
+touching the packaged-staging core.
+
+.. _overview-checksums:
+
+Checksums (Signatures)
+----------------------
+
+The shared state code uses a checksum, which is a unique signature of a
+task's inputs, to determine if a task needs to be run again. Because it
+is a change in a task's inputs that triggers a rerun, the process needs
+to detect all the inputs to a given task. For shell tasks, this turns
+out to be fairly easy because the build process generates a "run" shell
+script for each task and it is possible to create a checksum that gives
+you a good idea of when the task's data changes.
+
+To complicate the problem, there are things that should not be included
+in the checksum. First, there is the actual specific build path of a
+given task - the :term:`WORKDIR`. It
+does not matter if the work directory changes because it should not
+affect the output for target packages. Also, the build process has the
+objective of making native or cross packages relocatable.
+
+.. note::
+
+ Both native and cross packages run on the
+ build host. However, cross packages generate output for the target
+ architecture.
+
+The checksum therefore needs to exclude ``WORKDIR``. The simplistic
+approach for excluding the work directory is to set ``WORKDIR`` to some
+fixed value and create the checksum for the "run" script.
+
+Another problem results from the "run" scripts containing functions that
+might or might not get called. The incremental build solution contains
+code that figures out dependencies between shell functions. This code is
+used to prune the "run" scripts down to the minimum set, thereby
+alleviating this problem and making the "run" scripts much more readable
+as a bonus.
+
+So far, solutions for shell scripts exist. What about Python tasks? The
+same approach applies even though these tasks are more difficult. The
+process needs to figure out what variables a Python function accesses
+and what functions it calls. Again, the incremental build solution
+contains code that first figures out the variable and function
+dependencies, and then creates a checksum for the data used as the input
+to the task.
+
+Like the ``WORKDIR`` case, situations exist where dependencies should be
+ignored. For these situations, you can instruct the build process to
+ignore a dependency by using a line like the following:
+::
+
+ PACKAGE_ARCHS[vardepsexclude] = "MACHINE"
+
+This example ensures that the :term:`PACKAGE_ARCHS` variable
+does not depend on the value of :term:`MACHINE`, even if it does
+reference it.
+
+Equally, there are cases where you need to add dependencies BitBake is
+not able to find. You can accomplish this by using a line like the
+following:
+::
+
+ PACKAGE_ARCHS[vardeps] = "MACHINE"
+
+This example explicitly
+adds the ``MACHINE`` variable as a dependency for ``PACKAGE_ARCHS``.
+
+As an example, consider a case with in-line Python where BitBake is not
+able to figure out dependencies. When running in debug mode (i.e. using
+``-DDD``), BitBake produces output when it discovers something for which
+it cannot figure out dependencies. The Yocto Project team has currently
+not managed to cover those dependencies in detail and is aware of the
+need to fix this situation.
+
+Thus far, this section has limited discussion to the direct inputs into
+a task. Information based on direct inputs is referred to as the
+"basehash" in the code. However, the question of a task's indirect
+inputs still exits - items already built and present in the
+:term:`Build Directory`. The checksum (or
+signature) for a particular task needs to add the hashes of all the
+tasks on which the particular task depends. Choosing which dependencies
+to add is a policy decision. However, the effect is to generate a master
+checksum that combines the basehash and the hashes of the task's
+dependencies.
+
+At the code level, a variety of ways exist by which both the basehash
+and the dependent task hashes can be influenced. Within the BitBake
+configuration file, you can give BitBake some extra information to help
+it construct the basehash. The following statement effectively results
+in a list of global variable dependency excludes (i.e. variables never
+included in any checksum):
+::
+
+ BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH DL_DIR \\
+ SSTATE_DIR THISDIR FILESEXTRAPATHS FILE_DIRNAME HOME LOGNAME SHELL TERM \\
+ USER FILESPATH STAGING_DIR_HOST STAGING_DIR_TARGET COREBASE PRSERV_HOST \\
+ PRSERV_DUMPDIR PRSERV_DUMPFILE PRSERV_LOCKDOWN PARALLEL_MAKE \\
+ CCACHE_DIR EXTERNAL_TOOLCHAIN CCACHE CCACHE_DISABLE LICENSE_PATH SDKPKGSUFFIX"
+
+The
+previous example excludes
+:term:`WORKDIR` since that variable
+is actually constructed as a path within
+:term:`TMPDIR`, which is on the
+whitelist.
+
+The rules for deciding which hashes of dependent tasks to include
+through dependency chains are more complex and are generally
+accomplished with a Python function. The code in
+``meta/lib/oe/sstatesig.py`` shows two examples of this and also
+illustrates how you can insert your own policy into the system if so
+desired. This file defines the two basic signature generators
+:term:`OpenEmbedded-Core (OE-Core)` uses: "OEBasic" and
+"OEBasicHash". By default, a dummy "noop" signature handler is enabled
+in BitBake. This means that behavior is unchanged from previous
+versions. OE-Core uses the "OEBasicHash" signature handler by default
+through this setting in the ``bitbake.conf`` file:
+::
+
+ BB_SIGNATURE_HANDLER ?= "OEBasicHash"
+
+The "OEBasicHash" ``BB_SIGNATURE_HANDLER`` is the same
+as the "OEBasic" version but adds the task hash to the `stamp
+files <#stamp-files-and-the-rerunning-of-tasks>`__. This results in any
+metadata change that changes the task hash, automatically causing the
+task to be run again. This removes the need to bump
+:term:`PR` values, and changes to metadata
+automatically ripple across the build.
+
+It is also worth noting that the end result of these signature
+generators is to make some dependency and hash information available to
+the build. This information includes:
+
+- ``BB_BASEHASH_task-``\ taskname: The base hashes for each task in the
+ recipe.
+
+- ``BB_BASEHASH_``\ filename\ ``:``\ taskname: The base hashes for each
+ dependent task.
+
+- ``BBHASHDEPS_``\ filename\ ``:``\ taskname: The task dependencies for
+ each task.
+
+- ``BB_TASKHASH``: The hash of the currently running task.
+
+Shared State
+------------
+
+Checksums and dependencies, as discussed in the previous section, solve
+half the problem of supporting a shared state. The other half of the
+problem is being able to use checksum information during the build and
+being able to reuse or rebuild specific components.
+
+The :ref:`sstate <ref-classes-sstate>` class is a
+relatively generic implementation of how to "capture" a snapshot of a
+given task. The idea is that the build process does not care about the
+source of a task's output. Output could be freshly built or it could be
+downloaded and unpacked from somewhere. In other words, the build
+process does not need to worry about its origin.
+
+Two types of output exist. One type is just about creating a directory
+in :term:`WORKDIR`. A good example is
+the output of either
+:ref:`ref-tasks-install` or
+:ref:`ref-tasks-package`. The other
+type of output occurs when a set of data is merged into a shared
+directory tree such as the sysroot.
+
+The Yocto Project team has tried to keep the details of the
+implementation hidden in ``sstate`` class. From a user's perspective,
+adding shared state wrapping to a task is as simple as this
+:ref:`ref-tasks-deploy` example taken
+from the :ref:`deploy <ref-classes-deploy>` class:
+::
+
+ DEPLOYDIR = "${WORKDIR}/deploy-${PN}"
+ SSTATETASKS += "do_deploy"
+ do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"
+ do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"
+
+ python do_deploy_setscene () {
+ sstate_setscene(d)
+ }
+ addtask do_deploy_setscene
+ do_deploy[dirs] = "${DEPLOYDIR} ${B}"
+ do_deploy[stamp-extra-info] = "${MACHINE_ARCH}"
+
+The following list explains the previous example:
+
+- Adding "do_deploy" to ``SSTATETASKS`` adds some required
+ sstate-related processing, which is implemented in the
+ :ref:`sstate <ref-classes-sstate>` class, to
+ before and after the
+ :ref:`ref-tasks-deploy` task.
+
+- The ``do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"`` declares that
+ ``do_deploy`` places its output in ``${DEPLOYDIR}`` when run normally
+ (i.e. when not using the sstate cache). This output becomes the input
+ to the shared state cache.
+
+- The ``do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"`` line
+ causes the contents of the shared state cache to be copied to
+ ``${DEPLOY_DIR_IMAGE}``.
+
+ .. note::
+
+ If ``do_deploy`` is not already in the shared state cache or if its input
+ checksum (signature) has changed from when the output was cached, the task
+ runs to populate the shared state cache, after which the contents of the
+ shared state cache is copied to ${:term:`DEPLOY_DIR_IMAGE`}. If
+ ``do_deploy`` is in the shared state cache and its signature indicates
+ that the cached output is still valid (i.e. if no relevant task inputs
+ have changed), then the contents of the shared state cache copies
+ directly to ${``DEPLOY_DIR_IMAGE``} by the ``do_deploy_setscene`` task
+ instead, skipping the ``do_deploy`` task.
+
+- The following task definition is glue logic needed to make the
+ previous settings effective:
+ ::
+
+ python do_deploy_setscene () {
+ sstate_setscene(d)
+ }
+ addtask do_deploy_setscene
+
+ ``sstate_setscene()`` takes the flags above as input and accelerates the ``do_deploy`` task
+ through the shared state cache if possible. If the task was
+ accelerated, ``sstate_setscene()`` returns True. Otherwise, it
+ returns False, and the normal ``do_deploy`` task runs. For more
+ information, see the ":ref:`setscene <bitbake:bitbake-user-manual/bitbake-user-manual-execution:setscene>`"
+ section in the BitBake User Manual.
+
+- The ``do_deploy[dirs] = "${DEPLOYDIR} ${B}"`` line creates
+ ``${DEPLOYDIR}`` and ``${B}`` before the ``do_deploy`` task runs, and
+ also sets the current working directory of ``do_deploy`` to ``${B}``.
+ For more information, see the ":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags`"
+ section in the BitBake
+ User Manual.
+
+ .. note::
+
+ In cases where ``sstate-inputdirs`` and ``sstate-outputdirs`` would be
+ the same, you can use ``sstate-plaindirs``. For example, to preserve the
+ ${:term:`PKGD`} and ${:term:`PKGDEST`} output from the ``do_package``
+ task, use the following:
+ ::
+
+ do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}"
+
+
+- The ``do_deploy[stamp-extra-info] = "${MACHINE_ARCH}"`` line appends
+ extra metadata to the `stamp
+ file <#stamp-files-and-the-rerunning-of-tasks>`__. In this case, the
+ metadata makes the task specific to a machine's architecture. See
+ ":ref:`bitbake:ref-bitbake-tasklist`"
+ section in the BitBake User Manual for more information on the
+ ``stamp-extra-info`` flag.
+
+- ``sstate-inputdirs`` and ``sstate-outputdirs`` can also be used with
+ multiple directories. For example, the following declares
+ ``PKGDESTWORK`` and ``SHLIBWORK`` as shared state input directories,
+ which populates the shared state cache, and ``PKGDATA_DIR`` and
+ ``SHLIBSDIR`` as the corresponding shared state output directories:
+ ::
+
+ do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}"
+ do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}"
+
+- These methods also include the ability to take a lockfile when
+ manipulating shared state directory structures, for cases where file
+ additions or removals are sensitive:
+ ::
+
+ do_package[sstate-lockfile] = "${PACKAGELOCK}"
+
+Behind the scenes, the shared state code works by looking in
+:term:`SSTATE_DIR` and
+:term:`SSTATE_MIRRORS` for
+shared state files. Here is an example:
+::
+
+ SSTATE_MIRRORS ?= "\
+ file://.\* http://someserver.tld/share/sstate/PATH;downloadfilename=PATH \n \
+ file://.\* file:///some/local/dir/sstate/PATH"
+
+.. note::
+
+ The shared state directory (``SSTATE_DIR``) is organized into two-character
+ subdirectories, where the subdirectory names are based on the first two
+ characters of the hash.
+ If the shared state directory structure for a mirror has the same structure
+ as ``SSTATE_DIR``, you must specify "PATH" as part of the URI to enable the build
+ system to map to the appropriate subdirectory.
+
+The shared state package validity can be detected just by looking at the
+filename since the filename contains the task checksum (or signature) as
+described earlier in this section. If a valid shared state package is
+found, the build process downloads it and uses it to accelerate the
+task.
+
+The build processes use the ``*_setscene`` tasks for the task
+acceleration phase. BitBake goes through this phase before the main
+execution code and tries to accelerate any tasks for which it can find
+shared state packages. If a shared state package for a task is
+available, the shared state package is used. This means the task and any
+tasks on which it is dependent are not executed.
+
+As a real world example, the aim is when building an IPK-based image,
+only the
+:ref:`ref-tasks-package_write_ipk`
+tasks would have their shared state packages fetched and extracted.
+Since the sysroot is not used, it would never get extracted. This is
+another reason why a task-based approach is preferred over a
+recipe-based approach, which would have to install the output from every
+task.
+
+Automatically Added Runtime Dependencies
+========================================
+
+The OpenEmbedded build system automatically adds common types of runtime
+dependencies between packages, which means that you do not need to
+explicitly declare the packages using
+:term:`RDEPENDS`. Three automatic
+mechanisms exist (``shlibdeps``, ``pcdeps``, and ``depchains``) that
+handle shared libraries, package configuration (pkg-config) modules, and
+``-dev`` and ``-dbg`` packages, respectively. For other types of runtime
+dependencies, you must manually declare the dependencies.
+
+- ``shlibdeps``: During the
+ :ref:`ref-tasks-package` task of
+ each recipe, all shared libraries installed by the recipe are
+ located. For each shared library, the package that contains the
+ shared library is registered as providing the shared library. More
+ specifically, the package is registered as providing the
+ `soname <https://en.wikipedia.org/wiki/Soname>`__ of the library. The
+ resulting shared-library-to-package mapping is saved globally in
+ :term:`PKGDATA_DIR` by the
+ :ref:`ref-tasks-packagedata`
+ task.
+
+ Simultaneously, all executables and shared libraries installed by the
+ recipe are inspected to see what shared libraries they link against.
+ For each shared library dependency that is found, ``PKGDATA_DIR`` is
+ queried to see if some package (likely from a different recipe)
+ contains the shared library. If such a package is found, a runtime
+ dependency is added from the package that depends on the shared
+ library to the package that contains the library.
+
+ The automatically added runtime dependency also includes a version
+ restriction. This version restriction specifies that at least the
+ current version of the package that provides the shared library must
+ be used, as if "package (>= version)" had been added to ``RDEPENDS``.
+ This forces an upgrade of the package containing the shared library
+ when installing the package that depends on the library, if needed.
+
+ If you want to avoid a package being registered as providing a
+ particular shared library (e.g. because the library is for internal
+ use only), then add the library to
+ :term:`PRIVATE_LIBS` inside
+ the package's recipe.
+
+- ``pcdeps``: During the ``do_package`` task of each recipe, all
+ pkg-config modules (``*.pc`` files) installed by the recipe are
+ located. For each module, the package that contains the module is
+ registered as providing the module. The resulting module-to-package
+ mapping is saved globally in ``PKGDATA_DIR`` by the
+ ``do_packagedata`` task.
+
+ Simultaneously, all pkg-config modules installed by the recipe are
+ inspected to see what other pkg-config modules they depend on. A
+ module is seen as depending on another module if it contains a
+ "Requires:" line that specifies the other module. For each module
+ dependency, ``PKGDATA_DIR`` is queried to see if some package
+ contains the module. If such a package is found, a runtime dependency
+ is added from the package that depends on the module to the package
+ that contains the module.
+
+ .. note::
+
+ The
+ pcdeps
+ mechanism most often infers dependencies between
+ -dev
+ packages.
+
+- ``depchains``: If a package ``foo`` depends on a package ``bar``,
+ then ``foo-dev`` and ``foo-dbg`` are also made to depend on
+ ``bar-dev`` and ``bar-dbg``, respectively. Taking the ``-dev``
+ packages as an example, the ``bar-dev`` package might provide headers
+ and shared library symlinks needed by ``foo-dev``, which shows the
+ need for a dependency between the packages.
+
+ The dependencies added by ``depchains`` are in the form of
+ :term:`RRECOMMENDS`.
+
+ .. note::
+
+ By default, ``foo-dev`` also has an ``RDEPENDS``-style dependency on
+ ``foo``, because the default value of ``RDEPENDS_${PN}-dev`` (set in
+ bitbake.conf) includes "${PN}".
+
+ To ensure that the dependency chain is never broken, ``-dev`` and
+ ``-dbg`` packages are always generated by default, even if the
+ packages turn out to be empty. See the
+ :term:`ALLOW_EMPTY` variable
+ for more information.
+
+The ``do_package`` task depends on the ``do_packagedata`` task of each
+recipe in :term:`DEPENDS` through use
+of a ``[``\ :ref:`deptask <bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags>`\ ``]``
+declaration, which guarantees that the required
+shared-library/module-to-package mapping information will be available
+when needed as long as ``DEPENDS`` has been correctly set.
+
+Fakeroot and Pseudo
+===================
+
+Some tasks are easier to implement when allowed to perform certain
+operations that are normally reserved for the root user (e.g.
+:ref:`ref-tasks-install`,
+:ref:`do_package_write* <ref-tasks-package_write_deb>`,
+:ref:`ref-tasks-rootfs`, and
+:ref:`do_image* <ref-tasks-image>`). For example,
+the ``do_install`` task benefits from being able to set the UID and GID
+of installed files to arbitrary values.
+
+One approach to allowing tasks to perform root-only operations would be
+to require :term:`BitBake` to run as
+root. However, this method is cumbersome and has security issues. The
+approach that is actually used is to run tasks that benefit from root
+privileges in a "fake" root environment. Within this environment, the
+task and its child processes believe that they are running as the root
+user, and see an internally consistent view of the filesystem. As long
+as generating the final output (e.g. a package or an image) does not
+require root privileges, the fact that some earlier steps ran in a fake
+root environment does not cause problems.
+
+The capability to run tasks in a fake root environment is known as
+"`fakeroot <http://man.he.net/man1/fakeroot>`__", which is derived from
+the BitBake keyword/variable flag that requests a fake root environment
+for a task.
+
+In the :term:`OpenEmbedded Build System`,
+the program that
+implements fakeroot is known as
+`Pseudo <https://www.yoctoproject.org/software-item/pseudo/>`__. Pseudo
+overrides system calls by using the environment variable ``LD_PRELOAD``,
+which results in the illusion of running as root. To keep track of
+"fake" file ownership and permissions resulting from operations that
+require root permissions, Pseudo uses an SQLite 3 database. This
+database is stored in
+``${``\ :term:`WORKDIR`\ ``}/pseudo/files.db``
+for individual recipes. Storing the database in a file as opposed to in
+memory gives persistence between tasks and builds, which is not
+accomplished using fakeroot.
+
+.. note::
+
+ If you add your own task that manipulates the same files or
+ directories as a fakeroot task, then that task also needs to run
+ under fakeroot. Otherwise, the task cannot run root-only operations,
+ and cannot see the fake file ownership and permissions set by the
+ other task. You need to also add a dependency on
+ virtual/fakeroot-native:do_populate_sysroot
+ , giving the following:
+ ::
+
+ fakeroot do_mytask () {
+ ...
+ }
+ do_mytask[depends] += "virtual/fakeroot-native:do_populate_sysroot"
+
+
+For more information, see the
+:term:`FAKEROOT* <bitbake:FAKEROOT>` variables in the
+BitBake User Manual. You can also reference the "`Why Not
+Fakeroot? <https://github.com/wrpseudo/pseudo/wiki/WhyNotFakeroot>`__"
+article for background information on Fakeroot and Pseudo.
diff --git a/poky/documentation/overview-manual/overview-manual-development-environment.rst b/poky/documentation/overview-manual/overview-manual-development-environment.rst
new file mode 100644
index 0000000..3b5147d
--- /dev/null
+++ b/poky/documentation/overview-manual/overview-manual-development-environment.rst
@@ -0,0 +1,672 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*****************************************
+The Yocto Project Development Environment
+*****************************************
+
+This chapter takes a look at the Yocto Project development environment.
+The chapter provides Yocto Project Development environment concepts that
+help you understand how work is accomplished in an open source
+environment, which is very different as compared to work accomplished in
+a closed, proprietary environment.
+
+Specifically, this chapter addresses open source philosophy, source
+repositories, workflows, Git, and licensing.
+
+Open Source Philosophy
+======================
+
+Open source philosophy is characterized by software development directed
+by peer production and collaboration through an active community of
+developers. Contrast this to the more standard centralized development
+models used by commercial software companies where a finite set of
+developers produces a product for sale using a defined set of procedures
+that ultimately result in an end product whose architecture and source
+material are closed to the public.
+
+Open source projects conceptually have differing concurrent agendas,
+approaches, and production. These facets of the development process can
+come from anyone in the public (community) who has a stake in the
+software project. The open source environment contains new copyright,
+licensing, domain, and consumer issues that differ from the more
+traditional development environment. In an open source environment, the
+end product, source material, and documentation are all available to the
+public at no cost.
+
+A benchmark example of an open source project is the Linux kernel, which
+was initially conceived and created by Finnish computer science student
+Linus Torvalds in 1991. Conversely, a good example of a non-open source
+project is the Windows family of operating systems developed by
+Microsoft Corporation.
+
+Wikipedia has a good historical description of the Open Source
+Philosophy `here <http://en.wikipedia.org/wiki/Open_source>`__. You can
+also find helpful information on how to participate in the Linux
+Community
+`here <http://ldn.linuxfoundation.org/book/how-participate-linux-community>`__.
+
+.. _gs-the-development-host:
+
+The Development Host
+====================
+
+A development host or :term:`Build Host` is key to
+using the Yocto Project. Because the goal of the Yocto Project is to
+develop images or applications that run on embedded hardware,
+development of those images and applications generally takes place on a
+system not intended to run the software - the development host.
+
+You need to set up a development host in order to use it with the Yocto
+Project. Most find that it is best to have a native Linux machine
+function as the development host. However, it is possible to use a
+system that does not run Linux as its operating system as your
+development host. When you have a Mac or Windows-based system, you can
+set it up as the development host by using
+`CROPS <https://github.com/crops/poky-container>`__, which leverages
+`Docker Containers <https://www.docker.com/>`__. Once you take the steps
+to set up a CROPS machine, you effectively have access to a shell
+environment that is similar to what you see when using a Linux-based
+development host. For the steps needed to set up a system using CROPS,
+see the
+":ref:`dev-manual/dev-manual-start:setting up to use cross platforms (crops)`"
+section in
+the Yocto Project Development Tasks Manual.
+
+If your development host is going to be a system that runs a Linux
+distribution, steps still exist that you must take to prepare the system
+for use with the Yocto Project. You need to be sure that the Linux
+distribution on the system is one that supports the Yocto Project. You
+also need to be sure that the correct set of host packages are installed
+that allow development using the Yocto Project. For the steps needed to
+set up a development host that runs Linux, see the
+":ref:`dev-manual/dev-manual-start:setting up a native linux host`"
+section in the Yocto Project Development Tasks Manual.
+
+Once your development host is set up to use the Yocto Project, several
+methods exist for you to do work in the Yocto Project environment:
+
+- *Command Lines, BitBake, and Shells:* Traditional development in the
+ Yocto Project involves using the :term:`OpenEmbedded Build System`,
+ which uses
+ BitBake, in a command-line environment from a shell on your
+ development host. You can accomplish this from a host that is a
+ native Linux machine or from a host that has been set up with CROPS.
+ Either way, you create, modify, and build images and applications all
+ within a shell-based environment using components and tools available
+ through your Linux distribution and the Yocto Project.
+
+ For a general flow of the build procedures, see the
+ ":ref:`dev-manual/dev-manual-common-tasks:building a simple image`"
+ section in the Yocto Project Development Tasks Manual.
+
+- *Board Support Package (BSP) Development:* Development of BSPs
+ involves using the Yocto Project to create and test layers that allow
+ easy development of images and applications targeted for specific
+ hardware. To development BSPs, you need to take some additional steps
+ beyond what was described in setting up a development host.
+
+ The :doc:`../bsp-guide/bsp-guide` provides BSP-related development
+ information. For specifics on development host preparation, see the
+ ":ref:`bsp-guide/bsp:preparing your build host to work with bsp layers`"
+ section in the Yocto Project Board Support Package (BSP) Developer's
+ Guide.
+
+- *Kernel Development:* If you are going to be developing kernels using
+ the Yocto Project you likely will be using ``devtool``. A workflow
+ using ``devtool`` makes kernel development quicker by reducing
+ iteration cycle times.
+
+ The :doc:`../kernel-dev/kernel-dev` provides kernel-related
+ development information. For specifics on development host
+ preparation, see the
+ ":ref:`kernel-dev/kernel-dev-common:preparing the build host to work on the kernel`"
+ section in the Yocto Project Linux Kernel Development Manual.
+
+- *Using Toaster:* The other Yocto Project development method that
+ involves an interface that effectively puts the Yocto Project into
+ the background is Toaster. Toaster provides an interface to the
+ OpenEmbedded build system. The interface enables you to configure and
+ run your builds. Information about builds is collected and stored in
+ a database. You can use Toaster to configure and start builds on
+ multiple remote build servers.
+
+ For steps that show you how to set up your development host to use
+ Toaster and on how to use Toaster in general, see the
+ :doc:`../toaster-manual/toaster-manual`.
+
+.. _yocto-project-repositories:
+
+Yocto Project Source Repositories
+=================================
+
+The Yocto Project team maintains complete source repositories for all
+Yocto Project files at :yocto_git:`/`. This web-based source
+code browser is organized into categories by function such as IDE
+Plugins, Matchbox, Poky, Yocto Linux Kernel, and so forth. From the
+interface, you can click on any particular item in the "Name" column and
+see the URL at the bottom of the page that you need to clone a Git
+repository for that particular item. Having a local Git repository of
+the :term:`Source Directory`, which
+is usually named "poky", allows you to make changes, contribute to the
+history, and ultimately enhance the Yocto Project's tools, Board Support
+Packages, and so forth.
+
+For any supported release of Yocto Project, you can also go to the
+:yocto_home:`Yocto Project Website <>` and select the "DOWNLOADS"
+item from the "SOFTWARE" menu and get a released tarball of the ``poky``
+repository, any supported BSP tarball, or Yocto Project tools. Unpacking
+these tarballs gives you a snapshot of the released files.
+
+.. note::
+
+ - The recommended method for setting up the Yocto Project
+ :term:`Source Directory` and the files
+ for supported BSPs (e.g., ``meta-intel``) is to use `Git <#git>`__
+ to create a local copy of the upstream repositories.
+
+ - Be sure to always work in matching branches for both the selected
+ BSP repository and the Source Directory (i.e. ``poky``)
+ repository. For example, if you have checked out the "master"
+ branch of ``poky`` and you are going to use ``meta-intel``, be
+ sure to checkout the "master" branch of ``meta-intel``.
+
+In summary, here is where you can get the project files needed for
+development:
+
+- :yocto_git:`Source Repositories: <>` This area contains IDE
+ Plugins, Matchbox, Poky, Poky Support, Tools, Yocto Linux Kernel, and
+ Yocto Metadata Layers. You can create local copies of Git
+ repositories for each of these areas.
+
+ .. image:: figures/source-repos.png
+ :align: center
+
+ For steps on how to view and access these upstream Git repositories,
+ see the ":ref:`dev-manual/dev-manual-start:accessing source repositories`"
+ Section in the Yocto Project Development Tasks Manual.
+
+- :yocto_dl:`Index of /releases: <releases>` This is an index
+ of releases such as Poky, Pseudo, installers for cross-development
+ toolchains, miscellaneous support and all released versions of Yocto
+ Project in the form of images or tarballs. Downloading and extracting
+ these files does not produce a local copy of the Git repository but
+ rather a snapshot of a particular release or image.
+
+ .. image:: figures/index-downloads.png
+ :align: center
+
+ For steps on how to view and access these files, see the
+ ":ref:`dev-manual/dev-manual-start:accessing index of releases`"
+ section in the Yocto Project Development Tasks Manual.
+
+- *"DOWNLOADS" page for the* :yocto_home:`Yocto Project Website <>` *:*
+
+ The Yocto Project website includes a "DOWNLOADS" page accessible
+ through the "SOFTWARE" menu that allows you to download any Yocto
+ Project release, tool, and Board Support Package (BSP) in tarball
+ form. The tarballs are similar to those found in the
+ :yocto_dl:`Index of /releases: <releases>` area.
+
+ .. image:: figures/yp-download.png
+ :align: center
+
+ For steps on how to use the "DOWNLOADS" page, see the
+ ":ref:`dev-manual/dev-manual-start:using the downloads page`"
+ section in the Yocto Project Development Tasks Manual.
+
+.. _gs-git-workflows-and-the-yocto-project:
+
+Git Workflows and the Yocto Project
+===================================
+
+Developing using the Yocto Project likely requires the use of
+`Git <#git>`__. Git is a free, open source distributed version control
+system used as part of many collaborative design environments. This
+section provides workflow concepts using the Yocto Project and Git. In
+particular, the information covers basic practices that describe roles
+and actions in a collaborative development environment.
+
+.. note::
+
+ If you are familiar with this type of development environment, you
+ might not want to read this section.
+
+The Yocto Project files are maintained using Git in "branches" whose Git
+histories track every change and whose structures provide branches for
+all diverging functionality. Although there is no need to use Git, many
+open source projects do so.
+
+For the Yocto Project, a key individual called the "maintainer" is
+responsible for the integrity of the "master" branch of a given Git
+repository. The "master" branch is the "upstream" repository from which
+final or most recent builds of a project occur. The maintainer is
+responsible for accepting changes from other developers and for
+organizing the underlying branch structure to reflect release strategies
+and so forth.
+
+.. note::
+
+ For information on finding out who is responsible for (maintains) a
+ particular area of code in the Yocto Project, see the
+ ":ref:`dev-manual/dev-manual-common-tasks:submitting a change to the yocto project`"
+ section of the Yocto Project Development Tasks Manual.
+
+The Yocto Project ``poky`` Git repository also has an upstream
+contribution Git repository named ``poky-contrib``. You can see all the
+branches in this repository using the web interface of the
+:yocto_git:`Source Repositories <>` organized within the "Poky Support"
+area. These branches hold changes (commits) to the project that have
+been submitted or committed by the Yocto Project development team and by
+community members who contribute to the project. The maintainer
+determines if the changes are qualified to be moved from the "contrib"
+branches into the "master" branch of the Git repository.
+
+Developers (including contributing community members) create and
+maintain cloned repositories of upstream branches. The cloned
+repositories are local to their development platforms and are used to
+develop changes. When a developer is satisfied with a particular feature
+or change, they "push" the change to the appropriate "contrib"
+repository.
+
+Developers are responsible for keeping their local repository up-to-date
+with whatever upstream branch they are working against. They are also
+responsible for straightening out any conflicts that might arise within
+files that are being worked on simultaneously by more than one person.
+All this work is done locally on the development host before anything is
+pushed to a "contrib" area and examined at the maintainer's level.
+
+A somewhat formal method exists by which developers commit changes and
+push them into the "contrib" area and subsequently request that the
+maintainer include them into an upstream branch. This process is called
+"submitting a patch" or "submitting a change." For information on
+submitting patches and changes, see the
+":ref:`dev-manual/dev-manual-common-tasks:submitting a change to the yocto project`"
+section in the Yocto Project Development Tasks Manual.
+
+In summary, a single point of entry exists for changes into a "master"
+or development branch of the Git repository, which is controlled by the
+project's maintainer. And, a set of developers exist who independently
+develop, test, and submit changes to "contrib" areas for the maintainer
+to examine. The maintainer then chooses which changes are going to
+become a permanent part of the project.
+
+.. image:: figures/git-workflow.png
+ :align: center
+
+While each development environment is unique, there are some best
+practices or methods that help development run smoothly. The following
+list describes some of these practices. For more information about Git
+workflows, see the workflow topics in the `Git Community
+Book <http://book.git-scm.com>`__.
+
+- *Make Small Changes:* It is best to keep the changes you commit small
+ as compared to bundling many disparate changes into a single commit.
+ This practice not only keeps things manageable but also allows the
+ maintainer to more easily include or refuse changes.
+
+- *Make Complete Changes:* It is also good practice to leave the
+ repository in a state that allows you to still successfully build
+ your project. In other words, do not commit half of a feature, then
+ add the other half as a separate, later commit. Each commit should
+ take you from one buildable project state to another buildable state.
+
+- *Use Branches Liberally:* It is very easy to create, use, and delete
+ local branches in your working Git repository on the development
+ host. You can name these branches anything you like. It is helpful to
+ give them names associated with the particular feature or change on
+ which you are working. Once you are done with a feature or change and
+ have merged it into your local master branch, simply discard the
+ temporary branch.
+
+- *Merge Changes:* The ``git merge`` command allows you to take the
+ changes from one branch and fold them into another branch. This
+ process is especially helpful when more than a single developer might
+ be working on different parts of the same feature. Merging changes
+ also automatically identifies any collisions or "conflicts" that
+ might happen as a result of the same lines of code being altered by
+ two different developers.
+
+- *Manage Branches:* Because branches are easy to use, you should use a
+ system where branches indicate varying levels of code readiness. For
+ example, you can have a "work" branch to develop in, a "test" branch
+ where the code or change is tested, a "stage" branch where changes
+ are ready to be committed, and so forth. As your project develops,
+ you can merge code across the branches to reflect ever-increasing
+ stable states of the development.
+
+- *Use Push and Pull:* The push-pull workflow is based on the concept
+ of developers "pushing" local commits to a remote repository, which
+ is usually a contribution repository. This workflow is also based on
+ developers "pulling" known states of the project down into their
+ local development repositories. The workflow easily allows you to
+ pull changes submitted by other developers from the upstream
+ repository into your work area ensuring that you have the most recent
+ software on which to develop. The Yocto Project has two scripts named
+ ``create-pull-request`` and ``send-pull-request`` that ship with the
+ release to facilitate this workflow. You can find these scripts in
+ the ``scripts`` folder of the
+ :term:`Source Directory`. For information
+ on how to use these scripts, see the
+ ":ref:`dev-manual/dev-manual-common-tasks:using scripts to push a change upstream and request a pull`"
+ section in the Yocto Project Development Tasks Manual.
+
+- *Patch Workflow:* This workflow allows you to notify the maintainer
+ through an email that you have a change (or patch) you would like
+ considered for the "master" branch of the Git repository. To send
+ this type of change, you format the patch and then send the email
+ using the Git commands ``git format-patch`` and ``git send-email``.
+ For information on how to use these scripts, see the
+ ":ref:`dev-manual/dev-manual-common-tasks:submitting a change to the yocto project`"
+ section in the Yocto Project Development Tasks Manual.
+
+Git
+===
+
+The Yocto Project makes extensive use of Git, which is a free, open
+source distributed version control system. Git supports distributed
+development, non-linear development, and can handle large projects. It
+is best that you have some fundamental understanding of how Git tracks
+projects and how to work with Git if you are going to use the Yocto
+Project for development. This section provides a quick overview of how
+Git works and provides you with a summary of some essential Git
+commands.
+
+.. note::
+
+ - For more information on Git, see
+ http://git-scm.com/documentation.
+
+ - If you need to download Git, it is recommended that you add Git to
+ your system through your distribution's "software store" (e.g. for
+ Ubuntu, use the Ubuntu Software feature). For the Git download
+ page, see http://git-scm.com/download.
+
+ - For information beyond the introductory nature in this section,
+ see the ":ref:`dev-manual/dev-manual-start:locating yocto project source files`"
+ section in the Yocto Project Development Tasks Manual.
+
+Repositories, Tags, and Branches
+--------------------------------
+
+As mentioned briefly in the previous section and also in the "`Git
+Workflows and the Yocto
+Project <#gs-git-workflows-and-the-yocto-project>`__" section, the Yocto
+Project maintains source repositories at :yocto_git:`/`. If you
+look at this web-interface of the repositories, each item is a separate
+Git repository.
+
+Git repositories use branching techniques that track content change (not
+files) within a project (e.g. a new feature or updated documentation).
+Creating a tree-like structure based on project divergence allows for
+excellent historical information over the life of a project. This
+methodology also allows for an environment from which you can do lots of
+local experimentation on projects as you develop changes or new
+features.
+
+A Git repository represents all development efforts for a given project.
+For example, the Git repository ``poky`` contains all changes and
+developments for that repository over the course of its entire life.
+That means that all changes that make up all releases are captured. The
+repository maintains a complete history of changes.
+
+You can create a local copy of any repository by "cloning" it with the
+``git clone`` command. When you clone a Git repository, you end up with
+an identical copy of the repository on your development system. Once you
+have a local copy of a repository, you can take steps to develop
+locally. For examples on how to clone Git repositories, see the
+":ref:`dev-manual/dev-manual-start:locating yocto project source files`"
+section in the Yocto Project Development Tasks Manual.
+
+It is important to understand that Git tracks content change and not
+files. Git uses "branches" to organize different development efforts.
+For example, the ``poky`` repository has several branches that include
+the current "&DISTRO_NAME_NO_CAP;" branch, the "master" branch, and many
+branches for past Yocto Project releases. You can see all the branches
+by going to https://git.yoctoproject.org/cgit.cgi/poky/ and clicking on the
+``[...]`` link beneath the "Branch" heading.
+
+Each of these branches represents a specific area of development. The
+"master" branch represents the current or most recent development. All
+other branches represent offshoots of the "master" branch.
+
+When you create a local copy of a Git repository, the copy has the same
+set of branches as the original. This means you can use Git to create a
+local working area (also called a branch) that tracks a specific
+development branch from the upstream source Git repository. in other
+words, you can define your local Git environment to work on any
+development branch in the repository. To help illustrate, consider the
+following example Git commands:
+::
+
+ $ cd ~
+ $ git clone git://git.yoctoproject.org/poky
+ $ cd poky
+ $ git checkout -b &DISTRO_NAME_NO_CAP; origin/&DISTRO_NAME_NO_CAP;
+
+In the previous example
+after moving to the home directory, the ``git clone`` command creates a
+local copy of the upstream ``poky`` Git repository. By default, Git
+checks out the "master" branch for your work. After changing the working
+directory to the new local repository (i.e. ``poky``), the
+``git checkout`` command creates and checks out a local branch named
+"&DISTRO_NAME_NO_CAP;", which tracks the upstream
+"origin/&DISTRO_NAME_NO_CAP;" branch. Changes you make while in this
+branch would ultimately affect the upstream "&DISTRO_NAME_NO_CAP;" branch
+of the ``poky`` repository.
+
+It is important to understand that when you create and checkout a local
+working branch based on a branch name, your local environment matches
+the "tip" of that particular development branch at the time you created
+your local branch, which could be different from the files in the
+"master" branch of the upstream repository. In other words, creating and
+checking out a local branch based on the "&DISTRO_NAME_NO_CAP;" branch
+name is not the same as checking out the "master" branch in the
+repository. Keep reading to see how you create a local snapshot of a
+Yocto Project Release.
+
+Git uses "tags" to mark specific changes in a repository branch
+structure. Typically, a tag is used to mark a special point such as the
+final change (or commit) before a project is released. You can see the
+tags used with the ``poky`` Git repository by going to
+https://git.yoctoproject.org/cgit.cgi/poky/ and clicking on the ``[...]`` link
+beneath the "Tag" heading.
+
+Some key tags for the ``poky`` repository are ``jethro-14.0.3``,
+``morty-16.0.1``, ``pyro-17.0.0``, and
+``&DISTRO_NAME_NO_CAP;-&POKYVERSION;``. These tags represent Yocto Project
+releases.
+
+When you create a local copy of the Git repository, you also have access
+to all the tags in the upstream repository. Similar to branches, you can
+create and checkout a local working Git branch based on a tag name. When
+you do this, you get a snapshot of the Git repository that reflects the
+state of the files when the change was made associated with that tag.
+The most common use is to checkout a working branch that matches a
+specific Yocto Project release. Here is an example:
+::
+
+ $ cd ~
+ $ git clone git://git.yoctoproject.org/poky
+ $ cd poky
+ $ git fetch --tags
+ $ git checkout tags/rocko-18.0.0 -b my_rocko-18.0.0
+
+In this example, the name
+of the top-level directory of your local Yocto Project repository is
+``poky``. After moving to the ``poky`` directory, the ``git fetch``
+command makes all the upstream tags available locally in your
+repository. Finally, the ``git checkout`` command creates and checks out
+a branch named "my-rocko-18.0.0" that is based on the upstream branch
+whose "HEAD" matches the commit in the repository associated with the
+"rocko-18.0.0" tag. The files in your repository now exactly match that
+particular Yocto Project release as it is tagged in the upstream Git
+repository. It is important to understand that when you create and
+checkout a local working branch based on a tag, your environment matches
+a specific point in time and not the entire development branch (i.e.
+from the "tip" of the branch backwards).
+
+Basic Commands
+--------------
+
+Git has an extensive set of commands that lets you manage changes and
+perform collaboration over the life of a project. Conveniently though,
+you can manage with a small set of basic operations and workflows once
+you understand the basic philosophy behind Git. You do not have to be an
+expert in Git to be functional. A good place to look for instruction on
+a minimal set of Git commands is
+`here <http://git-scm.com/documentation>`__.
+
+The following list of Git commands briefly describes some basic Git
+operations as a way to get started. As with any set of commands, this
+list (in most cases) simply shows the base command and omits the many
+arguments it supports. See the Git documentation for complete
+descriptions and strategies on how to use these commands:
+
+- *git init:* Initializes an empty Git repository. You cannot use
+ Git commands unless you have a ``.git`` repository.
+
+- *git clone:* Creates a local clone of a Git repository that is on
+ equal footing with a fellow developer's Git repository or an upstream
+ repository.
+
+- *git add:* Locally stages updated file contents to the index that
+ Git uses to track changes. You must stage all files that have changed
+ before you can commit them.
+
+- *git commit:* Creates a local "commit" that documents the changes
+ you made. Only changes that have been staged can be committed.
+ Commits are used for historical purposes, for determining if a
+ maintainer of a project will allow the change, and for ultimately
+ pushing the change from your local Git repository into the project's
+ upstream repository.
+
+- *git status:* Reports any modified files that possibly need to be
+ staged and gives you a status of where you stand regarding local
+ commits as compared to the upstream repository.
+
+- *git checkout branch-name:* Changes your local working branch and
+ in this form assumes the local branch already exists. This command is
+ analogous to "cd".
+
+- *git checkout –b working-branch upstream-branch:* Creates and
+ checks out a working branch on your local machine. The local branch
+ tracks the upstream branch. You can use your local branch to isolate
+ your work. It is a good idea to use local branches when adding
+ specific features or changes. Using isolated branches facilitates
+ easy removal of changes if they do not work out.
+
+- *git branch:* Displays the existing local branches associated
+ with your local repository. The branch that you have currently
+ checked out is noted with an asterisk character.
+
+- *git branch -D branch-name:* Deletes an existing local branch.
+ You need to be in a local branch other than the one you are deleting
+ in order to delete branch-name.
+
+- *git pull --rebase:* Retrieves information from an upstream Git
+ repository and places it in your local Git repository. You use this
+ command to make sure you are synchronized with the repository from
+ which you are basing changes (.e.g. the "master" branch). The
+ "--rebase" option ensures that any local commits you have in your
+ branch are preserved at the top of your local branch.
+
+- *git push repo-name local-branch:upstream-branch:* Sends
+ all your committed local changes to the upstream Git repository that
+ your local repository is tracking (e.g. a contribution repository).
+ The maintainer of the project draws from these repositories to merge
+ changes (commits) into the appropriate branch of project's upstream
+ repository.
+
+- *git merge:* Combines or adds changes from one local branch of
+ your repository with another branch. When you create a local Git
+ repository, the default branch is named "master". A typical workflow
+ is to create a temporary branch that is based off "master" that you
+ would use for isolated work. You would make your changes in that
+ isolated branch, stage and commit them locally, switch to the
+ "master" branch, and then use the ``git merge`` command to apply the
+ changes from your isolated branch into the currently checked out
+ branch (e.g. "master"). After the merge is complete and if you are
+ done with working in that isolated branch, you can safely delete the
+ isolated branch.
+
+- *git cherry-pick commits:* Choose and apply specific commits from
+ one branch into another branch. There are times when you might not be
+ able to merge all the changes in one branch with another but need to
+ pick out certain ones.
+
+- *gitk:* Provides a GUI view of the branches and changes in your
+ local Git repository. This command is a good way to graphically see
+ where things have diverged in your local repository.
+
+ .. note::
+
+ You need to install the
+ gitk
+ package on your development system to use this command.
+
+- *git log:* Reports a history of your commits to the repository.
+ This report lists all commits regardless of whether you have pushed
+ them upstream or not.
+
+- *git diff:* Displays line-by-line differences between a local
+ working file and the same file as understood by Git. This command is
+ useful to see what you have changed in any given file.
+
+Licensing
+=========
+
+Because open source projects are open to the public, they have different
+licensing structures in place. License evolution for both Open Source
+and Free Software has an interesting history. If you are interested in
+this history, you can find basic information here:
+
+- `Open source license
+ history <http://en.wikipedia.org/wiki/Open-source_license>`__
+
+- `Free software license
+ history <http://en.wikipedia.org/wiki/Free_software_license>`__
+
+In general, the Yocto Project is broadly licensed under the
+Massachusetts Institute of Technology (MIT) License. MIT licensing
+permits the reuse of software within proprietary software as long as the
+license is distributed with that software. MIT is also compatible with
+the GNU General Public License (GPL). Patches to the Yocto Project
+follow the upstream licensing scheme. You can find information on the
+MIT license
+`here <http://www.opensource.org/licenses/mit-license.php>`__. You can
+find information on the GNU GPL
+`here <http://www.opensource.org/licenses/LGPL-3.0>`__.
+
+When you build an image using the Yocto Project, the build process uses
+a known list of licenses to ensure compliance. You can find this list in
+the :term:`Source Directory` at
+``meta/files/common-licenses``. Once the build completes, the list of
+all licenses found and used during that build are kept in the
+:term:`Build Directory` at
+``tmp/deploy/licenses``.
+
+If a module requires a license that is not in the base list, the build
+process generates a warning during the build. These tools make it easier
+for a developer to be certain of the licenses with which their shipped
+products must comply. However, even with these tools it is still up to
+the developer to resolve potential licensing issues.
+
+The base list of licenses used by the build process is a combination of
+the Software Package Data Exchange (SPDX) list and the Open Source
+Initiative (OSI) projects. `SPDX Group <http://spdx.org>`__ is a working
+group of the Linux Foundation that maintains a specification for a
+standard format for communicating the components, licenses, and
+copyrights associated with a software package.
+`OSI <http://opensource.org>`__ is a corporation dedicated to the Open
+Source Definition and the effort for reviewing and approving licenses
+that conform to the Open Source Definition (OSD).
+
+You can find a list of the combined SPDX and OSI licenses that the Yocto
+Project uses in the ``meta/files/common-licenses`` directory in your
+:term:`Source Directory`.
+
+For information that can help you maintain compliance with various open
+source licensing during the lifecycle of a product created using the
+Yocto Project, see the
+":ref:`dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle`"
+section in the Yocto Project Development Tasks Manual.
diff --git a/poky/documentation/overview-manual/overview-manual-development-environment.xml b/poky/documentation/overview-manual/overview-manual-development-environment.xml
index 8415d1d..08ad071 100644
--- a/poky/documentation/overview-manual/overview-manual-development-environment.xml
+++ b/poky/documentation/overview-manual/overview-manual-development-environment.xml
@@ -327,7 +327,7 @@
For the Yocto Project, a key individual called the "maintainer" is
responsible for the integrity of the "master" branch of a given Git
repository.
- The "master" branch is the “upstream” repository from which final or
+ The "master" branch is the "upstream" repository from which final or
most recent builds of a project occur.
The maintainer is responsible for accepting changes from other
developers and for organizing the underlying branch structure to
@@ -372,7 +372,7 @@
might arise within files that are being worked on simultaneously by
more than one person.
All this work is done locally on the development host before
- anything is pushed to a "contrib" area and examined at the maintainer’s
+ anything is pushed to a "contrib" area and examined at the maintainer's
level.
</para>
@@ -380,7 +380,7 @@
A somewhat formal method exists by which developers commit changes
and push them into the "contrib" area and subsequently request that
the maintainer include them into an upstream branch.
- This process is called “submitting a patch” or "submitting a change."
+ This process is called "submitting a patch" or "submitting a change."
For information on submitting patches and changes, see the
"<ulink url='&YOCTO_DOCS_DEV_URL;#how-to-submit-a-change'>Submitting a Change to the Yocto Project</ulink>"
section in the Yocto Project Development Tasks Manual.
@@ -389,7 +389,7 @@
<para>
In summary, a single point of entry
exists for changes into a "master" or development branch of the
- Git repository, which is controlled by the project’s maintainer.
+ Git repository, which is controlled by the project's maintainer.
And, a set of developers exist who independently develop, test, and
submit changes to "contrib" areas for the maintainer to examine.
The maintainer then chooses which changes are going to become a
@@ -734,7 +734,7 @@
<listitem><para id='git-commands-clone'>
<emphasis><filename>git clone</filename>:</emphasis>
Creates a local clone of a Git repository that is on
- equal footing with a fellow developer’s Git repository
+ equal footing with a fellow developer's Git repository
or an upstream repository.
</para></listitem>
<listitem><para>
@@ -752,7 +752,7 @@
Commits are used for historical purposes, for determining
if a maintainer of a project will allow the change,
and for ultimately pushing the change from your local
- Git repository into the project’s upstream repository.
+ Git repository into the project's upstream repository.
</para></listitem>
<listitem><para>
<emphasis><filename>git status</filename>:</emphasis>
diff --git a/poky/documentation/overview-manual/overview-manual-intro.rst b/poky/documentation/overview-manual/overview-manual-intro.rst
new file mode 100644
index 0000000..3f206fd
--- /dev/null
+++ b/poky/documentation/overview-manual/overview-manual-intro.rst
@@ -0,0 +1,74 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+**********************************************
+The Yocto Project Overview and Concepts Manual
+**********************************************
+
+.. _overview-manual-welcome:
+
+Welcome
+=======
+
+Welcome to the Yocto Project Overview and Concepts Manual! This manual
+introduces the Yocto Project by providing concepts, software overviews,
+best-known-methods (BKMs), and any other high-level introductory
+information suitable for a new Yocto Project user.
+
+The following list describes what you can get from this manual:
+
+- `Introducing the Yocto Project <#overview-yp>`__\ *:* This chapter
+ provides an introduction to the Yocto Project. You will learn about
+ features and challenges of the Yocto Project, the layer model,
+ components and tools, development methods, the
+ :term:`Poky` reference distribution, the
+ OpenEmbedded build system workflow, and some basic Yocto terms.
+
+- `The Yocto Project Development
+ Environment <#overview-development-environment>`__\ *:* This chapter
+ helps you get started understanding the Yocto Project development
+ environment. You will learn about open source, development hosts,
+ Yocto Project source repositories, workflows using Git and the Yocto
+ Project, a Git primer, and information about licensing.
+
+- :doc:`overview-manual-concepts` *:* This
+ chapter presents various concepts regarding the Yocto Project. You
+ can find conceptual information about components, development,
+ cross-toolchains, and so forth.
+
+This manual does not give you the following:
+
+- *Step-by-step Instructions for Development Tasks:* Instructional
+ procedures reside in other manuals within the Yocto Project
+ documentation set. For example, the :doc:`../dev-manual/dev-manual`
+ provides examples on how to perform
+ various development tasks. As another example, the
+ :doc:`../sdk-manual/sdk-manual` manual contains detailed
+ instructions on how to install an SDK, which is used to develop
+ applications for target hardware.
+
+- *Reference Material:* This type of material resides in an appropriate
+ reference manual. For example, system variables are documented in the
+ :doc:`../ref-manual/ref-manual`. As another
+ example, the :doc:`../bsp-guide/bsp-guide` contains reference information on
+ BSPs.
+
+- *Detailed Public Information Not Specific to the Yocto Project:* For
+ example, exhaustive information on how to use the Source Control
+ Manager Git is better covered with Internet searches and official Git
+ Documentation than through the Yocto Project documentation.
+
+.. _overview-manual-other-information:
+
+Other Information
+=================
+
+Because this manual presents information for many different topics,
+supplemental information is recommended for full comprehension. For
+additional introductory information on the Yocto Project, see the
+:yocto_home:`Yocto Project Website <>`. If you want to build an image
+with no knowledge of Yocto Project as a way of quickly testing it out,
+see the :doc:`../brief-yoctoprojectqs/brief-yoctoprojectqs` document.
+For a comprehensive list of links and other documentation, see the
+":ref:`Links and Related
+Documentation <resources-links-and-related-documentation>`"
+section in the Yocto Project Reference Manual.
diff --git a/poky/documentation/overview-manual/overview-manual-yp-intro.rst b/poky/documentation/overview-manual/overview-manual-yp-intro.rst
new file mode 100644
index 0000000..265fbda
--- /dev/null
+++ b/poky/documentation/overview-manual/overview-manual-yp-intro.rst
@@ -0,0 +1,941 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+*****************************
+Introducing the Yocto Project
+*****************************
+
+What is the Yocto Project?
+==========================
+
+The Yocto Project is an open source collaboration project that helps
+developers create custom Linux-based systems that are designed for
+embedded products regardless of the product's hardware architecture.
+Yocto Project provides a flexible toolset and a development environment
+that allows embedded device developers across the world to collaborate
+through shared technologies, software stacks, configurations, and best
+practices used to create these tailored Linux images.
+
+Thousands of developers worldwide have discovered that Yocto Project
+provides advantages in both systems and applications development,
+archival and management benefits, and customizations used for speed,
+footprint, and memory utilization. The project is a standard when it
+comes to delivering embedded software stacks. The project allows
+software customizations and build interchange for multiple hardware
+platforms as well as software stacks that can be maintained and scaled.
+
+.. image:: figures/key-dev-elements.png
+ :align: center
+
+For further introductory information on the Yocto Project, you might be
+interested in this
+`article <https://www.embedded.com/electronics-blogs/say-what-/4458600/Why-the-Yocto-Project-for-my-IoT-Project->`__
+by Drew Moseley and in this short introductory
+`video <https://www.youtube.com/watch?v=utZpKM7i5Z4>`__.
+
+The remainder of this section overviews advantages and challenges tied
+to the Yocto Project.
+
+.. _gs-features:
+
+Features
+--------
+
+The following list describes features and advantages of the Yocto
+Project:
+
+- *Widely Adopted Across the Industry:* Semiconductor, operating
+ system, software, and service vendors exist whose products and
+ services adopt and support the Yocto Project. For a look at the Yocto
+ Project community and the companies involved with the Yocto Project,
+ see the "COMMUNITY" and "ECOSYSTEM" tabs on the
+ :yocto_home:`Yocto Project <>` home page.
+
+- *Architecture Agnostic:* Yocto Project supports Intel, ARM, MIPS,
+ AMD, PPC and other architectures. Most ODMs, OSVs, and chip vendors
+ create and supply BSPs that support their hardware. If you have
+ custom silicon, you can create a BSP that supports that architecture.
+
+ Aside from lots of architecture support, the Yocto Project fully
+ supports a wide range of device emulation through the Quick EMUlator
+ (QEMU).
+
+- *Images and Code Transfer Easily:* Yocto Project output can easily
+ move between architectures without moving to new development
+ environments. Additionally, if you have used the Yocto Project to
+ create an image or application and you find yourself not able to
+ support it, commercial Linux vendors such as Wind River, Mentor
+ Graphics, Timesys, and ENEA could take it and provide ongoing
+ support. These vendors have offerings that are built using the Yocto
+ Project.
+
+- *Flexibility:* Corporations use the Yocto Project many different
+ ways. One example is to create an internal Linux distribution as a
+ code base the corporation can use across multiple product groups.
+ Through customization and layering, a project group can leverage the
+ base Linux distribution to create a distribution that works for their
+ product needs.
+
+- *Ideal for Constrained Embedded and IoT devices:* Unlike a full Linux
+ distribution, you can use the Yocto Project to create exactly what
+ you need for embedded devices. You only add the feature support or
+ packages that you absolutely need for the device. For devices that
+ have display hardware, you can use available system components such
+ as X11, GTK+, Qt, Clutter, and SDL (among others) to create a rich
+ user experience. For devices that do not have a display or where you
+ want to use alternative UI frameworks, you can choose to not install
+ these components.
+
+- *Comprehensive Toolchain Capabilities:* Toolchains for supported
+ architectures satisfy most use cases. However, if your hardware
+ supports features that are not part of a standard toolchain, you can
+ easily customize that toolchain through specification of
+ platform-specific tuning parameters. And, should you need to use a
+ third-party toolchain, mechanisms built into the Yocto Project allow
+ for that.
+
+- *Mechanism Rules Over Policy:* Focusing on mechanism rather than
+ policy ensures that you are free to set policies based on the needs
+ of your design instead of adopting decisions enforced by some system
+ software provider.
+
+- *Uses a Layer Model:* The Yocto Project `layer
+ infrastructure <#the-yocto-project-layer-model>`__ groups related
+ functionality into separate bundles. You can incrementally add these
+ grouped functionalities to your project as needed. Using layers to
+ isolate and group functionality reduces project complexity and
+ redundancy, allows you to easily extend the system, make
+ customizations, and keep functionality organized.
+
+- *Supports Partial Builds:* You can build and rebuild individual
+ packages as needed. Yocto Project accomplishes this through its
+ `shared-state cache <#shared-state-cache>`__ (sstate) scheme. Being
+ able to build and debug components individually eases project
+ development.
+
+- *Releases According to a Strict Schedule:* Major releases occur on a
+ :doc:`six-month cycle <../ref-manual/ref-release-process>`
+ predictably in October and April. The most recent two releases
+ support point releases to address common vulnerabilities and
+ exposures. This predictability is crucial for projects based on the
+ Yocto Project and allows development teams to plan activities.
+
+- *Rich Ecosystem of Individuals and Organizations:* For open source
+ projects, the value of community is very important. Support forums,
+ expertise, and active developers who continue to push the Yocto
+ Project forward are readily available.
+
+- *Binary Reproducibility:* The Yocto Project allows you to be very
+ specific about dependencies and achieves very high percentages of
+ binary reproducibility (e.g. 99.8% for ``core-image-minimal``). When
+ distributions are not specific about which packages are pulled in and
+ in what order to support dependencies, other build systems can
+ arbitrarily include packages.
+
+- *License Manifest:* The Yocto Project provides a :ref:`license
+ manifest <dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle>`
+ for review by people who need to track the use of open source
+ licenses (e.g. legal teams).
+
+.. _gs-challenges:
+
+Challenges
+----------
+
+The following list presents challenges you might encounter when
+developing using the Yocto Project:
+
+- *Steep Learning Curve:* The Yocto Project has a steep learning curve
+ and has many different ways to accomplish similar tasks. It can be
+ difficult to choose how to proceed when varying methods exist by
+ which to accomplish a given task.
+
+- *Understanding What Changes You Need to Make For Your Design Requires
+ Some Research:* Beyond the simple tutorial stage, understanding what
+ changes need to be made for your particular design can require a
+ significant amount of research and investigation. For information
+ that helps you transition from trying out the Yocto Project to using
+ it for your project, see the ":ref:`what-i-wish-id-known:what i wish i'd known about yocto project`" and
+ ":ref:`transitioning-to-a-custom-environment:transitioning to a custom environment for systems development`"
+ documents on the Yocto Project website.
+
+- *Project Workflow Could Be Confusing:* The `Yocto Project
+ workflow <#overview-development-environment>`__ could be confusing if
+ you are used to traditional desktop and server software development.
+ In a desktop development environment, mechanisms exist to easily pull
+ and install new packages, which are typically pre-compiled binaries
+ from servers accessible over the Internet. Using the Yocto Project,
+ you must modify your configuration and rebuild to add additional
+ packages.
+
+- *Working in a Cross-Build Environment Can Feel Unfamiliar:* When
+ developing code to run on a target, compilation, execution, and
+ testing done on the actual target can be faster than running a
+ BitBake build on a development host and then deploying binaries to
+ the target for test. While the Yocto Project does support development
+ tools on the target, the additional step of integrating your changes
+ back into the Yocto Project build environment would be required.
+ Yocto Project supports an intermediate approach that involves making
+ changes on the development system within the BitBake environment and
+ then deploying only the updated packages to the target.
+
+ The Yocto Project :term:`OpenEmbedded Build System`
+ produces packages
+ in standard formats (i.e. RPM, DEB, IPK, and TAR). You can deploy
+ these packages into the running system on the target by using
+ utilities on the target such as ``rpm`` or ``ipk``.
+
+- *Initial Build Times Can be Significant:* Long initial build times
+ are unfortunately unavoidable due to the large number of packages
+ initially built from scratch for a fully functioning Linux system.
+ Once that initial build is completed, however, the shared-state
+ (sstate) cache mechanism Yocto Project uses keeps the system from
+ rebuilding packages that have not been "touched" since the last
+ build. The sstate mechanism significantly reduces times for
+ successive builds.
+
+The Yocto Project Layer Model
+=============================
+
+The Yocto Project's "Layer Model" is a development model for embedded
+and IoT Linux creation that distinguishes the Yocto Project from other
+simple build systems. The Layer Model simultaneously supports
+collaboration and customization. Layers are repositories that contain
+related sets of instructions that tell the :term:`OpenEmbedded Build System`
+what to do. You can
+collaborate, share, and reuse layers.
+
+Layers can contain changes to previous instructions or settings at any
+time. This powerful override capability is what allows you to customize
+previously supplied collaborative or community layers to suit your
+product requirements.
+
+You use different layers to logically separate information in your
+build. As an example, you could have BSP, GUI, distro configuration,
+middleware, or application layers. Putting your entire build into one
+layer limits and complicates future customization and reuse. Isolating
+information into layers, on the other hand, helps simplify future
+customizations and reuse. You might find it tempting to keep everything
+in one layer when working on a single project. However, the more modular
+your Metadata, the easier it is to cope with future changes.
+
+.. note::
+
+ - Use Board Support Package (BSP) layers from silicon vendors when
+ possible.
+
+ - Familiarize yourself with the `Yocto Project curated layer
+ index <https://caffelli-staging.yoctoproject.org/software-overview/layers/>`__
+ or the `OpenEmbedded layer
+ index <http://layers.openembedded.org/layerindex/branch/master/layers/>`__.
+ The latter contains more layers but they are less universally
+ validated.
+
+ - Layers support the inclusion of technologies, hardware components,
+ and software components. The :ref:`Yocto Project
+ Compatible <dev-manual/dev-manual-common-tasks:making sure your layer is compatible with yocto project>`
+ designation provides a minimum level of standardization that
+ contributes to a strong ecosystem. "YP Compatible" is applied to
+ appropriate products and software components such as BSPs, other
+ OE-compatible layers, and related open-source projects, allowing
+ the producer to use Yocto Project badges and branding assets.
+
+To illustrate how layers are used to keep things modular, consider
+machine customizations. These types of customizations typically reside
+in a special layer, rather than a general layer, called a BSP Layer.
+Furthermore, the machine customizations should be isolated from recipes
+and Metadata that support a new GUI environment, for example. This
+situation gives you a couple of layers: one for the machine
+configurations, and one for the GUI environment. It is important to
+understand, however, that the BSP layer can still make machine-specific
+additions to recipes within the GUI environment layer without polluting
+the GUI layer itself with those machine-specific changes. You can
+accomplish this through a recipe that is a BitBake append
+(``.bbappend``) file, which is described later in this section.
+
+.. note::
+
+ For general information on BSP layer structure, see the
+ :doc:`../bsp-guide/bsp-guide`
+ .
+
+The :term:`Source Directory`
+contains both general layers and BSP layers right out of the box. You
+can easily identify layers that ship with a Yocto Project release in the
+Source Directory by their names. Layers typically have names that begin
+with the string ``meta-``.
+
+.. note::
+
+ It is not a requirement that a layer name begin with the prefix
+ meta-
+ , but it is a commonly accepted standard in the Yocto Project
+ community.
+
+For example, if you were to examine the `tree
+view <https://git.yoctoproject.org/cgit/cgit.cgi/poky/tree/>`__ of the
+``poky`` repository, you will see several layers: ``meta``,
+``meta-skeleton``, ``meta-selftest``, ``meta-poky``, and
+``meta-yocto-bsp``. Each of these repositories represents a distinct
+layer.
+
+For procedures on how to create layers, see the
+":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`"
+section in the Yocto Project Development Tasks Manual.
+
+Components and Tools
+====================
+
+The Yocto Project employs a collection of components and tools used by
+the project itself, by project developers, and by those using the Yocto
+Project. These components and tools are open source projects and
+metadata that are separate from the reference distribution
+(:term:`Poky`) and the
+:term:`OpenEmbedded Build System`. Most of the
+components and tools are downloaded separately.
+
+This section provides brief overviews of the components and tools
+associated with the Yocto Project.
+
+.. _gs-development-tools:
+
+Development Tools
+-----------------
+
+The following list consists of tools that help you develop images and
+applications using the Yocto Project:
+
+- *CROPS:* `CROPS <https://github.com/crops/poky-container/>`__ is an
+ open source, cross-platform development framework that leverages
+ `Docker Containers <https://www.docker.com/>`__. CROPS provides an
+ easily managed, extensible environment that allows you to build
+ binaries for a variety of architectures on Windows, Linux and Mac OS
+ X hosts.
+
+- *devtool:* This command-line tool is available as part of the
+ extensible SDK (eSDK) and is its cornerstone. You can use ``devtool``
+ to help build, test, and package software within the eSDK. You can
+ use the tool to optionally integrate what you build into an image
+ built by the OpenEmbedded build system.
+
+ The ``devtool`` command employs a number of sub-commands that allow
+ you to add, modify, and upgrade recipes. As with the OpenEmbedded
+ build system, "recipes" represent software packages within
+ ``devtool``. When you use ``devtool add``, a recipe is automatically
+ created. When you use ``devtool modify``, the specified existing
+ recipe is used in order to determine where to get the source code and
+ how to patch it. In both cases, an environment is set up so that when
+ you build the recipe a source tree that is under your control is used
+ in order to allow you to make changes to the source as desired. By
+ default, both new recipes and the source go into a "workspace"
+ directory under the eSDK. The ``devtool upgrade`` command updates an
+ existing recipe so that you can build it for an updated set of source
+ files.
+
+ You can read about the ``devtool`` workflow in the Yocto Project
+ Application Development and Extensible Software Development Kit
+ (eSDK) Manual in the
+ ":ref:`sdk-manual/sdk-extensible:using \`\`devtool\`\` in your sdk workflow`"
+ section.
+
+- *Extensible Software Development Kit (eSDK):* The eSDK provides a
+ cross-development toolchain and libraries tailored to the contents of
+ a specific image. The eSDK makes it easy to add new applications and
+ libraries to an image, modify the source for an existing component,
+ test changes on the target hardware, and integrate into the rest of
+ the OpenEmbedded build system. The eSDK gives you a toolchain
+ experience supplemented with the powerful set of ``devtool`` commands
+ tailored for the Yocto Project environment.
+
+ For information on the eSDK, see the :doc:`../sdk-manual/sdk-manual` Manual.
+
+- *Toaster:* Toaster is a web interface to the Yocto Project
+ OpenEmbedded build system. Toaster allows you to configure, run, and
+ view information about builds. For information on Toaster, see the
+ :doc:`../toaster-manual/toaster-manual`.
+
+.. _gs-production-tools:
+
+Production Tools
+----------------
+
+The following list consists of tools that help production related
+activities using the Yocto Project:
+
+- *Auto Upgrade Helper:* This utility when used in conjunction with the
+ :term:`OpenEmbedded Build System`
+ (BitBake and
+ OE-Core) automatically generates upgrades for recipes that are based
+ on new versions of the recipes published upstream. See
+ :ref:`dev-manual/dev-manual-common-tasks:using the auto upgrade helper (auh)`
+ for how to set it up.
+
+- *Recipe Reporting System:* The Recipe Reporting System tracks recipe
+ versions available for Yocto Project. The main purpose of the system
+ is to help you manage the recipes you maintain and to offer a dynamic
+ overview of the project. The Recipe Reporting System is built on top
+ of the `OpenEmbedded Layer
+ Index <http://layers.openembedded.org/layerindex/layers/>`__, which
+ is a website that indexes OpenEmbedded-Core layers.
+
+- *Patchwork:* `Patchwork <http://jk.ozlabs.org/projects/patchwork/>`__
+ is a fork of a project originally started by
+ `OzLabs <http://ozlabs.org/>`__. The project is a web-based tracking
+ system designed to streamline the process of bringing contributions
+ into a project. The Yocto Project uses Patchwork as an organizational
+ tool to handle patches, which number in the thousands for every
+ release.
+
+- *AutoBuilder:* AutoBuilder is a project that automates build tests
+ and quality assurance (QA). By using the public AutoBuilder, anyone
+ can determine the status of the current "master" branch of Poky.
+
+ .. note::
+
+ AutoBuilder is based on buildbot.
+
+ A goal of the Yocto Project is to lead the open source industry with
+ a project that automates testing and QA procedures. In doing so, the
+ project encourages a development community that publishes QA and test
+ plans, publicly demonstrates QA and test plans, and encourages
+ development of tools that automate and test and QA procedures for the
+ benefit of the development community.
+
+ You can learn more about the AutoBuilder used by the Yocto Project
+ Autobuilder :doc:`here <../test-manual/test-manual-understand-autobuilder>`.
+
+- *Cross-Prelink:* Prelinking is the process of pre-computing the load
+ addresses and link tables generated by the dynamic linker as compared
+ to doing this at runtime. Doing this ahead of time results in
+ performance improvements when the application is launched and reduced
+ memory usage for libraries shared by many applications.
+
+ Historically, cross-prelink is a variant of prelink, which was
+ conceived by `Jakub
+ Jelínek <http://people.redhat.com/jakub/prelink.pdf>`__ a number of
+ years ago. Both prelink and cross-prelink are maintained in the same
+ repository albeit on separate branches. By providing an emulated
+ runtime dynamic linker (i.e. ``glibc``-derived ``ld.so`` emulation),
+ the cross-prelink project extends the prelink software's ability to
+ prelink a sysroot environment. Additionally, the cross-prelink
+ software enables the ability to work in sysroot style environments.
+
+ The dynamic linker determines standard load address calculations
+ based on a variety of factors such as mapping addresses, library
+ usage, and library function conflicts. The prelink tool uses this
+ information, from the dynamic linker, to determine unique load
+ addresses for executable and linkable format (ELF) binaries that are
+ shared libraries and dynamically linked. The prelink tool modifies
+ these ELF binaries with the pre-computed information. The result is
+ faster loading and often lower memory consumption because more of the
+ library code can be re-used from shared Copy-On-Write (COW) pages.
+
+ The original upstream prelink project only supports running prelink
+ on the end target device due to the reliance on the target device's
+ dynamic linker. This restriction causes issues when developing a
+ cross-compiled system. The cross-prelink adds a synthesized dynamic
+ loader that runs on the host, thus permitting cross-prelinking
+ without ever having to run on a read-write target filesystem.
+
+- *Pseudo:* Pseudo is the Yocto Project implementation of
+ `fakeroot <http://man.he.net/man1/fakeroot>`__, which is used to run
+ commands in an environment that seemingly has root privileges.
+
+ During a build, it can be necessary to perform operations that
+ require system administrator privileges. For example, file ownership
+ or permissions might need definition. Pseudo is a tool that you can
+ either use directly or through the environment variable
+ ``LD_PRELOAD``. Either method allows these operations to succeed as
+ if system administrator privileges exist even when they do not.
+
+ You can read more about Pseudo in the "`Fakeroot and
+ Pseudo <#fakeroot-and-pseudo>`__" section.
+
+.. _gs-openembedded-build-system:
+
+Open-Embedded Build System Components
+-------------------------------------
+
+The following list consists of components associated with the
+:term:`OpenEmbedded Build System`:
+
+- *BitBake:* BitBake is a core component of the Yocto Project and is
+ used by the OpenEmbedded build system to build images. While BitBake
+ is key to the build system, BitBake is maintained separately from the
+ Yocto Project.
+
+ BitBake is a generic task execution engine that allows shell and
+ Python tasks to be run efficiently and in parallel while working
+ within complex inter-task dependency constraints. In short, BitBake
+ is a build engine that works through recipes written in a specific
+ format in order to perform sets of tasks.
+
+ You can learn more about BitBake in the :doc:`BitBake User
+ Manual <bitbake:index>`.
+
+- *OpenEmbedded-Core:* OpenEmbedded-Core (OE-Core) is a common layer of
+ metadata (i.e. recipes, classes, and associated files) used by
+ OpenEmbedded-derived systems, which includes the Yocto Project. The
+ Yocto Project and the OpenEmbedded Project both maintain the
+ OpenEmbedded-Core. You can find the OE-Core metadata in the Yocto
+ Project :yocto_git:`Source Repositories </cgit/cgit.cgi/poky/tree/meta>`.
+
+ Historically, the Yocto Project integrated the OE-Core metadata
+ throughout the Yocto Project source repository reference system
+ (Poky). After Yocto Project Version 1.0, the Yocto Project and
+ OpenEmbedded agreed to work together and share a common core set of
+ metadata (OE-Core), which contained much of the functionality
+ previously found in Poky. This collaboration achieved a long-standing
+ OpenEmbedded objective for having a more tightly controlled and
+ quality-assured core. The results also fit well with the Yocto
+ Project objective of achieving a smaller number of fully featured
+ tools as compared to many different ones.
+
+ Sharing a core set of metadata results in Poky as an integration
+ layer on top of OE-Core. You can see that in this
+ `figure <#yp-key-dev-elements>`__. The Yocto Project combines various
+ components such as BitBake, OE-Core, script "glue", and documentation
+ for its build system.
+
+.. _gs-reference-distribution-poky:
+
+Reference Distribution (Poky)
+-----------------------------
+
+Poky is the Yocto Project reference distribution. It contains the
+:term:`OpenEmbedded Build System`
+(BitBake and OE-Core) as well as a set of metadata to get you started
+building your own distribution. See the
+`figure <#what-is-the-yocto-project>`__ in "What is the Yocto Project?"
+section for an illustration that shows Poky and its relationship with
+other parts of the Yocto Project.
+
+To use the Yocto Project tools and components, you can download
+(``clone``) Poky and use it to bootstrap your own distribution.
+
+.. note::
+
+ Poky does not contain binary files. It is a working example of how to
+ build your own custom Linux distribution from source.
+
+You can read more about Poky in the "`Reference Embedded Distribution
+(Poky) <#reference-embedded-distribution>`__" section.
+
+.. _gs-packages-for-finished-targets:
+
+Packages for Finished Targets
+-----------------------------
+
+The following lists components associated with packages for finished
+targets:
+
+- *Matchbox:* Matchbox is an Open Source, base environment for the X
+ Window System running on non-desktop, embedded platforms such as
+ handhelds, set-top boxes, kiosks, and anything else for which screen
+ space, input mechanisms, or system resources are limited.
+
+ Matchbox consists of a number of interchangeable and optional
+ applications that you can tailor to a specific, non-desktop platform
+ to enhance usability in constrained environments.
+
+ You can find the Matchbox source in the Yocto Project
+ :yocto_git:`Source Repositories <>`.
+
+- *Opkg:* Open PacKaGe management (opkg) is a lightweight package
+ management system based on the itsy package (ipkg) management system.
+ Opkg is written in C and resembles Advanced Package Tool (APT) and
+ Debian Package (dpkg) in operation.
+
+ Opkg is intended for use on embedded Linux devices and is used in
+ this capacity in the
+ `OpenEmbedded <http://www.openembedded.org/wiki/Main_Page>`__ and
+ `OpenWrt <https://openwrt.org/>`__ projects, as well as the Yocto
+ Project.
+
+ .. note::
+
+ As best it can, opkg maintains backwards compatibility with ipkg
+ and conforms to a subset of Debian's policy manual regarding
+ control files.
+
+ You can find the opkg source in the Yocto Project
+ :yocto_git:`Source Repositories <>`.
+
+.. _gs-archived-components:
+
+Archived Components
+-------------------
+
+The Build Appliance is a virtual machine image that enables you to build
+and boot a custom embedded Linux image with the Yocto Project using a
+non-Linux development system.
+
+Historically, the Build Appliance was the second of three methods by
+which you could use the Yocto Project on a system that was not native to
+Linux.
+
+1. *Hob:* Hob, which is now deprecated and is no longer available since
+ the 2.1 release of the Yocto Project provided a rudimentary,
+ GUI-based interface to the Yocto Project. Toaster has fully replaced
+ Hob.
+
+2. *Build Appliance:* Post Hob, the Build Appliance became available. It
+ was never recommended that you use the Build Appliance as a
+ day-to-day production development environment with the Yocto Project.
+ Build Appliance was useful as a way to try out development in the
+ Yocto Project environment.
+
+3. *CROPS:* The final and best solution available now for developing
+ using the Yocto Project on a system not native to Linux is with
+ `CROPS <#gs-crops-overview>`__.
+
+.. _gs-development-methods:
+
+Development Methods
+===================
+
+The Yocto Project development environment usually involves a
+:term:`Build Host` and target
+hardware. You use the Build Host to build images and develop
+applications, while you use the target hardware to test deployed
+software.
+
+This section provides an introduction to the choices or development
+methods you have when setting up your Build Host. Depending on the your
+particular workflow preference and the type of operating system your
+Build Host runs, several choices exist that allow you to use the Yocto
+Project.
+
+.. note::
+
+ For additional detail about the Yocto Project development
+ environment, see the ":doc:`overview-manual-development-environment`"
+ chapter.
+
+- *Native Linux Host:* By far the best option for a Build Host. A
+ system running Linux as its native operating system allows you to
+ develop software by directly using the
+ :term:`BitBake` tool. You can
+ accomplish all aspects of development from a familiar shell of a
+ supported Linux distribution.
+
+ For information on how to set up a Build Host on a system running
+ Linux as its native operating system, see the
+ ":ref:`dev-manual/dev-manual-start:setting up a native linux host`"
+ section in the Yocto Project Development Tasks Manual.
+
+- *CROss PlatformS (CROPS):* Typically, you use
+ `CROPS <https://github.com/crops/poky-container/>`__, which leverages
+ `Docker Containers <https://www.docker.com/>`__, to set up a Build
+ Host that is not running Linux (e.g. Microsoft Windows or macOS).
+
+ .. note::
+
+ You can, however, use CROPS on a Linux-based system.
+
+ CROPS is an open source, cross-platform development framework that
+ provides an easily managed, extensible environment for building
+ binaries targeted for a variety of architectures on Windows, macOS,
+ or Linux hosts. Once the Build Host is set up using CROPS, you can
+ prepare a shell environment to mimic that of a shell being used on a
+ system natively running Linux.
+
+ For information on how to set up a Build Host with CROPS, see the
+ ":ref:`dev-manual/dev-manual-start:setting up to use cross platforms (crops)`"
+ section in the Yocto Project Development Tasks Manual.
+
+- *Windows Subsystem For Linux (WSLv2):* You may use Windows Subsystem
+ For Linux v2 to set up a build host using Windows 10.
+
+ .. note::
+
+ The Yocto Project is not compatible with WSLv1, it is compatible
+ but not officially supported nor validated with WSLv2, if you
+ still decide to use WSL please upgrade to WSLv2.
+
+ The Windows Subsystem For Linux allows Windows 10 to run a real Linux
+ kernel inside of a lightweight utility virtual machine (VM) using
+ virtualization technology.
+
+ For information on how to set up a Build Host with WSLv2, see the
+ ":ref:`dev-manual/dev-manual-start:setting up to use windows subsystem for linux (wslv2)`"
+ section in the Yocto Project Development Tasks Manual.
+
+- *Toaster:* Regardless of what your Build Host is running, you can use
+ Toaster to develop software using the Yocto Project. Toaster is a web
+ interface to the Yocto Project's :term:`OpenEmbedded Build System`.
+ The interface
+ enables you to configure and run your builds. Information about
+ builds is collected and stored in a database. You can use Toaster to
+ configure and start builds on multiple remote build servers.
+
+ For information about and how to use Toaster, see the
+ :doc:`../toaster-manual/toaster-manual`.
+
+.. _reference-embedded-distribution:
+
+Reference Embedded Distribution (Poky)
+======================================
+
+"Poky", which is pronounced *Pock*-ee, is the name of the Yocto
+Project's reference distribution or Reference OS Kit. Poky contains the
+:term:`OpenEmbedded Build System`
+(:term:`BitBake` and
+:term:`OpenEmbedded-Core (OE-Core)`) as well as a set
+of :term:`Metadata` to get you started
+building your own distro. In other words, Poky is a base specification
+of the functionality needed for a typical embedded system as well as the
+components from the Yocto Project that allow you to build a distribution
+into a usable binary image.
+
+Poky is a combined repository of BitBake, OpenEmbedded-Core (which is
+found in ``meta``), ``meta-poky``, ``meta-yocto-bsp``, and documentation
+provided all together and known to work well together. You can view
+these items that make up the Poky repository in the
+:yocto_git:`Source Repositories </cgit/cgit.cgi/poky/tree/>`.
+
+.. note::
+
+ If you are interested in all the contents of the
+ poky
+ Git repository, see the ":ref:`ref-manual/ref-structure:top-level core components`"
+ section in the Yocto Project Reference Manual.
+
+The following figure illustrates what generally comprises Poky:
+
+.. image:: figures/poky-reference-distribution.png
+ :align: center
+
+- BitBake is a task executor and scheduler that is the heart of the
+ OpenEmbedded build system.
+
+- ``meta-poky``, which is Poky-specific metadata.
+
+- ``meta-yocto-bsp``, which are Yocto Project-specific Board Support
+ Packages (BSPs).
+
+- OpenEmbedded-Core (OE-Core) metadata, which includes shared
+ configurations, global variable definitions, shared classes,
+ packaging, and recipes. Classes define the encapsulation and
+ inheritance of build logic. Recipes are the logical units of software
+ and images to be built.
+
+- Documentation, which contains the Yocto Project source files used to
+ make the set of user manuals.
+
+.. note::
+
+ While Poky is a "complete" distribution specification and is tested
+ and put through QA, you cannot use it as a product "out of the box"
+ in its current form.
+
+To use the Yocto Project tools, you can use Git to clone (download) the
+Poky repository then use your local copy of the reference distribution
+to bootstrap your own distribution.
+
+.. note::
+
+ Poky does not contain binary files. It is a working example of how to
+ build your own custom Linux distribution from source.
+
+Poky has a regular, well established, six-month release cycle under its
+own version. Major releases occur at the same time major releases (point
+releases) occur for the Yocto Project, which are typically in the Spring
+and Fall. For more information on the Yocto Project release schedule and
+cadence, see the ":doc:`../ref-manual/ref-release-process`" chapter in the
+Yocto Project Reference Manual.
+
+Much has been said about Poky being a "default configuration". A default
+configuration provides a starting image footprint. You can use Poky out
+of the box to create an image ranging from a shell-accessible minimal
+image all the way up to a Linux Standard Base-compliant image that uses
+a GNOME Mobile and Embedded (GMAE) based reference user interface called
+Sato.
+
+One of the most powerful properties of Poky is that every aspect of a
+build is controlled by the metadata. You can use metadata to augment
+these base image types by adding metadata
+`layers <#the-yocto-project-layer-model>`__ that extend functionality.
+These layers can provide, for example, an additional software stack for
+an image type, add a board support package (BSP) for additional
+hardware, or even create a new image type.
+
+Metadata is loosely grouped into configuration files or package recipes.
+A recipe is a collection of non-executable metadata used by BitBake to
+set variables or define additional build-time tasks. A recipe contains
+fields such as the recipe description, the recipe version, the license
+of the package and the upstream source repository. A recipe might also
+indicate that the build process uses autotools, make, distutils or any
+other build process, in which case the basic functionality can be
+defined by the classes it inherits from the OE-Core layer's class
+definitions in ``./meta/classes``. Within a recipe you can also define
+additional tasks as well as task prerequisites. Recipe syntax through
+BitBake also supports both ``_prepend`` and ``_append`` operators as a
+method of extending task functionality. These operators inject code into
+the beginning or end of a task. For information on these BitBake
+operators, see the
+":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:appending and prepending (override style syntax)`"
+section in the BitBake User's Manual.
+
+.. _openembedded-build-system-workflow:
+
+The OpenEmbedded Build System Workflow
+======================================
+
+The :term:`OpenEmbedded Build System` uses a "workflow" to
+accomplish image and SDK generation. The following figure overviews that
+workflow:
+
+.. image:: figures/YP-flow-diagram.png
+ :align: center
+
+Following is a brief summary of the "workflow":
+
+1. Developers specify architecture, policies, patches and configuration
+ details.
+
+2. The build system fetches and downloads the source code from the
+ specified location. The build system supports standard methods such
+ as tarballs or source code repositories systems such as Git.
+
+3. Once source code is downloaded, the build system extracts the sources
+ into a local work area where patches are applied and common steps for
+ configuring and compiling the software are run.
+
+4. The build system then installs the software into a temporary staging
+ area where the binary package format you select (DEB, RPM, or IPK) is
+ used to roll up the software.
+
+5. Different QA and sanity checks run throughout entire build process.
+
+6. After the binaries are created, the build system generates a binary
+ package feed that is used to create the final root file image.
+
+7. The build system generates the file system image and a customized
+ Extensible SDK (eSDK) for application development in parallel.
+
+For a very detailed look at this workflow, see the "`OpenEmbedded Build
+System Concepts <#openembedded-build-system-build-concepts>`__" section.
+
+Some Basic Terms
+================
+
+It helps to understand some basic fundamental terms when learning the
+Yocto Project. Although a list of terms exists in the ":doc:`Yocto Project
+Terms <../ref-manual/ref-terms>`" section of the Yocto Project
+Reference Manual, this section provides the definitions of some terms
+helpful for getting started:
+
+- *Configuration Files:* Files that hold global definitions of
+ variables, user-defined variables, and hardware configuration
+ information. These files tell the :term:`OpenEmbedded Build System`
+ what to build and
+ what to put into the image to support a particular platform.
+
+- *Extensible Software Development Kit (eSDK):* A custom SDK for
+ application developers. This eSDK allows developers to incorporate
+ their library and programming changes back into the image to make
+ their code available to other application developers. For information
+ on the eSDK, see the :doc:`../sdk-manual/sdk-manual` manual.
+
+- *Layer:* A collection of related recipes. Layers allow you to
+ consolidate related metadata to customize your build. Layers also
+ isolate information used when building for multiple architectures.
+ Layers are hierarchical in their ability to override previous
+ specifications. You can include any number of available layers from
+ the Yocto Project and customize the build by adding your layers after
+ them. You can search the Layer Index for layers used within Yocto
+ Project.
+
+ For more detailed information on layers, see the
+ ":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`"
+ section in the Yocto Project Development Tasks Manual. For a
+ discussion specifically on BSP Layers, see the
+ ":ref:`bsp-guide/bsp:bsp layers`" section in the Yocto
+ Project Board Support Packages (BSP) Developer's Guide.
+
+- *Metadata:* A key element of the Yocto Project is the Metadata that
+ is used to construct a Linux distribution and is contained in the
+ files that the OpenEmbedded build system parses when building an
+ image. In general, Metadata includes recipes, configuration files,
+ and other information that refers to the build instructions
+ themselves, as well as the data used to control what things get built
+ and the effects of the build. Metadata also includes commands and
+ data used to indicate what versions of software are used, from where
+ they are obtained, and changes or additions to the software itself
+ (patches or auxiliary files) that are used to fix bugs or customize
+ the software for use in a particular situation. OpenEmbedded-Core is
+ an important set of validated metadata.
+
+- *OpenEmbedded Build System:* The terms "BitBake" and "build system"
+ are sometimes used for the OpenEmbedded Build System.
+
+ BitBake is a task scheduler and execution engine that parses
+ instructions (i.e. recipes) and configuration data. After a parsing
+ phase, BitBake creates a dependency tree to order the compilation,
+ schedules the compilation of the included code, and finally executes
+ the building of the specified custom Linux image (distribution).
+ BitBake is similar to the ``make`` tool.
+
+ During a build process, the build system tracks dependencies and
+ performs a native or cross-compilation of the package. As a first
+ step in a cross-build setup, the framework attempts to create a
+ cross-compiler toolchain (i.e. Extensible SDK) suited for the target
+ platform.
+
+- *OpenEmbedded-Core (OE-Core):* OE-Core is metadata comprised of
+ foundation recipes, classes, and associated files that are meant to
+ be common among many different OpenEmbedded-derived systems,
+ including the Yocto Project. OE-Core is a curated subset of an
+ original repository developed by the OpenEmbedded community that has
+ been pared down into a smaller, core set of continuously validated
+ recipes. The result is a tightly controlled and quality-assured core
+ set of recipes.
+
+ You can see the Metadata in the ``meta`` directory of the Yocto
+ Project `Source
+ Repositories <http://git.yoctoproject.org/cgit/cgit.cgi>`__.
+
+- *Packages:* In the context of the Yocto Project, this term refers to
+ a recipe's packaged output produced by BitBake (i.e. a "baked
+ recipe"). A package is generally the compiled binaries produced from
+ the recipe's sources. You "bake" something by running it through
+ BitBake.
+
+ It is worth noting that the term "package" can, in general, have
+ subtle meanings. For example, the packages referred to in the
+ ":ref:`ref-manual/ref-system-requirements:required packages for the build host`"
+ section in the Yocto Project Reference Manual are compiled binaries
+ that, when installed, add functionality to your Linux distribution.
+
+ Another point worth noting is that historically within the Yocto
+ Project, recipes were referred to as packages - thus, the existence
+ of several BitBake variables that are seemingly mis-named, (e.g.
+ :term:`PR`,
+ :term:`PV`, and
+ :term:`PE`).
+
+- *Poky:* Poky is a reference embedded distribution and a reference
+ test configuration. Poky provides the following:
+
+ - A base-level functional distro used to illustrate how to customize
+ a distribution.
+
+ - A means by which to test the Yocto Project components (i.e. Poky
+ is used to validate the Yocto Project).
+
+ - A vehicle through which you can download the Yocto Project.
+
+ Poky is not a product level distro. Rather, it is a good starting
+ point for customization.
+
+ .. note::
+
+ Poky is an integration layer on top of OE-Core.
+
+- *Recipe:* The most common form of metadata. A recipe contains a list
+ of settings and tasks (i.e. instructions) for building packages that
+ are then used to build the binary image. A recipe describes where you
+ get source code and which patches to apply. Recipes describe
+ dependencies for libraries or for other recipes as well as
+ configuration and compilation options. Related recipes are
+ consolidated into a layer.
diff --git a/poky/documentation/overview-manual/overview-manual-yp-intro.xml b/poky/documentation/overview-manual/overview-manual-yp-intro.xml
index 2097ed3..a2a1f49 100644
--- a/poky/documentation/overview-manual/overview-manual-yp-intro.xml
+++ b/poky/documentation/overview-manual/overview-manual-yp-intro.xml
@@ -459,7 +459,7 @@
<para>The <filename>devtool</filename> command employs
a number of sub-commands that allow you to add, modify,
and upgrade recipes.
- As with the OpenEmbedded build system, “recipes”
+ As with the OpenEmbedded build system, "recipes"
represent software packages within
<filename>devtool</filename>.
When you use <filename>devtool add</filename>, a recipe
@@ -472,7 +472,7 @@
control is used in order to allow you to make changes
to the source as desired.
By default, both new recipes and the source go into
- a “workspace” directory under the eSDK.
+ a "workspace" directory under the eSDK.
The <filename>devtool upgrade</filename> command
updates an existing recipe so that you can build it
for an updated set of source files.</para>
@@ -598,7 +598,7 @@
By providing an emulated runtime dynamic linker
(i.e. <filename>glibc</filename>-derived
<filename>ld.so</filename> emulation), the
- cross-prelink project extends the prelink software’s
+ cross-prelink project extends the prelink software's
ability to prelink a sysroot environment.
Additionally, the cross-prelink software enables the
ability to work in sysroot style environments.</para>
@@ -620,7 +620,7 @@
<para>The original upstream prelink project only
supports running prelink on the end target device
- due to the reliance on the target device’s dynamic
+ due to the reliance on the target device's dynamic
linker.
This restriction causes issues when developing a
cross-compiled system.
@@ -713,7 +713,7 @@
You can see that in this
<link linkend='yp-key-dev-elements'>figure</link>.
The Yocto Project combines various components such as
- BitBake, OE-Core, script “glue”, and documentation
+ BitBake, OE-Core, script "glue", and documentation
for its build system.
</para></listitem>
</itemizedlist>
@@ -791,7 +791,7 @@
<note>
As best it can, opkg maintains backwards
compatibility with ipkg and conforms to a subset
- of Debian’s policy manual regarding control files.
+ of Debian's policy manual regarding control files.
</note>
</para></listitem>
</itemizedlist>
diff --git a/poky/documentation/overview-manual/overview-manual.rst b/poky/documentation/overview-manual/overview-manual.rst
new file mode 100644
index 0000000..80ce9aa
--- /dev/null
+++ b/poky/documentation/overview-manual/overview-manual.rst
@@ -0,0 +1,19 @@
+.. SPDX-License-Identifier: CC-BY-2.0-UK
+
+==========================================
+Yocto Project Overview and Concepts Manual
+==========================================
+
+|
+
+.. toctree::
+ :caption: Table of Contents
+ :numbered:
+
+ overview-manual-intro
+ overview-manual-yp-intro
+ overview-manual-development-environment
+ overview-manual-concepts
+ history
+
+.. include:: /boilerplate.rst