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Andrew Geisslerc9f78652020-09-18 14:11:35 -05001.. SPDX-License-Identifier: CC-BY-2.0-UK
2
3***
4FAQ
5***
6
7**Q:** How does Poky differ from `OpenEmbedded <http://www.openembedded.org/>`__?
8
9**A:** The term ``Poky`` refers to the specific reference build
10system that the Yocto Project provides. Poky is based on
11:term:`OpenEmbedded-Core (OE-Core)` and :term:`BitBake`. Thus, the
12generic term used here for the build system is the "OpenEmbedded build
13system." Development in the Yocto Project using Poky is closely tied to
14OpenEmbedded, with changes always being merged to OE-Core or BitBake
15first before being pulled back into Poky. This practice benefits both
16projects immediately.
17
18**Q:** My development system does not meet the required Git, tar, and
19Python versions. In particular, I do not have Python 3.5.0 or greater.
20Can I still use the Yocto Project?
21
22**A:** You can get the required tools on your host development system a
23couple different ways (i.e. building a tarball or downloading a
24tarball). See the "`Required Git, tar, Python and gcc
25Versions <#required-git-tar-python-and-gcc-versions>`__" section for
26steps on how to update your build tools.
27
28**Q:** How can you claim Poky / OpenEmbedded-Core is stable?
29
30**A:** There are three areas that help with stability;
31
32- The Yocto Project team keeps :term:`OpenEmbedded-Core (OE-Core)` small and
33 focused, containing around 830 recipes as opposed to the thousands
34 available in other OpenEmbedded community layers. Keeping it small
35 makes it easy to test and maintain.
36
37- The Yocto Project team runs manual and automated tests using a small,
38 fixed set of reference hardware as well as emulated targets.
39
40- The Yocto Project uses an autobuilder, which provides continuous
41 build and integration tests.
42
43**Q:** How do I get support for my board added to the Yocto Project?
44
45**A:** Support for an additional board is added by creating a Board
46Support Package (BSP) layer for it. For more information on how to
47create a BSP layer, see the
48":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`"
49section in the Yocto Project Development Tasks Manual and the
50:doc:`../bsp-guide/bsp-guide`.
51
52Usually, if the board is not completely exotic, adding support in the
53Yocto Project is fairly straightforward.
54
55**Q:** Are there any products built using the OpenEmbedded build system?
56
57**A:** The software running on the `Vernier
58LabQuest <http://vernier.com/labquest/>`__ is built using the
59OpenEmbedded build system. See the `Vernier
60LabQuest <http://www.vernier.com/products/interfaces/labq/>`__ website
61for more information. There are a number of pre-production devices using
62the OpenEmbedded build system and the Yocto Project team announces them
63as soon as they are released.
64
65**Q:** What does the OpenEmbedded build system produce as output?
66
67**A:** Because you can use the same set of recipes to create output of
68various formats, the output of an OpenEmbedded build depends on how you
69start it. Usually, the output is a flashable image ready for the target
70device.
71
72**Q:** How do I add my package to the Yocto Project?
73
74**A:** To add a package, you need to create a BitBake recipe. For
75information on how to create a BitBake recipe, see the
76":ref:`dev-manual/dev-manual-common-tasks:writing a new recipe`"
77section in the Yocto Project Development Tasks Manual.
78
79**Q:** Do I have to reflash my entire board with a new Yocto Project
80image when recompiling a package?
81
82**A:** The OpenEmbedded build system can build packages in various
83formats such as IPK for OPKG, Debian package (``.deb``), or RPM. You can
84then upgrade the packages using the package tools on the device, much
85like on a desktop distribution such as Ubuntu or Fedora. However,
86package management on the target is entirely optional.
87
88**Q:** I see the error
89'``chmod: XXXXX new permissions are r-xrwxrwx, not r-xr-xr-x``'. What is
90wrong?
91
92**A:** You are probably running the build on an NTFS filesystem. Use
93``ext2``, ``ext3``, or ``ext4`` instead.
94
95**Q:** I see lots of 404 responses for files when the OpenEmbedded build
96system is trying to download sources. Is something wrong?
97
98**A:** Nothing is wrong. The OpenEmbedded build system checks any
99configured source mirrors before downloading from the upstream sources.
100The build system does this searching for both source archives and
101pre-checked out versions of SCM-managed software. These checks help in
102large installations because it can reduce load on the SCM servers
103themselves. The address above is one of the default mirrors configured
104into the build system. Consequently, if an upstream source disappears,
105the team can place sources there so builds continue to work.
106
107**Q:** I have machine-specific data in a package for one machine only
108but the package is being marked as machine-specific in all cases, how do
109I prevent this?
110
111**A:** Set ``SRC_URI_OVERRIDES_PACKAGE_ARCH`` = "0" in the ``.bb`` file
112but make sure the package is manually marked as machine-specific for the
113case that needs it. The code that handles
114``SRC_URI_OVERRIDES_PACKAGE_ARCH`` is in the
115``meta/classes/base.bbclass`` file.
116
117**Q:** I'm behind a firewall and need to use a proxy server. How do I do
118that?
119
120**A:** Most source fetching by the OpenEmbedded build system is done by
121``wget`` and you therefore need to specify the proxy settings in a
122``.wgetrc`` file, which can be in your home directory if you are a
123single user or can be in ``/usr/local/etc/wgetrc`` as a global user
124file.
125
126Following is the applicable code for setting various proxy types in the
127``.wgetrc`` file. By default, these settings are disabled with comments.
128To use them, remove the comments: ::
129
130 # You can set the default proxies for Wget to use for http, https, and ftp.
131 # They will override the value in the environment.
132 #https_proxy = http://proxy.yoyodyne.com:18023/
133 #http_proxy = http://proxy.yoyodyne.com:18023/
134 #ftp_proxy = http://proxy.yoyodyne.com:18023/
135
136 # If you do not want to use proxy at all, set this to off.
137 #use_proxy = on
138
139The Yocto Project also includes a
140``meta-poky/conf/site.conf.sample`` file that shows how to configure CVS
141and Git proxy servers if needed. For more information on setting up
142various proxy types and configuring proxy servers, see the
143":yocto_wiki:`Working Behind a Network Proxy </wiki/Working_Behind_a_Network_Proxy>`"
144Wiki page.
145
146**Q:** What's the difference between target and target\ ``-native``?
147
148**A:** The ``*-native`` targets are designed to run on the system being
149used for the build. These are usually tools that are needed to assist
150the build in some way such as ``quilt-native``, which is used to apply
151patches. The non-native version is the one that runs on the target
152device.
153
154**Q:** I'm seeing random build failures. Help?!
155
156**A:** If the same build is failing in totally different and random
157ways, the most likely explanation is:
158
159- The hardware you are running the build on has some problem.
160
161- You are running the build under virtualization, in which case the
162 virtualization probably has bugs.
163
164The OpenEmbedded build system processes a massive amount of data that
165causes lots of network, disk and CPU activity and is sensitive to even
166single-bit failures in any of these areas. True random failures have
167always been traced back to hardware or virtualization issues.
168
169**Q:** When I try to build a native recipe, the build fails with
170``iconv.h`` problems.
171
172**A:** If you get an error message that indicates GNU ``libiconv`` is
173not in use but ``iconv.h`` has been included from ``libiconv``, you need
174to check to see if you have a previously installed version of the header
175file in ``/usr/local/include``.
176::
177
178 #error GNU libiconv not in use but included iconv.h is from libiconv
179
180If you find a previously installed
181file, you should either uninstall it or temporarily rename it and try
182the build again.
183
184This issue is just a single manifestation of "system leakage" issues
185caused when the OpenEmbedded build system finds and uses previously
186installed files during a native build. This type of issue might not be
187limited to ``iconv.h``. Be sure that leakage cannot occur from
188``/usr/local/include`` and ``/opt`` locations.
189
190**Q:** What do we need to ship for license compliance?
191
192**A:** This is a difficult question and you need to consult your lawyer
193for the answer for your specific case. It is worth bearing in mind that
194for GPL compliance, there needs to be enough information shipped to
195allow someone else to rebuild and produce the same end result you are
196shipping. This means sharing the source code, any patches applied to it,
197and also any configuration information about how that package was
198configured and built.
199
200You can find more information on licensing in the
201":ref:`overview-manual/overview-manual-development-environment:licensing`"
202section in the Yocto
203Project Overview and Concepts Manual and also in the
204":ref:`dev-manual/dev-manual-common-tasks:maintaining open source license compliance during your product's lifecycle`"
205section in the Yocto Project Development Tasks Manual.
206
207**Q:** How do I disable the cursor on my touchscreen device?
208
209**A:** You need to create a form factor file as described in the
210":ref:`bsp-filelayout-misc-recipes`" section in
211the Yocto Project Board Support Packages (BSP) Developer's Guide. Set
212the ``HAVE_TOUCHSCREEN`` variable equal to one as follows:
213::
214
215 HAVE_TOUCHSCREEN=1
216
217**Q:** How do I make sure connected network interfaces are brought up by
218default?
219
220**A:** The default interfaces file provided by the netbase recipe does
221not automatically bring up network interfaces. Therefore, you will need
222to add a BSP-specific netbase that includes an interfaces file. See the
223":ref:`bsp-filelayout-misc-recipes`" section in
224the Yocto Project Board Support Packages (BSP) Developer's Guide for
225information on creating these types of miscellaneous recipe files.
226
227For example, add the following files to your layer: ::
228
229 meta-MACHINE/recipes-bsp/netbase/netbase/MACHINE/interfaces
230 meta-MACHINE/recipes-bsp/netbase/netbase_5.0.bbappend
231
232**Q:** How do I create images with more free space?
233
234**A:** By default, the OpenEmbedded build system creates images that are
2351.3 times the size of the populated root filesystem. To affect the image
236size, you need to set various configurations:
237
238- *Image Size:* The OpenEmbedded build system uses the
239 :term:`IMAGE_ROOTFS_SIZE` variable to define
240 the size of the image in Kbytes. The build system determines the size
241 by taking into account the initial root filesystem size before any
242 modifications such as requested size for the image and any requested
243 additional free disk space to be added to the image.
244
245- *Overhead:* Use the
246 :term:`IMAGE_OVERHEAD_FACTOR` variable
247 to define the multiplier that the build system applies to the initial
248 image size, which is 1.3 by default.
249
250- *Additional Free Space:* Use the
251 :term:`IMAGE_ROOTFS_EXTRA_SPACE`
252 variable to add additional free space to the image. The build system
253 adds this space to the image after it determines its
254 ``IMAGE_ROOTFS_SIZE``.
255
256**Q:** Why don't you support directories with spaces in the pathnames?
257
258**A:** The Yocto Project team has tried to do this before but too many
259of the tools the OpenEmbedded build system depends on, such as
260``autoconf``, break when they find spaces in pathnames. Until that
261situation changes, the team will not support spaces in pathnames.
262
263**Q:** How do I use an external toolchain?
264
265**A:** The toolchain configuration is very flexible and customizable. It
266is primarily controlled with the ``TCMODE`` variable. This variable
267controls which ``tcmode-*.inc`` file to include from the
268``meta/conf/distro/include`` directory within the :term:`Source Directory`.
269
270The default value of ``TCMODE`` is "default", which tells the
271OpenEmbedded build system to use its internally built toolchain (i.e.
272``tcmode-default.inc``). However, other patterns are accepted. In
273particular, "external-\*" refers to external toolchains. One example is
274the Sourcery G++ Toolchain. The support for this toolchain resides in
275the separate ``meta-sourcery`` layer at
276http://github.com/MentorEmbedded/meta-sourcery/.
277
278In addition to the toolchain configuration, you also need a
279corresponding toolchain recipe file. This recipe file needs to package
280up any pre-built objects in the toolchain such as ``libgcc``,
281``libstdcc++``, any locales, and ``libc``.
282
283**Q:** How does the OpenEmbedded build system obtain source code and
284will it work behind my firewall or proxy server?
285
286**A:** The way the build system obtains source code is highly
287configurable. You can setup the build system to get source code in most
288environments if HTTP transport is available.
289
290When the build system searches for source code, it first tries the local
291download directory. If that location fails, Poky tries
292:term:`PREMIRRORS`, the upstream source, and then
293:term:`MIRRORS` in that order.
294
295Assuming your distribution is "poky", the OpenEmbedded build system uses
296the Yocto Project source ``PREMIRRORS`` by default for SCM-based
297sources, upstreams for normal tarballs, and then falls back to a number
298of other mirrors including the Yocto Project source mirror if those
299fail.
300
301As an example, you could add a specific server for the build system to
302attempt before any others by adding something like the following to the
303``local.conf`` configuration file: ::
304
305 PREMIRRORS_prepend = "\
306 git://.*/.* http://www.yoctoproject.org/sources/ \n \
307 ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
308 http://.*/.* http://www.yoctoproject.org/sources/ \n \
309 https://.*/.* http://www.yoctoproject.org/sources/ \n"
310
311These changes cause the build system to intercept Git, FTP, HTTP, and
312HTTPS requests and direct them to the ``http://`` sources mirror. You
313can use ``file://`` URLs to point to local directories or network shares
314as well.
315
316Aside from the previous technique, these options also exist:
317::
318
319 BB_NO_NETWORK = "1"
320
321This statement tells BitBake to issue an error
322instead of trying to access the Internet. This technique is useful if
323you want to ensure code builds only from local sources.
324
325Here is another technique:
326::
327
328 BB_FETCH_PREMIRRORONLY = "1"
329
330This statement
331limits the build system to pulling source from the ``PREMIRRORS`` only.
332Again, this technique is useful for reproducing builds.
333
334Here is another technique:
335::
336
337 BB_GENERATE_MIRROR_TARBALLS = "1"
338
339This
340statement tells the build system to generate mirror tarballs. This
341technique is useful if you want to create a mirror server. If not,
342however, the technique can simply waste time during the build.
343
344Finally, consider an example where you are behind an HTTP-only firewall.
345You could make the following changes to the ``local.conf`` configuration
346file as long as the ``PREMIRRORS`` server is current: ::
347
348 PREMIRRORS_prepend = "\
349 ftp://.*/.* http://www.yoctoproject.org/sources/ \n \
350 http://.*/.* http://www.yoctoproject.org/sources/ \n \
351 https://.*/.* http://www.yoctoproject.org/sources/ \n"
352 BB_FETCH_PREMIRRORONLY = "1"
353
354These changes would cause the build system to successfully fetch source
355over HTTP and any network accesses to anything other than the
356``PREMIRRORS`` would fail.
357
358The build system also honors the standard shell environment variables
359``http_proxy``, ``ftp_proxy``, ``https_proxy``, and ``all_proxy`` to
360redirect requests through proxy servers.
361
362.. note::
363
364 You can find more information on the
365 ":yocto_wiki:`Working Behind a Network Proxy </wiki/Working_Behind_a_Network_Proxy>`"
366 Wiki page.
367
368**Q:** Can I get rid of build output so I can start over?
369
370**A:** Yes - you can easily do this. When you use BitBake to build an
371image, all the build output goes into the directory created when you run
372the build environment setup script (i.e.
373````` <#structure-core-script>`__). By default, this :term:`Build Directory`
374is named ``build`` but can be named
375anything you want.
376
377Within the Build Directory, is the ``tmp`` directory. To remove all the
378build output yet preserve any source code or downloaded files from
379previous builds, simply remove the ``tmp`` directory.
380
381**Q:** Why do ``${bindir}`` and ``${libdir}`` have strange values for
382``-native`` recipes?
383
384**A:** Executables and libraries might need to be used from a directory
385other than the directory into which they were initially installed.
386Complicating this situation is the fact that sometimes these executables
387and libraries are compiled with the expectation of being run from that
388initial installation target directory. If this is the case, moving them
389causes problems.
390
391This scenario is a fundamental problem for package maintainers of
392mainstream Linux distributions as well as for the OpenEmbedded build
393system. As such, a well-established solution exists. Makefiles,
394Autotools configuration scripts, and other build systems are expected to
395respect environment variables such as ``bindir``, ``libdir``, and
396``sysconfdir`` that indicate where executables, libraries, and data
397reside when a program is actually run. They are also expected to respect
398a ``DESTDIR`` environment variable, which is prepended to all the other
399variables when the build system actually installs the files. It is
400understood that the program does not actually run from within
401``DESTDIR``.
402
403When the OpenEmbedded build system uses a recipe to build a
404target-architecture program (i.e. one that is intended for inclusion on
405the image being built), that program eventually runs from the root file
406system of that image. Thus, the build system provides a value of
407"/usr/bin" for ``bindir``, a value of "/usr/lib" for ``libdir``, and so
408forth.
409
410Meanwhile, ``DESTDIR`` is a path within the :term:`Build Directory`.
411However, when the recipe builds a
412native program (i.e. one that is intended to run on the build machine),
413that program is never installed directly to the build machine's root
414file system. Consequently, the build system uses paths within the Build
415Directory for ``DESTDIR``, ``bindir`` and related variables. To better
416understand this, consider the following two paths where the first is
417relatively normal and the second is not: ::
418
419 /home/maxtothemax/poky-bootchart2/build/tmp/work/i586-poky-linux/zlib/
420 1.2.8-r0/sysroot-destdir/usr/bin
421
422 /home/maxtothemax/poky-bootchart2/build/tmp/work/x86_64-linux/
423 zlib-native/1.2.8-r0/sysroot-destdir/home/maxtothemax/poky-bootchart2/
424 build/tmp/sysroots/x86_64-linux/usr/bin
425
426.. note::
427
428 Due to these lengthy examples, the paths are artificially broken
429 across lines for readability.
430
431Even if the paths look unusual,
432they both are correct - the first for a target and the second for a
433native recipe. These paths are a consequence of the ``DESTDIR``
434mechanism and while they appear strange, they are correct and in
435practice very effective.
436
437**Q:** The files provided by my ``*-native`` recipe do not appear to be
438available to other recipes. Files are missing from the native sysroot,
439my recipe is installing to the wrong place, or I am getting permissions
440errors during the do_install task in my recipe! What is wrong?
441
442**A:** This situation results when a build system does not recognize the
443environment variables supplied to it by :term:`BitBake`. The
444incident that prompted this FAQ entry involved a Makefile that used an
445environment variable named ``BINDIR`` instead of the more standard
446variable ``bindir``. The makefile's hardcoded default value of
447"/usr/bin" worked most of the time, but not for the recipe's ``-native``
448variant. For another example, permissions errors might be caused by a
449Makefile that ignores ``DESTDIR`` or uses a different name for that
450environment variable. Check the the build system to see if these kinds
451of issues exist.