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I see lots of 404 responses for files when the OpenEmbedded

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build system is trying to download sources.

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Is something wrong?

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</para>

</question>

<para>

Nothing is wrong.

The OpenEmbedded build system checks any configured source mirrors before downloading

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from the upstream sources.

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The build system does this searching for both source archives and

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pre-checked out versions of SCM-managed software.

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These checks help in large installations because it can reduce load on the SCM servers

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themselves.

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The address above is one of the default mirrors configured into the

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build system.

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Consequently, if an upstream source disappears, the team

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can place sources there so builds continue to work.

</para>

</answer>

</qandaentry>

<para>

I have machine-specific data in a package for one machine only but the package is

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being marked as machine-specific in all cases, how do I prevent this?

</para>

</question>

<para>

Set <filename><link linkend='var-SRC_URI_OVERRIDES_PACKAGE_ARCH'>SRC_URI_OVERRIDES_PACKAGE_ARCH</link>

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</filename> = "0" in the <filename>.bb</filename> file but make sure the package is

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manually marked as

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machine-specific for the case that needs it.

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The code that handles

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<filename>SRC_URI_OVERRIDES_PACKAGE_ARCH</filename> is in

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the <filename>meta/classes/base.bbclass</filename> file.

</para>

</answer>

</qandaentry>

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I'm behind a firewall and need to use a proxy server. How do I do that?

</para>

</question>

<para>

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Most source fetching by the OpenEmbedded build system is done

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by <filename>wget</filename> and you therefore need to specify

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the proxy settings in a <filename>.wgetrc</filename> file,

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which can be in your home directory if you are a single user

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or can be in <filename>/usr/local/etc/wgetrc</filename> as

a global user file.

</para>

<para>

Following is the applicable code for setting various proxy

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types in the <filename>.wgetrc</filename> file.

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By default, these settings are disabled with comments.

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To use them, remove the comments:

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# You can set the default proxies for Wget to use for http, https, and ftp.

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# They will override the value in the environment.

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#https_proxy = http://proxy.yoyodyne.com:18023/

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#http_proxy = http://proxy.yoyodyne.com:18023/

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#ftp_proxy = http://proxy.yoyodyne.com:18023/

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# If you do not want to use proxy at all, set this to off.

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#use_proxy = on

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</literallayout>

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The Yocto Project also includes a

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<filename>meta-poky/conf/site.conf.sample</filename> file that

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shows how to configure CVS and Git proxy servers if needed.

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For more information on setting up various proxy types and

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configuring proxy servers, see the

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"<ulink url='&YOCTO_WIKI_URL;/wiki/Working_Behind_a_Network_Proxy'>Working Behind a Network Proxy</ulink>"

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Wiki page.

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</para>

</answer>

</qandaentry>

<para>

What’s the difference between <replaceable>target</replaceable> and <replaceable>target</replaceable><filename>-native</filename>?

</para>

</question>

<para>

The <filename>*-native</filename> targets are designed to run on the system

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being used for the build.

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These are usually tools that are needed to assist the build in some way such as

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<filename>quilt-native</filename>, which is used to apply patches.

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The non-native version is the one that runs on the target device.

</para>

</answer>

</qandaentry>

<para>

I'm seeing random build failures. Help?!

</para>

</question>

<para>

If the same build is failing in totally different and random

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ways, the most likely explanation is:

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<listitem><para>The hardware you are running the build on

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has some problem.</para></listitem>

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<listitem><para>You are running the build under

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virtualization, in which case the virtualization

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probably has bugs.</para></listitem>

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</itemizedlist>

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The OpenEmbedded build system processes a massive amount of

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data that causes lots of network, disk and CPU activity and

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is sensitive to even single-bit failures in any of these areas.

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True random failures have always been traced back to hardware

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or virtualization issues.

</para>

</answer>

</qandaentry>

<para>

When I try to build a native recipe, the build fails with <filename>iconv.h</filename> problems.

</para>

</question>

<para>

If you get an error message that indicates GNU

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<filename>libiconv</filename> is not in use but

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<filename>iconv.h</filename> has been included from

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<filename>libiconv</filename>, you need to check to see if

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you have a previously installed version of the header file

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in <filename>/usr/local/include</filename>.

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#error GNU libiconv not in use but included iconv.h is from libiconv

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</literallayout>

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If you find a previously installed file, you should either

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uninstall it or temporarily rename it and try the build again.

</para>

<para>

This issue is just a single manifestation of "system

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leakage" issues caused when the OpenEmbedded build system

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finds and uses previously installed files during a native

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build.

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This type of issue might not be limited to

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<filename>iconv.h</filename>.

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Be sure that leakage cannot occur from

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<filename>/usr/local/include</filename> and

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<filename>/opt</filename> locations.

</para>

</answer>

</qandaentry>

<para>

What do we need to ship for license compliance?

</para>

</question>

<para>

This is a difficult question and you need to consult your lawyer

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for the answer for your specific case.

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It is worth bearing in mind that for GPL compliance, there needs

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to be enough information shipped to allow someone else to

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rebuild and produce the same end result you are shipping.

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This means sharing the source code, any patches applied to it,

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and also any configuration information about how that package

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was configured and built.

</para>

<para>

You can find more information on licensing in the

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"<ulink url='&YOCTO_DOCS_OM_URL;#licensing'>Licensing</ulink>"

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section in the Yocto Project Overview and Concepts Manual

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and also in the

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"<ulink url='&YOCTO_DOCS_DEV_URL;#maintaining-open-source-license-compliance-during-your-products-lifecycle'>Maintaining Open Source License Compliance During Your Product's Lifecycle</ulink>"

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section in the Yocto Project Development Tasks Manual.

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</para>

</answer>

</qandaentry>

<para>

How do I disable the cursor on my touchscreen device?

</para>

</question>

<para>

You need to create a form factor file as described in the

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"<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-filelayout-misc-recipes'>Miscellaneous BSP-Specific Recipe Files</ulink>"

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section in the Yocto Project Board Support Packages (BSP)

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Developer's Guide.

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Set the <filename>HAVE_TOUCHSCREEN</filename> variable equal to

one as follows:

HAVE_TOUCHSCREEN=1

</literallayout>

</para>

</answer>

</qandaentry>

<para>

How do I make sure connected network interfaces are brought up by default?

</para>

</question>

<para>

The default interfaces file provided by the netbase recipe does not

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automatically bring up network interfaces.

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Therefore, you will need to add a BSP-specific netbase that includes an interfaces

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file.

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See the "<ulink url='&YOCTO_DOCS_BSP_URL;#bsp-filelayout-misc-recipes'>Miscellaneous BSP-Specific Recipe Files</ulink>"

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section in the Yocto Project Board Support Packages (BSP)

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Developer's Guide for information on creating these types of

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miscellaneous recipe files.

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</para>

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<para>

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For example, add the following files to your layer:

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meta-MACHINE/recipes-bsp/netbase/netbase/MACHINE/interfaces

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meta-MACHINE/recipes-bsp/netbase/netbase_5.0.bbappend

</literallayout>

</para>

</answer>

</qandaentry>

<para>

How do I create images with more free space?

</para>

</question>

<para>

By default, the OpenEmbedded build system creates images

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that are 1.3 times the size of the populated root filesystem.

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To affect the image size, you need to set various

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configurations:

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<listitem><para><emphasis>Image Size:</emphasis>

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The OpenEmbedded build system uses the

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variable to define the size of the image in Kbytes.

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The build system determines the size by taking into

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account the initial root filesystem size before any

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modifications such as requested size for the image and

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any requested additional free disk space to be

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added to the image.</para></listitem>

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<listitem><para><emphasis>Overhead:</emphasis>

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Use the

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variable to define the multiplier that the build system

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applies to the initial image size, which is 1.3 by

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default.</para></listitem>

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<listitem><para><emphasis>Additional Free Space:</emphasis>

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Use the

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variable to add additional free space to the image.

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The build system adds this space to the image after

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it determines its

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<filename>IMAGE_ROOTFS_SIZE</filename>.

</para></listitem>

</itemizedlist>

</para>

</answer>

</qandaentry>

<para>

Why don't you support directories with spaces in the pathnames?

</para>

</question>

<para>

The Yocto Project team has tried to do this before but too

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many of the tools the OpenEmbedded build system depends on,

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such as <filename>autoconf</filename>, break when they find

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spaces in pathnames.

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Until that situation changes, the team will not support spaces

in pathnames.

</para>

</answer>

</qandaentry>

<para>

How do I use an external toolchain?

</para>

</question>

<para>

The toolchain configuration is very flexible and customizable.

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It is primarily controlled with the

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<filename><link linkend='var-TCMODE'>TCMODE</link></filename>

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variable.

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This variable controls which <filename>tcmode-*.inc</filename>

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file to include from the

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<filename>meta/conf/distro/include</filename> directory within

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the

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</para>

<para>

The default value of <filename>TCMODE</filename> is "default",

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which tells the OpenEmbedded build system to use its internally

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built toolchain (i.e. <filename>tcmode-default.inc</filename>).

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However, other patterns are accepted.

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In particular, "external-*" refers to external toolchains.

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One example is the Sourcery G++ Toolchain.

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The support for this toolchain resides in the separate

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<filename>meta-sourcery</filename> layer at

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<ulink url='http://github.com/MentorEmbedded/meta-sourcery/'></ulink>.

</para>

<para>

In addition to the toolchain configuration, you also need a

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corresponding toolchain recipe file.

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This recipe file needs to package up any pre-built objects in

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the toolchain such as <filename>libgcc</filename>,

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<filename>libstdcc++</filename>, any locales, and

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<filename>libc</filename>.

</para>

</answer>

</qandaentry>

How does the OpenEmbedded build system obtain source code and

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will it work behind my firewall or proxy server?

</para>

</question>

<para>

The way the build system obtains source code is highly

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configurable.

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You can setup the build system to get source code in most

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environments if HTTP transport is available.

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</para>

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<para>

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When the build system searches for source code, it first

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tries the local download directory.

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If that location fails, Poky tries

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the upstream source, and then

in that order.

</para>

<para>

Assuming your distribution is "poky", the OpenEmbedded build

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system uses the Yocto Project source

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<filename>PREMIRRORS</filename> by default for SCM-based

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sources, upstreams for normal tarballs, and then falls back

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to a number of other mirrors including the Yocto Project

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source mirror if those fail.

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</para>

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<para>

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As an example, you could add a specific server for the

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build system to attempt before any others by adding something

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like the following to the <filename>local.conf</filename>

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configuration file:

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PREMIRRORS_prepend = "\

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git://.*/.* http://www.yoctoproject.org/sources/ \n \

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ftp://.*/.* http://www.yoctoproject.org/sources/ \n \

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http://.*/.* http://www.yoctoproject.org/sources/ \n \

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https://.*/.* http://www.yoctoproject.org/sources/ \n"

</literallayout>

</para>

<para>

These changes cause the build system to intercept Git, FTP,

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HTTP, and HTTPS requests and direct them to the

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<filename>http://</filename> sources mirror.

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You can use <filename>file://</filename> URLs to point to

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local directories or network shares as well.

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</para>

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<para>

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Aside from the previous technique, these options also exist:

BB_NO_NETWORK = "1"

</literallayout>

This statement tells BitBake to issue an error instead of

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trying to access the Internet.

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This technique is useful if you want to ensure code builds

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only from local sources.

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</para>

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<para>

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Here is another technique:

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BB_FETCH_PREMIRRORONLY = "1"

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</literallayout>

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This statement limits the build system to pulling source

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from the <filename>PREMIRRORS</filename> only.

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Again, this technique is useful for reproducing builds.

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</para>

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<para>

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Here is another technique:

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BB_GENERATE_MIRROR_TARBALLS = "1"

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</literallayout>

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This statement tells the build system to generate mirror

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tarballs.

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This technique is useful if you want to create a mirror server.

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If not, however, the technique can simply waste time during

the build.

</para>

<para>

Finally, consider an example where you are behind an

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HTTP-only firewall.

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You could make the following changes to the

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<filename>local.conf</filename> configuration file as long as

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the <filename>PREMIRRORS</filename> server is current:

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PREMIRRORS_prepend = "\

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ftp://.*/.* http://www.yoctoproject.org/sources/ \n \

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http://.*/.* http://www.yoctoproject.org/sources/ \n \

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https://.*/.* http://www.yoctoproject.org/sources/ \n"

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BB_FETCH_PREMIRRORONLY = "1"

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</literallayout>

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These changes would cause the build system to successfully

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fetch source over HTTP and any network accesses to anything

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other than the <filename>PREMIRRORS</filename> would fail.

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</para>

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<para>

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The build system also honors the standard shell environment

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variables <filename>http_proxy</filename>,

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<filename>ftp_proxy</filename>,

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<filename>https_proxy</filename>, and

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<filename>all_proxy</filename> to redirect requests through

proxy servers.

</para>

<note>

You can find more information on the

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"<ulink url='&YOCTO_WIKI_URL;/wiki/Working_Behind_a_Network_Proxy'>Working Behind a Network Proxy</ulink>"

Wiki page.

</note>

</answer>

</qandaentry>

<para>

Can I get rid of build output so I can start over?

</para>

</question>

<para>

Yes - you can easily do this.

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When you use BitBake to build an image, all the build output

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goes into the directory created when you run the

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build environment setup script (i.e.

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is named <filename>build</filename> but can be named

anything you want.

</para>

<para>

Within the Build Directory, is the <filename>tmp</filename>

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directory.

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To remove all the build output yet preserve any source code or

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downloaded files from previous builds, simply remove the

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<filename>tmp</filename> directory.

</para>

</answer>

</qandaentry>

<para>

Why do <filename>${bindir}</filename> and <filename>${libdir}</filename> have strange values for <filename>-native</filename> recipes?

</para>

</question>

<para>

Executables and libraries might need to be used from a

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directory other than the directory into which they were

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initially installed.

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Complicating this situation is the fact that sometimes these

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executables and libraries are compiled with the expectation

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of being run from that initial installation target directory.

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If this is the case, moving them causes problems.

</para>

<para>

This scenario is a fundamental problem for package maintainers

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of mainstream Linux distributions as well as for the

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OpenEmbedded build system.

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As such, a well-established solution exists.

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Makefiles, Autotools configuration scripts, and other build

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systems are expected to respect environment variables such as

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<filename>bindir</filename>, <filename>libdir</filename>,

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and <filename>sysconfdir</filename> that indicate where

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executables, libraries, and data reside when a program is

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actually run.

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They are also expected to respect a

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<filename>DESTDIR</filename> environment variable, which is

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prepended to all the other variables when the build system

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actually installs the files.

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It is understood that the program does not actually run from

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within <filename>DESTDIR</filename>.

</para>

<para>

When the OpenEmbedded build system uses a recipe to build a

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target-architecture program (i.e. one that is intended for

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inclusion on the image being built), that program eventually

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runs from the root file system of that image.

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Thus, the build system provides a value of "/usr/bin" for

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<filename>bindir</filename>, a value of "/usr/lib" for

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<filename>libdir</filename>, and so forth.

</para>

<para>

Meanwhile, <filename>DESTDIR</filename> is a path within the

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However, when the recipe builds a native program (i.e. one

771

that is intended to run on the build machine), that program

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is never installed directly to the build machine's root

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file system.

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Consequently, the build system uses paths within the Build

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Directory for <filename>DESTDIR</filename>,

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<filename>bindir</filename> and related variables.

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To better understand this, consider the following two paths

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where the first is relatively normal and the second is not:

779

<note>

780

Due to these lengthy examples, the paths are artificially

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broken across lines for readability.

782

</note>

783

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/home/maxtothemax/poky-bootchart2/build/tmp/work/i586-poky-linux/zlib/

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1.2.8-r0/sysroot-destdir/usr/bin

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/home/maxtothemax/poky-bootchart2/build/tmp/work/x86_64-linux/

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zlib-native/1.2.8-r0/sysroot-destdir/home/maxtothemax/poky-bootchart2/

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build/tmp/sysroots/x86_64-linux/usr/bin

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</literallayout>

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Even if the paths look unusual, they both are correct -

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the first for a target and the second for a native recipe.

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These paths are a consequence of the

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<filename>DESTDIR</filename> mechanism and while they

795

appear strange, they are correct and in practice very effective.

</para>

</answer>

</qandaentry>

<para>

Patrick Williams

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The files provided by my <filename>*-native</filename> recipe do

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not appear to be available to other recipes.

805

Files are missing from the native sysroot, my recipe is

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installing to the wrong place, or I am getting permissions

807

errors during the do_install task in my recipe! What is wrong?

</para>

</question>

<para>

This situation results when a build system does

813

not recognize the environment variables supplied to it by

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Patrick Williams