YOCTO PROJECT

Yocto Project

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Child Pages

  • Bitbake
  • Building Yocto
  • Developing And Remote Debugging Python App On Yocto Linux Build
  • Device Trees
  • How To Add A Custom App To A Yocto Build
  • Premade Recipes
  • Using CMake With The SDK
  • Yocto Recipes
  • Overview

    The Yocto Project, or more commonly just called Yocto, is a build system used to create custom Linux distributions for embedded systems.

    The logo for the Yocto project.

    The logo for the Yocto project.

    Quick Start

    This is a Yocto “Quick Start”, aimed to get you familiar with the basics of the Yocto and building a embedded Linux image in no time!

    This quick start has been tested with Ubuntu 16.04 64-bit, running in VMWare on a Windows host (the free VirtualBox VM should also work fine).

    Yocto has it’s own quick start guide at http://www.yoctoproject.org/docs/2.2.1/yocto-project-qs/yocto-project-qs.html. However, I have has problems with this, including errors such as:

    E: Unable to locate package pip3
    E: Unable to locate package pexpect
    

    Install Prerequisites

    Run the following bash command:

    $ sudo apt-get install gawk wget git-core diffstat unzip texinfo gcc-multilib build-essential chrpath socat cpio python python3 python-pip libsdl1.2-dev xterm

    Clone Yocto’s poky Repository

    poky is a Yocto project release. As of April 2017, this is the most recent release. Run the following command, which should clone poky into ~/poky/.

    $ git clone git://git.yoctoproject.org/poky

    Checkout The Correct Branch Of poky

    Now change into the poky directory:

    $ cd poky/

    Switch to the morty branch:

    $ git checkout morty

    (with new versions of git, this will automatically set it up to track origin/morty).

    Initialise Build Environment

    Before you can start a Linux build, you need to initialise the Yocto build environment. This can be done with the following command:

    $ source oe-init-build-env

    After running this command, you should of automatically been moved into the poky/build/ directory.

    This command needs to be re-run everytime your environment variables get reset (e.g. everytime you login).

    Build Linux

    We’re almost at Linux building time! We won’t touch any of the config files for now, and just build Linux using Yocto’s default settings. Run the following command (from the poky/build/ directory):

    $ bitbake core-image-sato

    Now go grab a coffee. Or better yet, take your family out to a restaurant for a nice meal. This is going to TAKE A WHILE.

    An embedded Linux build in progress (using Yocto), note the CPU usage!

    An embedded Linux build in progress (using Yocto), note the CPU usage!

    Make sure your computer is not set to go to sleep/shutdown after 1-2 hours of activity, otherwise you might find the build won’t complete!

    Yocto will calculate all dependencies, download them, and compile! (make sure you have an o.k. internet connection).

    You can safely ignore (usually) most of the orange “Failed to fetch URL…” warnings that pop-up as the build progresses, as Yocto can attempt to download them from other sources.

    After the build was complete, Yocto had used about 35GB of hard drive memory. The output build images should be in poky/build/tmp/deploy/images/. You can now test out the Linux image you just built by running it in QEMU:

    $ runqemu qemux86

    This should load up a separate window, and display a GUI of the Linux image you just built.

    Running the finished Yocto build in QEMU (an emulator).

    Running the finished Yocto build in QEMU (an emulator).

    The Project Configuration File

    The main configuration for a Yocto project is located at poky/build/conf/local.conf.

    Moving The Entire Yocto Project Directory Somewhere Else

    Moving the entire Yocto project directory isn’t as straightforward as you might think (e.g. moving or renaming the poky folder). Because Yocto stores a small but non-zero amount of information in the project using absolute paths (gasp!), moving/renaming this folder will break a build (assuming a build has already been completed at least once, if not, you’re o.k.!).

    You will probably receive an error message along the lines of:

    Oh no! I have to rebuild? But that took hours! Luckily, you can fix this without having to do a complete rebuild. Upon receiving this error, open up the poky/build/tmp/saved_tmpdir file in a text editor, and update the path to the new location (the path should be the only thing in this file).

    You should now be able to run bitbake … without any errors, and without having to restart the build from scratch.

    Disabling sanity Checks

    Although not recommended, sometimes it is necessary to disable the sanity checks. This can be done by commenting out the out the INHERIT += “sanity” line from the file meta/conf/sanity.conf, so it looks like the following:

    # Sanity checks for common user misconfigurations
    #
    # See sanity.bbclass
    #
    # Expert users can confirm their sanity with "touch conf/sanity.conf"
    BB_MIN_VERSION = "1.31.2"
    
    SANITY_ABIFILE = "${TMPDIR}/abi_version"
    
    SANITY_VERSION ?= "1"
    LOCALCONF_VERSION  ?= "1"
    LAYER_CONF_VERSION ?= "7"
    SITE_CONF_VERSION  ?= "1"
    
    #INHERIT += "sanity"

    This will disable all sanity checks, including:

    • Do not use Bitbake as root
    • Error, TMPDIR has changed location
    • The TMPDIR: can’t be located on nfs.

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