# Introduction

## Introduction

This manual provides reference information for the current release of the Yocto Project. The Yocto Project is an open-source collaboration project focused on embedded Linux developers. Amongst other things, the Yocto Project uses the OpenEmbedded build system, which is based on the Poky project, to construct complete Linux images. You can find complete introductory and getting started information on the Yocto Project by reading the Yocto Project Quick Start. For task-based information using the Yocto Project, see the Yocto Project Development Manual and the Yocto Project Linux Kernel Development Manual. For Board Support Package (BSP) structure information, see the Yocto Project Board Support Package (BSP) Developer's Guide. You can also find lots of Yocto Project information on the Yocto Project website.

## Documentation Overview

This reference manual consists of the following:

- Using the Yocto Project: Provides an overview of the components that make up the Yocto Project followed by information about debugging images created in the Yocto Project.

- Technical Details: Describes fundamental Yocto Project components as well as an explanation behind how the Yocto Project uses shared state (sstate) cache to speed build time.

- Directory Structure: Describes the Source Directory created either by unpacking a released Yocto Project tarball on your host development system, or by cloning the upstream Poky Git repository.

- BitBake: Provides an overview of the BitBake tool and its role within the Yocto Project.

- Classes: Describes the classes used in the Yocto Project.

- Images: Describes the standard images that the Yocto Project supports.

- Features: Describes mechanisms for creating distribution, machine, and image features during the build process using the OpenEmbedded build system.

- Variables Glossary: Presents most variables used by the OpenEmbedded build system, which uses BitBake. Entries describe the function of the variable and how to apply them.

- Variable Context: Provides variable locality or context.

- FAQ: Provides answers for commonly asked questions in the Yocto Project development environment.

- Contributing to the Yocto Project: Provides guidance on how you can contribute back to the Yocto Project.

## System Requirements

For general Yocto Project system requirements, see the "What You Need and How You Get It" section in the Yocto Project Quick Start. The remainder of this section provides details on system requirements not covered in the Yocto Project Quick Start.

### Supported Linux Distributions

Currently, the Yocto Project is supported on the following distributions:

Yocto Project releases are tested against the stable Linux distributions in the following list. The Yocto Project should work on other distributions but validation is not performed against them.

In particular, the Yocto Project does not support and currently has no plans to support rolling-releases or development distributions due to their constantly changing nature. We welcome patches and bug reports, but keep in mind that our priority is on the supported platforms listed below.

Refer to OE and Your Distro and Required Software for information for information about dependencies and requirements. If you encounter problems, please go to Yocto Project Bugzilla and submit a bug. We are interested in hearing about your experience.

- Ubuntu 12.04 (LTS)

- Ubuntu 12.10

- Ubuntu 13.04

- Fedora release 18 (Spherical Cow)

- Fedora release 19 (Schrödinger's Cat)

- CentOS release 6.4

- Debian GNU/Linux 6.0.7 (Squeeze)

- Debian GNU/Linux 7.0 (Wheezy)

- Debian GNU/Linux 7.1 (Wheezy)

- openSUSE 12.2

- openSUSE 12.3

While the Yocto Project Team attempts to ensure all Yocto Project releases are one hundred percent compatible with each officially supported Linux distribution, instances might exist where you encounter a problem while using the Yocto Project on a specific distribution. For example, the CentOS 6.4 distribution does not include the Gtk+ 2.20.0 and PyGtk 2.21.0 (or higher) packages, which are required to run Hob.

### Required Packages for the Host Development System

The list of packages you need on the host development system can be large when covering all build scenarios using the Yocto Project. This section provides required packages according to Linux distribution and function.

#### Ubuntu and Debian

The following list shows the required packages by function given a supported Ubuntu or Debian Linux distribution:

- Essentials: Packages needed to build an image on a headless system:

           $ sudo apt-get install &UBUNTU_HOST_PACKAGES_ESSENTIAL;

- Graphical Extras: Packages recommended if the host system has graphics support:

           $ sudo apt-get install libsdl1.2-dev xterm

- Documentation: Packages needed if you are going to build out the Yocto Project documentation manuals:

           $ sudo apt-get install make xsltproc docbook-utils fop dblatex xmlto

- ADT Installer Extras: Packages needed if you are going to be using the Application Development Toolkit (ADT) Installer:

           $ sudo apt-get install autoconf automake libtool libglib2.0-dev

#### Fedora Packages

The following list shows the required packages by function given a supported Fedora Linux distribution:

- Essentials: Packages needed to build an image for a headless system:

           $ sudo yum install &FEDORA_HOST_PACKAGES_ESSENTIAL;

- Graphical Extras: Packages recommended if the host system has graphics support:

           $ sudo yum install SDL-devel xterm

- Documentation: Packages needed if you are going to build out the Yocto Project documentation manuals:

           $ sudo yum install make docbook-style-dsssl docbook-style-xsl \
           docbook-dtds docbook-utils fop libxslt dblatex xmlto

- ADT Installer Extras: Packages needed if you are going to be using the Application Development Toolkit (ADT) Installer:

           $ sudo yum install autoconf automake libtool glib2-devel

#### OpenSUSE Packages

The following list shows the required packages by function given a supported OpenSUSE Linux distribution:

- Essentials: Packages needed to build an image for a headless system:

           $ sudo zypper install &OPENSUSE_HOST_PACKAGES_ESSENTIAL;

- Graphical Extras: Packages recommended if the host system has graphics support:

           $ sudo zypper install libSDL-devel xterm

- Documentation: Packages needed if you are going to build out the Yocto Project documentation manuals:

           $ sudo zypper install make fop xsltproc dblatex xmlto

- ADT Installer Extras: Packages needed if you are going to be using the Application Development Toolkit (ADT) Installer:

           $ sudo zypper install autoconf automake libtool glib2-devel

#### CentOS Packages

The following list shows the required packages by function given a supported CentOS Linux distribution:

Depending on the CentOS version you are using, other requirements and dependencies might exist. For details, you should look at the CentOS sections on the Poky/GettingStarted/Dependencies wiki page.

- Essentials: Packages needed to build an image for a headless system:

           $ sudo yum install &CENTOS_HOST_PACKAGES_ESSENTIAL;

- Graphical Extras: Packages recommended if the host system has graphics support:

           $ sudo yum install SDL-devel xterm

- Documentation: Packages needed if you are going to build out the Yocto Project documentation manuals:

           $ sudo yum install make docbook-style-dsssl docbook-style-xsl \
           docbook-dtds docbook-utils fop libxslt dblatex xmlto

- ADT Installer Extras: Packages needed if you are going to be using the Application Development Toolkit (ADT) Installer:

           $ sudo yum install autoconf automake libtool glib2-devel

### Required Git, tar, and Python Versions

In order to use the build system, your host development system must meet the following version requirements for Git, tar, and Python:

- Git 1.7.5 or greater

- tar 1.24 or greater

- Python 2.7.3 or greater not including Python 3.x, which is not supported.

If your host development system does not meet all these requirements, you can resolve this by either downloading a pre-built tarball containing these tools, or building such a tarball on another system. Regardless of the method, once you have the tarball you simply install it somewhere on you system, such as a directory in your home directory, and then source the environment script provided, which adds the tools into `PATH` and sets any other environment variables required to run the tools. Doing so gives you working versions of Git, tar, Python and `chrpath`.

If downloading a pre-built tarball, locate the `*.sh` at .

If building your own tarball, do so using this command:

         $ bitbake buildtools-tarball

The `SDKMACHINE` variable determines whether you build tools for a 32-bit or 64-bit system.

Once the build completes, you can find the file that installs the the tools in the `tmp/deploy/sdk` subdirectory of the Build Directory. The file used to install the tarball has the string "buildtools" in the name.

After you have either built the tarball or downloaded it, you need to install it. Install the tools by executing the `*.sh` file. During execution, a prompt appears that allows you to choose the installation directory. For example, you could choose the following:

         /home/your-username/sdk

The final step before you can actually use the tools is to source the tools environment with a command like the following:

         $ source /home/your-username/sdk/environment-setup-i586-poky-linux

Of course, you need to supply your installation directory and be sure to use the right file (i.e. i585 or x86-64).

## Obtaining the Yocto Project

The Yocto Project development team makes the Yocto Project available through a number of methods:

- Releases: Stable, tested releases are available through .

- Nightly Builds: These releases are available at . These builds include Yocto Project releases, meta-toolchain tarball installation scripts, and experimental builds.

- Yocto Project Website: You can find releases of the Yocto Project and supported BSPs at the Yocto Project website. Along with these downloads, you can find lots of other information at this site.

## Development Checkouts

Development using the Yocto Project requires a local Source Directory. You can set up the Source Directory by downloading a Yocto Project release tarball and unpacking it, or by cloning a copy of the upstream Poky Git repository. For information on both these methods, see the "Getting Set Up" section in the Yocto Project Development Manual.