# Reference: Directory Structure

Poky consists of several components. Understanding them and knowing where they are located is key to using Poky well. This appendix describes the Poky directory structure and gives information about the various files and directories.

## Top level core components

### `bitbake/`

Poky includes a copy of BitBake for ease of use. The copy usually matches the current stable BitBake release from the BitBake project. BitBake, a metadata interpreter, reads the Poky metadata and runs the tasks defined by that data. Failures are usually from the metadata and not from BitBake itself. Consequently, most users do not need to worry about BitBake. The `bitbake/bin/` directory is placed into the PATH environment variable by the oe-init-build-env script.

For more information on BitBake, see the BitBake on-line manual at .

### `build/`

This directory contains user configuration files and the output generated by Poky in its standard configuration where the source tree is combined with the output. It is also possible to place output and configuration files in a directory separate from the Poky source. For information on separating output from the Poky source, see oe-init-build-env.

### `meta/`

This directory contains the core metadata, which is a key part of Poky. This directory contains the machine definitions, the Poky distribution, and the packages that make up a given system.

### `meta-demoapps/`

This directory contains recipes for applications and demos that are not core.

### `meta-rt/`

This directory contains recipes for RealTime.

### `scripts/`

This directory contains various integration scripts that implement extra functionality in the Poky environment (e.g. QEMU scripts). The oe-init-build-env script appends this directory to the PATH environment variable.

### `documentation`

This directory holds the source for the documentation. Each manual is contained in a sub-folder. For example, the files for this manual reside in `poky-ref-manual`.

### `oe-init-build-env`

This script sets up the Poky build environment. Sourcing this file in a shell makes changes to PATH and sets other core BitBake variables based on the current working directory. You need to run this script before running Poky commands. The script uses other scripts within the `scripts/` directory to do the bulk of the work. You can use this script to specify any directory for the build's output by doing the following:

         $ source POKY_SRC/oe-init-build-env [BUILDDIR]

You can enter the above command from any directory, as long as POKY_SRC points to the desired Poky source tree. The optional BUILDDIR can be any directory into which you would like Poky to generate the build output.

### `LICENSE, README, and README.hardware`

These files are standard top-level files.

## The Build Directory - `build/`

### `build/pseudodone`

This tag file indicates that the intitial pseudo binar was created. The first time BitBake is invoked this file is built.

### `build/conf/local.conf`

This file contains all the local user configuration of Poky. If there is no `local.conf` present, it is created from `local.conf.sample`. The `local.conf` file contains documentation on the various configuration options. Any variable set here overrides any variable set elsewhere within Poky unless that variable is hard-coded within Poky (e.g. by using '=' instead of '?='). Some variables are hard-coded for various reasons but these variables are relatively rare.

Edit this file to set the MACHINE for which you want to build, which package types you wish to use (PACKAGE_CLASSES) or where you want to downloaded files (DL_DIR).

### `build/conf/bblayers.conf`

This file defines layers, which is a directory tree, traversed (or walked) by BitBake. If `bblayers.conf` is not present, it is created from `bblayers.conf.sample` when the environment setup script is sourced.

### `build/conf/sanity_info`

This file is created during the build to indicate the state of the sanity checks.

### `build/downloads/`

This directory is used for the upstream source tarballs. The directory can be reused by multiple builds or moved to another location. You can control the location of this directory through the DL_DIR variable.

### `build/sstate-cache/`

This directory is used for the shared state cache. The directory can be reused by multiple builds or moved to another location. You can control the location of this directory through the SSTATE_DIR variable.

### `build/tmp/`

This directory receives all the Poky output. BitBake creates this directory if it does not exist. To clean Poky and start a build from scratch (other than downloads), you can remove everything in this directory or get rid of the directory completely. The `tmp/` directory has some important sub-components detailed below.

### `build/tmp/buildstats/`

This directory stores the build statistics.

### `build/tmp/cache/`

When BitBake parses the metadata it creates a cache file of the result that can be used when subsequently running commands. These results are stored here on a per-machine basis.

### `build/tmp/deploy/`

This directory contains any 'end result' output from Poky.

### `build/tmp/deploy/deb/`

This directory receives any `.deb` packages produced by Poky. The packages are sorted into feeds for different architecture types.

### `build/tmp/deploy/rpm/`

This directory receives any `.rpm` packages produced by Poky. The packages re sorted into feeds for different architecture types.

### `build/tmp/deploy/images/`

This directory receives complete filesystem images. If you want to flash the resulting image from a build onto a device, look here for the image.

### `build/tmp/deploy/ipk/`

This directory receives `.ipk` packages produced by Poky.

### `build/tmp/sysroots/`

This directory contains shared header files and libraries as well as other shared data. Packages that need to share output with other packages do so within this directory. The directory is subdivided by architecture so multiple builds can run within the one build directory.

### `build/tmp/stamps/`

This directory holds information that that BitBake uses for accounting purposes to track what tasks have run and when they have run. The directory is sub-divided by architecture. The files in the directory are empty of data. However, BitBake uses the filenames and timestamps for tracking purposes.

### `build/tmp/log/`

This directory contains general logs that are not otherwise placed using the package's WORKDIR. Examples of logs are the output from the "check_pkg" or "distro_check" tasks.

### `build/tmp/pkgdata/`

This directory contains intermediate packaging data that is used later in the packaging process. For more information, see package.bbclass.

### `build/tmp/pstagelogs/`

This directory contains manifest for task-based pre-built. Each manifest is basically a file list for installed files from a given task. Manifests are useful for later packaging or cleanup processes.

### `build/tmp/work/`

This directory contains architecture-specific work sub-directories for packages built by BitBake. All tasks execute from a work directory. For example, the source for a particular package is unpacked, patched, configured and compiled all within its own work directory.

It is worth considering the structure of a typical work directory. As an example consider the linux-rp kernel, version 2.6.20 r7 on the machine spitz built within Poky. For this package a work directory of `tmp/work/spitz-poky-linux-gnueabi/linux-rp-2.6.20-r7/`, referred to as WORKDIR, is created. Within this directory, the source is unpacked to linux-2.6.20 and then patched by quilt (see Section 3.5.1). Within the `linux-2.6.20` directory, standard quilt directories `linux-2.6.20/patches` and `linux-2.6.20/.pc` are created, and standard quilt commands can be used.

There are other directories generated within WORKDIR. The most important directory is WORKDIR `/temp/`, which has log files for each task (`log.do_*.pid`) and contains the scripts BitBake runs for each task (`run.do_*.pid`). The WORKDIR`/image/` directory is where "make install" places its output that is then split into sub-packages within WORKDIR`/packages-split/`.

## The Metadata - `meta/`

As mentioned previously, metadata is the core of Poky. Metadata has several important subdivisions:

### `meta/classes/`

This directory contains the `*.bbclass` files. Class files are used to abstract common code so it can be reused by multiple packages. Every package inherits the `base.bbclass` file. Examples of other important classes are `autotools.bbclass`, which in theory allows any Autotool-enabled package to work with Poky with minimal effort. Another example is `kernel.bbclass` that contains common code and functions for working with the Linux kernel. Functions like image generation or packaging also have their specific class files such as `image.bbclass`, `rootfs_*.bbclass` and `package*.bbclass`.

### `meta/conf/`

This directory contains the core set of configuration files that start from `bitbake.conf` and from which all other configuration files are included. See the includes at the end of the file and you will note that even `local.conf` is loaded from there! While `bitbake.conf` sets up the defaults, you can often override these by using the (`local.conf`) file, machine file or the distribution configuration file.

### `meta/conf/machine/`

This directory contains all the machine configuration files. If you set MACHINE="spitz", Poky looks for a `spitz.conf` file in this directory. The includes directory contains various data common to multiple machines. If you want to add support for a new machine to Poky, look in this directory.

### `meta/conf/distro/`

Any distribution-specific configuration is controlled from this directory. Poky only contains the Poky distribution so `poky.conf` is the main file here. This directory includes the versions and SRCDATES for applications that are configured here. An example of an alternative configuration is `poky-bleeding.conf` although this file mainly inherits its configuration from Poky itself.

### `meta/recipes-bsp/`

This directory contains anything linking to specific hardware or hardware configuration information such as "uboot" and "grub".

### `meta/recipes-connectivity/`

This directory contains libraries and applications related to communication with other devices.

### `meta/recipes-core/`

This directory contains what is needed to build a basic working Linux image including commonly used dependencies.

### `meta/recipes-devtools/`

This directory contains tools that are primarily used by the build system. The tools, however, can also be used on targets.

### `meta/recipes-extended/`

This directory contains non-essential applications that add features compared to the alternatives in core. You might need this directory for full tool functionality or for Linux Standard Base (LSB) compliance.

### `meta/recipes-gnome/`

This directory contains all things related to the GTK+ application framework.

### `meta/recipes-graphics/`

This directory contains X and other graphically related system libraries

### `meta/recipes-kernel/`

This directory contains the kernel and generic applications and libraries that have strong kernel dependencies.

### `meta/recipes-multimedia/`

This directory contains codecs and support utilities for audio, images and video.

### `meta/recipes-qt/`

This directory contains all things related to the QT application framework.

### `meta/recipes-sato/`

This directory contains the Sato demo/reference UI/UX and its associated applications and configuration data.

### `meta/recipes-support/`

This directory contains recipes that used by other recipes, but that are not directly included in images (i.e. depenendies of other recipes).

### `meta/site/`

This directory contains a list of cached results for various architectures. Because certain "autoconf" test results cannot be determined when cross-compiling due to the tests not able to run on a live system, the information in this directory is passed to "autoconf" for the various architectures.

### `meta/recipes.txt/`

This file is a description of the contents of `recipes-*`.