# Reference: Directory Structure

Poky consists of several components and understanding what these are and where they're located is one of the keys to using it. This section walks through the Poky directory structure giving information about the various files and directories.

## Top level core components

### `bitbake/`

A copy of BitBake is included within Poky for ease of use, and should usually match the current BitBake stable release from the BitBake project. Bitbake, a metadata interpreter, reads the Poky metadata and runs the tasks defined in the Poky metadata. Failures are usually from the metadata, not BitBake itself, so most users don't need to worry about BitBake. The `bitbake/bin/` directory is placed into the PATH environment variable by the poky-init-build-env script.

For more information on BitBake please see the BitBake project site at and the BitBake on-line manual at .

### `build/`

This directory contains user configuration files and the output from Poky.

### `meta/`

This directory contains the core metadata, a key part of Poky. Within this directory there are definitions of the machines, the Poky distribution and the packages that make up a given system.

### `meta-extras/`

This directory is similar to `meta/`, and contains some extra metadata not included in standard Poky. These are disabled by default, and are not supported as part of Poky.

### `scripts/`

This directory contains various integration scripts which implement extra functionality in the Poky environment, such as the QEMU scripts. This directory is appended to the PATH environment variable by the poky-init-build-env script.

### `sources/`

While not part of a checkout, Poky will create this directory as part of any build. Any downloads are placed in this directory (as specified by the DL_DIR variable). This directory can be shared between Poky builds to save downloading files multiple times. SCM checkouts are also stored here as e.g. `sources/svn/` , `sources/cvs/` or `sources/git/` and the sources directory may contain archives of checkouts for various revisions or dates.

It's worth noting that BitBake creates `.md5` stamp files for downloads. It uses these to mark downloads as complete as well as for checksum and access accounting purposes. If you add a file manually to the directory, you need to touch the corresponding `.md5` file too.

This location can be overridden by setting DL_DIR in `local.conf` . This directory can be shared between builds and even between machines via NFS, so downloads are only made once, speeding up builds.

### `poky-init-build-env`

This script is used to setup 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 use this before running Poky commands. Internally it uses scripts within the `scripts/` directory to do the bulk of the work.

## `build/` - The Build Directory

### `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 hardcoded within Poky (e.g. by using '=' instead of '?='). Some variables are hardcoded 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 downloaded files should go (DL_DIR).

### `build/tmp/`

This is created by BitBake if it doesn't exist and is where all the Poky output is placed. To clean Poky and start a build from scratch (other than downloads), you can wipe this directory. The `tmp/` directory has some important sub-components detailed below.

### `build/tmp/cache/`

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

### `build/tmp/deploy/`

Any 'end result' output from Poky is placed under here.

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

Any .deb packages emitted by Poky are placed here, sorted into feeds for different architecture types.

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

Complete filesystem images are placed here. If you want to flash the resulting image from a build onto a device, look here for them.

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

Any resulting .ipk packages emitted by Poky are placed here.

### `build/tmp/rootfs/`

This is a temporary scratch area used when creating filesystem images. It is run under fakeroot and is not useful once that fakeroot session has ended as information is lost. It is left around since it is still useful in debugging image creation problems.

### `build/tmp/sysroots/`

Any package needing to share output with other packages does so within sysroots. This means it contains any shared header files and any shared libraries amongst other data. It is subdivided by architecture so multiple builds can run within the one build directory.

### `build/tmp/stamps/`

This is used by BitBake for accounting purposes to keep track of which tasks have been run and when. It is also subdivided by architecture. The files are empty and the important information is the filenames and timestamps.

### `build/tmp/work/`

This directory contains various subdirectories for each architecture, and each package built by BitBake has its own work directory under the appropriate architecture subdirectory. All tasks are executed from this work directory. As an example, the source for a particular package will be unpacked, patched, configured and compiled all within its own work directory.

It is worth considering the structure of a typical work directory. An example is 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 is WORKDIR `/temp/` which has log files for each task (`log.do_*.pid`) and the scripts BitBake runs for each task (`run.do_*.pid`). The WORKDIR `/image/` directory is where `make install` places its output which is then split into subpackages within WORKDIR `/install/`.

## `meta/` - The Metadata

As mentioned previously, this is the core of Poky. It has several important subdivisions:

### `meta/classes/`

Contains the `*.bbclass` files. Class files are used to abstract common code allowing it to be reused by multiple packages. The `base.bbclass` file is inherited by every package. Examples of other important classes are `autotools.bbclass` that in theory allows any Autotool-enabled package to work with Poky with minimal effort, or `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 (`image.bbclass` , `rootfs_*.bbclass` and `package*.bbclass`).

### `meta/conf/`

This is the core set of configuration files which start from `bitbake.conf` and from which all other configuration files are included (see the includes at the end of the file, even `local.conf` is loaded from there!). While `bitbake.conf` sets up the defaults, these can often be overridden by user (`local.conf`), machine or distribution configuration files.

### `meta/conf/machine/`

Contains all the machine configuration files. If you set MACHINE="spitz", the end result is Poky looking 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, this is the directory to look in.

### `meta/conf/distro/`

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

### `meta/packages/`

Each application (package) Poky can build has an associated .bb file which are all stored under this directory. Poky finds them through the BBFILES variable which defaults to packages/*/*.bb. Adding a new piece of software to Poky consists of adding the appropriate .bb file. The .bb files from OpenEmbedded upstream are usually compatible although they are not supported.

### `meta/site/`

Certain autoconf test results cannot be determined when cross compiling since it can't run tests on a live system. This directory therefore contains a list of cached results for various architectures which is passed to autoconf.