1 files changed, 135 insertions, 0 deletions

diff --git a/documentation/dev-manual/custom-distribution.rst b/documentation/dev-manual/custom-distribution.rst
new file mode 100644
index 0000000000..0bc386d606
--- /dev/null
+++ b/documentation/dev-manual/custom-distribution.rst
@@ -0,0 +1,135 @@
+.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
+
+Creating Your Own Distribution
+******************************
+
+When you build an image using the Yocto Project and do not alter any
+distribution :term:`Metadata`, you are using the Poky distribution.
+Poky is explicitly a *reference* distribution for testing and
+development purposes. It enables most hardware and software features
+so that they can be tested, but this also means that from a security
+point of view the attack surface is very large. Additionally, at some
+point it is likely that you will want to gain more control over package
+alternative selections, compile-time options, and other low-level
+configurations. For both of these reasons, if you are using the Yocto
+Project for production use then you are strongly encouraged to create
+your own distribution.
+
+To create your own distribution, the basic steps consist of creating
+your own distribution layer, creating your own distribution
+configuration file, and then adding any needed code and Metadata to the
+layer. The following steps provide some more detail:
+
+-  *Create a layer for your new distro:* Create your distribution layer
+   so that you can keep your Metadata and code for the distribution
+   separate. It is strongly recommended that you create and use your own
+   layer for configuration and code. Using your own layer as compared to
+   just placing configurations in a ``local.conf`` configuration file
+   makes it easier to reproduce the same build configuration when using
+   multiple build machines. See the
+   ":ref:`dev-manual/layers:creating a general layer using the \`\`bitbake-layers\`\` script`"
+   section for information on how to quickly set up a layer.
+
+-  *Create the distribution configuration file:* The distribution
+   configuration file needs to be created in the ``conf/distro``
+   directory of your layer. You need to name it using your distribution
+   name (e.g. ``mydistro.conf``).
+
+   .. note::
+
+      The :term:`DISTRO` variable in your ``local.conf`` file determines the
+      name of your distribution.
+
+   You can split out parts of your configuration file into include files
+   and then "require" them from within your distribution configuration
+   file. Be sure to place the include files in the
+   ``conf/distro/include`` directory of your layer. A common example
+   usage of include files would be to separate out the selection of
+   desired version and revisions for individual recipes.
+
+   Your configuration file needs to set the following required
+   variables:
+
+   - :term:`DISTRO_NAME`
+
+   - :term:`DISTRO_VERSION`
+
+   These following variables are optional and you typically set them
+   from the distribution configuration file:
+
+   - :term:`DISTRO_FEATURES`
+
+   - :term:`DISTRO_EXTRA_RDEPENDS`
+
+   - :term:`DISTRO_EXTRA_RRECOMMENDS`
+
+   - :term:`TCLIBC`
+
+   .. tip::
+
+      If you want to base your distribution configuration file on the
+      very basic configuration from OE-Core, you can use
+      ``conf/distro/defaultsetup.conf`` as a reference and just include
+      variables that differ as compared to ``defaultsetup.conf``.
+      Alternatively, you can create a distribution configuration file
+      from scratch using the ``defaultsetup.conf`` file or configuration files
+      from another distribution such as Poky as a reference.
+
+-  *Provide miscellaneous variables:* Be sure to define any other
+   variables for which you want to create a default or enforce as part
+   of the distribution configuration. You can include nearly any
+   variable from the ``local.conf`` file. The variables you use are not
+   limited to the list in the previous bulleted item.
+
+-  *Point to Your distribution configuration file:* In your ``local.conf``
+   file in the :term:`Build Directory`, set your :term:`DISTRO` variable to
+   point to your distribution's configuration file. For example, if your
+   distribution's configuration file is named ``mydistro.conf``, then
+   you point to it as follows::
+
+      DISTRO = "mydistro"
+
+-  *Add more to the layer if necessary:* Use your layer to hold other
+   information needed for the distribution:
+
+   -  Add recipes for installing distro-specific configuration files
+      that are not already installed by another recipe. If you have
+      distro-specific configuration files that are included by an
+      existing recipe, you should add an append file (``.bbappend``) for
+      those. For general information and recommendations on how to add
+      recipes to your layer, see the
+      ":ref:`dev-manual/layers:creating your own layer`" and
+      ":ref:`dev-manual/layers:following best practices when creating layers`"
+      sections.
+
+   -  Add any image recipes that are specific to your distribution.
+
+   -  Add a ``psplash`` append file for a branded splash screen, using
+      the :term:`SPLASH_IMAGES` variable.
+
+   -  Add any other append files to make custom changes that are
+      specific to individual recipes.
+
+   For information on append files, see the
+   ":ref:`dev-manual/layers:appending other layers metadata with your layer`"
+   section.
+
+Copying and modifying the Poky distribution
+===========================================
+
+Instead of creating a custom distribution from scratch as per above, you may
+wish to start your custom distribution configuration by copying the Poky
+distribution provided within the ``meta-poky`` layer and then modifying it.
+This is fine, however if you do this you should keep the following in mind:
+
+-  Every reference to Poky needs to be updated in your copy so that it
+   will still apply. This includes override usage within files (e.g. ``:poky``)
+   and in directory names. This is a good opportunity to evaluate each one of
+   these customizations to see if they are needed for your use case.
+
+-  Unless you also intend to use them, the ``poky-tiny``, ``poky-altcfg`` and
+   ``poky-bleeding`` variants and any references to them can be removed.
+
+-  More generally, the Poky distribution configuration enables a lot more
+   than you likely need for your production use case. You should evaluate *every*
+   configuration choice made in your copy to determine if it is needed.