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.. SPDX-License-Identifier: CC-BY-SA-2.0-UK
************************
Using the Extensible SDK
************************
This chapter describes the extensible SDK and how to install it.
Information covers the pieces of the SDK, how to install it, and
presents a look at using the ``devtool`` functionality. The extensible
SDK makes it easy to add new applications and libraries to an image,
modify the source for an existing component, test changes on the target
hardware, and ease integration into the rest of the
:term:`OpenEmbedded Build System`.
.. note::
For a side-by-side comparison of main features supported for an
extensible SDK as compared to a standard SDK, see the
:ref:`sdk-manual/intro:introduction` section.
In addition to the functionality available through ``devtool``, you can
alternatively make use of the toolchain directly, for example from
Makefile and Autotools. See the
":ref:`sdk-manual/working-projects:using the sdk toolchain directly`" chapter
for more information.
Why use the Extensible SDK and What is in It?
=============================================
The extensible SDK provides a cross-development toolchain and libraries
tailored to the contents of a specific image. You would use the
Extensible SDK if you want a toolchain experience supplemented with the
powerful set of ``devtool`` commands tailored for the Yocto Project
environment.
The installed extensible SDK consists of several files and directories.
Basically, it contains an SDK environment setup script, some
configuration files, an internal build system, and the ``devtool``
functionality.
Installing the Extensible SDK
=============================
Two ways to install the Extensible SDK
--------------------------------------
Extensible SDK can be installed in two different ways, and both have
their own pros and cons:
#. *Setting up the Extensible SDK environment directly in a Yocto build*. This
avoids having to produce, test, distribute and maintain separate SDK
installer archives, which can get very large. There is only one environment
for the regular Yocto build and the SDK and less code paths where things can
go not according to plan. It's easier to update the SDK: it simply means
updating the Yocto layers with git fetch or layer management tooling. The
SDK extensibility is better than in the second option: just run ``bitbake``
again to add more things to the sysroot, or add layers if even more things
are required.
#. *Setting up the Extensible SDK from a standalone installer*. This has the
benefit of having a single, self-contained archive that includes all the
needed binary artifacts. So nothing needs to be rebuilt, and there is no
need to provide a well-functioning binary artefact cache over the network
for developers with underpowered laptops.
Setting up the Extensible SDK environment directly in a Yocto build
-------------------------------------------------------------------
#. Set up all the needed layers and a Yocto :term:`Build Directory`, e.g. a regular Yocto
build where ``bitbake`` can be executed.
#. Run::
$ bitbake meta-ide-support
$ bitbake -c populate_sysroot gtk+3
# or any other target or native item that the application developer would need
$ bitbake build-sysroots
Setting up the Extensible SDK from a standalone installer
---------------------------------------------------------
The first thing you need to do is install the SDK on your :term:`Build
Host` by running the ``*.sh`` installation script.
You can download a tarball installer, which includes the pre-built
toolchain, the ``runqemu`` script, the internal build system,
``devtool``, and support files from the appropriate
:yocto_dl:`toolchain </releases/yocto/yocto-&DISTRO;/toolchain/>` directory within the Index of
Releases. Toolchains are available for several 32-bit and 64-bit
architectures with the ``x86_64`` directories, respectively. The
toolchains the Yocto Project provides are based off the
``core-image-sato`` and ``core-image-minimal`` images and contain
libraries appropriate for developing against that image.
The names of the tarball installer scripts are such that a string
representing the host system appears first in the filename and then is
immediately followed by a string representing the target architecture.
An extensible SDK has the string "-ext" as part of the name. Following
is the general form::
poky-glibc-host_system-image_type-arch-toolchain-ext-release_version.sh
Where:
host_system is a string representing your development system:
i686 or x86_64.
image_type is the image for which the SDK was built:
core-image-sato or core-image-minimal
arch is a string representing the tuned target architecture:
aarch64, armv5e, core2-64, i586, mips32r2, mips64, ppc7400, or cortexa8hf-neon
release_version is a string representing the release number of the Yocto Project:
&DISTRO;, &DISTRO;+snapshot
For example, the following SDK installer is for a 64-bit
development host system and a i586-tuned target architecture based off
the SDK for ``core-image-sato`` and using the current &DISTRO; snapshot::
poky-glibc-x86_64-core-image-sato-i586-toolchain-ext-&DISTRO;.sh
.. note::
As an alternative to downloading an SDK, you can build the SDK
installer. For information on building the installer, see the
:ref:`sdk-manual/appendix-obtain:building an sdk installer`
section.
The SDK and toolchains are self-contained and by default are installed
into the ``poky_sdk`` folder in your home directory. You can choose to
install the extensible SDK in any location when you run the installer.
However, because files need to be written under that directory during
the normal course of operation, the location you choose for installation
must be writable for whichever users need to use the SDK.
The following command shows how to run the installer given a toolchain
tarball for a 64-bit x86 development host system and a 64-bit x86 target
architecture. The example assumes the SDK installer is located in
``~/Downloads/`` and has execution rights::
$ ./Downloads/poky-glibc-x86_64-core-image-minimal-core2-64-toolchain-ext-2.5.sh
Poky (Yocto Project Reference Distro) Extensible SDK installer version 2.5
==========================================================================
Enter target directory for SDK (default: poky_sdk):
You are about to install the SDK to "/home/scottrif/poky_sdk". Proceed [Y/n]? Y
Extracting SDK..............done
Setting it up...
Extracting buildtools...
Preparing build system...
Parsing recipes: 100% |##################################################################| Time: 0:00:52
Initialising tasks: 100% |###############################################################| Time: 0:00:00
Checking sstate mirror object availability: 100% |#######################################| Time: 0:00:00
Loading cache: 100% |####################################################################| Time: 0:00:00
Initialising tasks: 100% |###############################################################| Time: 0:00:00
done
SDK has been successfully set up and is ready to be used.
Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
$ . /home/scottrif/poky_sdk/environment-setup-core2-64-poky-linux
.. note::
If you do not have write permissions for the directory into which you
are installing the SDK, the installer notifies you and exits. For
that case, set up the proper permissions in the directory and run the
installer again.
Running the Extensible SDK Environment Setup Script
===================================================
Once you have the SDK installed, you must run the SDK environment setup
script before you can actually use the SDK.
When using a SDK directly in a Yocto build, you will find the script in
``tmp/deploy/images/qemux86-64/`` in your :term:`Build Directory`.
When using a standalone SDK installer, this setup script resides in
the directory you chose when you installed the SDK, which is either the
default ``poky_sdk`` directory or the directory you chose during
installation.
Before running the script, be sure it is the one that matches the
architecture for which you are developing. Environment setup scripts
begin with the string "``environment-setup``" and include as part of
their name the tuned target architecture. As an example, the following
commands set the working directory to where the SDK was installed and
then source the environment setup script. In this example, the setup
script is for an IA-based target machine using i586 tuning::
$ cd /home/scottrif/poky_sdk
$ source environment-setup-core2-64-poky-linux
SDK environment now set up; additionally you may now run devtool to perform development tasks.
Run devtool --help for further details.
When using the environment script directly in a Yocto build, it can
be run similarly::
$ source tmp/deploy/images/qemux86-64/environment-setup-core2-64-poky-linux
Running the setup script defines many environment variables needed in order to
use the SDK (e.g. ``PATH``, :term:`CC`, :term:`LD`, and so forth). If you want
to see all the environment variables the script exports, examine the
installation file itself.
Using ``devtool`` in Your SDK Workflow
======================================
The cornerstone of the extensible SDK is a command-line tool called
``devtool``. This tool provides a number of features that help you
build, test and package software within the extensible SDK, and
optionally integrate it into an image built by the OpenEmbedded build
system.
.. note::
The use of ``devtool`` is not limited to the extensible SDK. You can use
``devtool`` to help you easily develop any project whose build output must be
part of an image built using the build system.
The ``devtool`` command line is organized similarly to
:ref:`overview-manual/development-environment:git` in that it has a number of
sub-commands for each function. You can run ``devtool --help`` to see
all the commands.
.. note::
See the ":doc:`/ref-manual/devtool-reference`"
section in the Yocto Project Reference Manual.
Three ``devtool`` subcommands provide entry-points into development:
- *devtool add*: Assists in adding new software to be built.
- *devtool modify*: Sets up an environment to enable you to modify
the source of an existing component.
- *devtool upgrade*: Updates an existing recipe so that you can
build it for an updated set of source files.
As with the build system, "recipes" represent software packages within
``devtool``. When you use ``devtool add``, a recipe is automatically
created. When you use ``devtool modify``, the specified existing recipe
is used in order to determine where to get the source code and how to
patch it. In both cases, an environment is set up so that when you build
the recipe a source tree that is under your control is used in order to
allow you to make changes to the source as desired. By default, new
recipes and the source go into a "workspace" directory under the SDK.
The remainder of this section presents the ``devtool add``,
``devtool modify``, and ``devtool upgrade`` workflows.
Use ``devtool add`` to Add an Application
-----------------------------------------
The ``devtool add`` command generates a new recipe based on existing
source code. This command takes advantage of the
:ref:`devtool-the-workspace-layer-structure`
layer that many ``devtool`` commands use. The command is flexible enough
to allow you to extract source code into both the workspace or a
separate local Git repository and to use existing code that does not
need to be extracted.
Depending on your particular scenario, the arguments and options you use
with ``devtool add`` form different combinations. The following diagram
shows common development flows you would use with the ``devtool add``
command:
.. image:: figures/sdk-devtool-add-flow.png
:width: 100%
#. *Generating the New Recipe*: The top part of the flow shows three
scenarios by which you could use ``devtool add`` to generate a recipe
based on existing source code.
In a shared development environment, it is typical for other
developers to be responsible for various areas of source code. As a
developer, you are probably interested in using that source code as
part of your development within the Yocto Project. All you need is
access to the code, a recipe, and a controlled area in which to do
your work.
Within the diagram, three possible scenarios feed into the
``devtool add`` workflow:
- *Left*: The left scenario in the figure represents a common
situation where the source code does not exist locally and needs
to be extracted. In this situation, the source code is extracted
to the default workspace --- you do not want the files in some
specific location outside of the workspace. Thus, everything you
need will be located in the workspace::
$ devtool add recipe fetchuri
With this command, ``devtool`` extracts the upstream
source files into a local Git repository within the ``sources``
folder. The command then creates a recipe named recipe and a
corresponding append file in the workspace. If you do not provide
recipe, the command makes an attempt to determine the recipe name.
- *Middle*: The middle scenario in the figure also represents a
situation where the source code does not exist locally. In this
case, the code is again upstream and needs to be extracted to some
local area --- this time outside of the default workspace.
.. note::
If required, ``devtool`` always creates a Git repository locally
during the extraction.
Furthermore, the first positional argument ``srctree`` in this case
identifies where the ``devtool add`` command will locate the
extracted code outside of the workspace. You need to specify an
empty directory::
$ devtool add recipe srctree fetchuri
In summary, the source code is pulled from fetchuri and extracted into the
location defined by ``srctree`` as a local Git repository.
Within workspace, ``devtool`` creates a recipe named recipe along
with an associated append file.
- *Right*: The right scenario in the figure represents a situation
where the ``srctree`` has been previously prepared outside of the
``devtool`` workspace.
The following command provides a new recipe name and identifies
the existing source tree location::
$ devtool add recipe srctree
The command examines the source code and creates a recipe named
recipe for the code and places the recipe into the workspace.
Because the extracted source code already exists, ``devtool`` does
not try to relocate the source code into the workspace --- only the
new recipe is placed in the workspace.
Aside from a recipe folder, the command also creates an associated
append folder and places an initial ``*.bbappend`` file within.
#. *Edit the Recipe*: You can use ``devtool edit-recipe`` to open up the
editor as defined by the ``$EDITOR`` environment variable and modify
the file::
$ devtool edit-recipe recipe
From within the editor, you can make modifications to the recipe that
take effect when you build it later.
#. *Build the Recipe or Rebuild the Image*: The next step you take
depends on what you are going to do with the new code.
If you need to eventually move the build output to the target
hardware, use the following ``devtool`` command::
$ devtool build recipe
On the other hand, if you want an image to contain the recipe's
packages from the workspace for immediate deployment onto a device
(e.g. for testing purposes), you can use the ``devtool build-image``
command::
$ devtool build-image image
#. *Deploy the Build Output*: When you use the ``devtool build`` command
to build out your recipe, you probably want to see if the resulting
build output works as expected on the target hardware.
.. note::
This step assumes you have a previously built image that is
already either running in QEMU or is running on actual hardware.
Also, it is assumed that for deployment of the image to the
target, SSH is installed in the image and, if the image is running
on real hardware, you have network access to and from your
development machine.
You can deploy your build output to that target hardware by using the
``devtool deploy-target`` command::
$ devtool deploy-target recipe target
The target is a live target machine running as an SSH server.
You can, of course, also deploy the image you build to actual
hardware by using the ``devtool build-image`` command. However,
``devtool`` does not provide a specific command that allows you to
deploy the image to actual hardware.
#. *Finish Your Work With the Recipe*: The ``devtool finish`` command
creates any patches corresponding to commits in the local Git
repository, moves the new recipe to a more permanent layer, and then
resets the recipe so that the recipe is built normally rather than
from the workspace::
$ devtool finish recipe layer
.. note::
Any changes you want to turn into patches must be committed to the
Git repository in the source tree.
As mentioned, the ``devtool finish`` command moves the final recipe
to its permanent layer.
As a final process of the ``devtool finish`` command, the state of
the standard layers and the upstream source is restored so that you
can build the recipe from those areas rather than the workspace.
.. note::
You can use the ``devtool reset`` command to put things back should you
decide you do not want to proceed with your work. If you do use this
command, realize that the source tree is preserved.
Use ``devtool modify`` to Modify the Source of an Existing Component
--------------------------------------------------------------------
The ``devtool modify`` command prepares the way to work on existing code
that already has a local recipe in place that is used to build the
software. The command is flexible enough to allow you to extract code
from an upstream source, specify the existing recipe, and keep track of
and gather any patch files from other developers that are associated
with the code.
Depending on your particular scenario, the arguments and options you use
with ``devtool modify`` form different combinations. The following
diagram shows common development flows for the ``devtool modify``
command:
.. image:: figures/sdk-devtool-modify-flow.png
:width: 100%
#. *Preparing to Modify the Code*: The top part of the flow shows three
scenarios by which you could use ``devtool modify`` to prepare to
work on source files. Each scenario assumes the following:
- The recipe exists locally in a layer external to the ``devtool``
workspace.
- The source files exist either upstream in an un-extracted state or
locally in a previously extracted state.
The typical situation is where another developer has created a layer
for use with the Yocto Project and their recipe already resides in
that layer. Furthermore, their source code is readily available
either upstream or locally.
- *Left*: The left scenario in the figure represents a common
situation where the source code does not exist locally and it
needs to be extracted from an upstream source. In this situation,
the source is extracted into the default ``devtool`` workspace
location. The recipe, in this scenario, is in its own layer
outside the workspace (i.e. ``meta-``\ layername).
The following command identifies the recipe and, by default,
extracts the source files::
$ devtool modify recipe
Once ``devtool`` locates the recipe, ``devtool`` uses the recipe's
:term:`SRC_URI` statements to locate the source code and any local
patch files from other developers.
With this scenario, there is no ``srctree`` argument. Consequently, the
default behavior of the ``devtool modify`` command is to extract
the source files pointed to by the :term:`SRC_URI` statements into a
local Git structure. Furthermore, the location for the extracted
source is the default area within the ``devtool`` workspace. The
result is that the command sets up both the source code and an
append file within the workspace while the recipe remains in its
original location.
Additionally, if you have any non-patch local files (i.e. files
referred to with ``file://`` entries in :term:`SRC_URI` statement
excluding ``*.patch/`` or ``*.diff``), these files are copied to
an ``oe-local-files`` folder under the newly created source tree.
Copying the files here gives you a convenient area from which you
can modify the files. Any changes or additions you make to those
files are incorporated into the build the next time you build the
software just as are other changes you might have made to the
source.
- *Middle*: The middle scenario in the figure represents a situation
where the source code also does not exist locally. In this case,
the code is again upstream and needs to be extracted to some local
area as a Git repository. The recipe, in this scenario, is again
local and in its own layer outside the workspace.
The following command tells ``devtool`` the recipe with which to
work and, in this case, identifies a local area for the extracted
source files that exists outside of the default ``devtool``
workspace::
$ devtool modify recipe srctree
.. note::
You cannot provide a URL for ``srctree`` using the ``devtool`` command.
As with all extractions, the command uses the recipe's :term:`SRC_URI`
statements to locate the source files and any associated patch
files. Non-patch files are copied to an ``oe-local-files`` folder
under the newly created source tree.
Once the files are located, the command by default extracts them
into ``srctree``.
Within workspace, ``devtool`` creates an append file for the
recipe. The recipe remains in its original location but the source
files are extracted to the location you provide with ``srctree``.
- *Right*: The right scenario in the figure represents a situation
where the source tree (``srctree``) already exists locally as a
previously extracted Git structure outside of the ``devtool``
workspace. In this example, the recipe also exists elsewhere
locally in its own layer.
The following command tells ``devtool`` the recipe with which to
work, uses the "-n" option to indicate source does not need to be
extracted, and uses ``srctree`` to point to the previously extracted
source files::
$ devtool modify -n recipe srctree
If an ``oe-local-files`` subdirectory happens to exist and it
contains non-patch files, the files are used. However, if the
subdirectory does not exist and you run the ``devtool finish``
command, any non-patch files that might exist next to the recipe
are removed because it appears to ``devtool`` that you have
deleted those files.
Once the ``devtool modify`` command finishes, it creates only an
append file for the recipe in the ``devtool`` workspace. The
recipe and the source code remain in their original locations.
#. *Edit the Source*: Once you have used the ``devtool modify`` command,
you are free to make changes to the source files. You can use any
editor you like to make and save your source code modifications.
#. *Build the Recipe or Rebuild the Image*: The next step you take
depends on what you are going to do with the new code.
If you need to eventually move the build output to the target
hardware, use the following ``devtool`` command::
$ devtool build recipe
On the other hand, if you want an image to contain the recipe's
packages from the workspace for immediate deployment onto a device
(e.g. for testing purposes), you can use the ``devtool build-image``
command::
$ devtool build-image image
#. *Deploy the Build Output*: When you use the ``devtool build`` command
to build out your recipe, you probably want to see if the resulting
build output works as expected on target hardware.
.. note::
This step assumes you have a previously built image that is
already either running in QEMU or running on actual hardware.
Also, it is assumed that for deployment of the image to the
target, SSH is installed in the image and if the image is running
on real hardware that you have network access to and from your
development machine.
You can deploy your build output to that target hardware by using the
``devtool deploy-target`` command::
$ devtool deploy-target recipe target
The target is a live target machine running as an SSH server.
You can, of course, use other methods to deploy the image you built
using the ``devtool build-image`` command to actual hardware.
``devtool`` does not provide a specific command to deploy the image
to actual hardware.
#. *Finish Your Work With the Recipe*: The ``devtool finish`` command
creates any patches corresponding to commits in the local Git
repository, updates the recipe to point to them (or creates a
``.bbappend`` file to do so, depending on the specified destination
layer), and then resets the recipe so that the recipe is built
normally rather than from the workspace::
$ devtool finish recipe layer
.. note::
Any changes you want to turn into patches must be staged and
committed within the local Git repository before you use the
``devtool finish`` command.
Because there is no need to move the recipe, ``devtool finish``
either updates the original recipe in the original layer or the
command creates a ``.bbappend`` file in a different layer as provided
by layer. Any work you did in the ``oe-local-files`` directory is
preserved in the original files next to the recipe during the
``devtool finish`` command.
As a final process of the ``devtool finish`` command, the state of
the standard layers and the upstream source is restored so that you
can build the recipe from those areas rather than from the workspace.
.. note::
You can use the ``devtool reset`` command to put things back should you
decide you do not want to proceed with your work. If you do use this
command, realize that the source tree is preserved.
Use ``devtool upgrade`` to Create a Version of the Recipe that Supports a Newer Version of the Software
-------------------------------------------------------------------------------------------------------
The ``devtool upgrade`` command upgrades an existing recipe to that of a
more up-to-date version found upstream. Throughout the life of software,
recipes continually undergo version upgrades by their upstream
publishers. You can use the ``devtool upgrade`` workflow to make sure
your recipes you are using for builds are up-to-date with their upstream
counterparts.
.. note::
Several methods exist by which you can upgrade recipes ---
``devtool upgrade`` happens to be one. You can read about all the methods by
which you can upgrade recipes in the
:ref:`dev-manual/upgrading-recipes:upgrading recipes` section of the Yocto
Project Development Tasks Manual.
The ``devtool upgrade`` command is flexible enough to allow you to specify
source code revision and versioning schemes, extract code into or out of the
``devtool`` :ref:`devtool-the-workspace-layer-structure`, and work with any
source file forms that the
:ref:`bitbake-user-manual/bitbake-user-manual-fetching:fetchers` support.
The following diagram shows the common development flow used with the
``devtool upgrade`` command:
.. image:: figures/sdk-devtool-upgrade-flow.png
:width: 100%
#. *Initiate the Upgrade*: The top part of the flow shows the typical
scenario by which you use the ``devtool upgrade`` command. The
following conditions exist:
- The recipe exists in a local layer external to the ``devtool``
workspace.
- The source files for the new release exist in the same location
pointed to by :term:`SRC_URI`
in the recipe (e.g. a tarball with the new version number in the
name, or as a different revision in the upstream Git repository).
A common situation is where third-party software has undergone a
revision so that it has been upgraded. The recipe you have access to
is likely in your own layer. Thus, you need to upgrade the recipe to
use the newer version of the software::
$ devtool upgrade -V version recipe
By default, the ``devtool upgrade`` command extracts source
code into the ``sources`` directory in the
:ref:`devtool-the-workspace-layer-structure`.
If you want the code extracted to any other location, you need to
provide the ``srctree`` positional argument with the command as follows::
$ devtool upgrade -V version recipe srctree
.. note::
In this example, the "-V" option specifies the new version. If you
don't use "-V", the command upgrades the recipe to the latest
version.
If the source files pointed to by the :term:`SRC_URI` statement in the
recipe are in a Git repository, you must provide the "-S" option and
specify a revision for the software.
Once ``devtool`` locates the recipe, it uses the :term:`SRC_URI` variable
to locate the source code and any local patch files from other
developers. The result is that the command sets up the source code,
the new version of the recipe, and an append file all within the
workspace.
Additionally, if you have any non-patch local files (i.e. files
referred to with ``file://`` entries in :term:`SRC_URI` statement
excluding ``*.patch/`` or ``*.diff``), these files are copied to an
``oe-local-files`` folder under the newly created source tree.
Copying the files here gives you a convenient area from which you can
modify the files. Any changes or additions you make to those files
are incorporated into the build the next time you build the software
just as are other changes you might have made to the source.
#. *Resolve any Conflicts created by the Upgrade*: Conflicts could happen
after upgrading the software to a new version. Conflicts occur
if your recipe specifies some patch files in :term:`SRC_URI` that
conflict with changes made in the new version of the software. For
such cases, you need to resolve the conflicts by editing the source
and following the normal ``git rebase`` conflict resolution process.
Before moving onto the next step, be sure to resolve any such
conflicts created through use of a newer or different version of the
software.
#. *Build the Recipe or Rebuild the Image*: The next step you take
depends on what you are going to do with the new code.
If you need to eventually move the build output to the target
hardware, use the following ``devtool`` command::
$ devtool build recipe
On the other hand, if you want an image to contain the recipe's
packages from the workspace for immediate deployment onto a device
(e.g. for testing purposes), you can use the ``devtool build-image``
command::
$ devtool build-image image
#. *Deploy the Build Output*: When you use the ``devtool build`` command
or ``bitbake`` to build your recipe, you probably want to see if the
resulting build output works as expected on target hardware.
.. note::
This step assumes you have a previously built image that is
already either running in QEMU or running on actual hardware.
Also, it is assumed that for deployment of the image to the
target, SSH is installed in the image and if the image is running
on real hardware that you have network access to and from your
development machine.
You can deploy your build output to that target hardware by using the
``devtool deploy-target`` command::
$ devtool deploy-target recipe target
The target is a live target machine running as an SSH server.
You can, of course, also deploy the image you build using the
``devtool build-image`` command to actual hardware. However,
``devtool`` does not provide a specific command that allows you to do
this.
#. *Finish Your Work With the Recipe*: The ``devtool finish`` command
creates any patches corresponding to commits in the local Git
repository, moves the new recipe to a more permanent layer, and then
resets the recipe so that the recipe is built normally rather than
from the workspace.
Any work you did in the ``oe-local-files`` directory is preserved in
the original files next to the recipe during the ``devtool finish``
command.
If you specify a destination layer that is the same as the original
source, then the old version of the recipe and associated files are
removed prior to adding the new version::
$ devtool finish recipe layer
.. note::
Any changes you want to turn into patches must be committed to the
Git repository in the source tree.
As a final process of the ``devtool finish`` command, the state of
the standard layers and the upstream source is restored so that you
can build the recipe from those areas rather than the workspace.
.. note::
You can use the ``devtool reset`` command to put things back should you
decide you do not want to proceed with your work. If you do use this
command, realize that the source tree is preserved.
A Closer Look at ``devtool add``
================================
The ``devtool add`` command automatically creates a recipe based on the
source tree you provide with the command. Currently, the command has
support for the following:
- Autotools (``autoconf`` and ``automake``)
- CMake
- Scons
- ``qmake``
- Plain ``Makefile``
- Out-of-tree kernel module
- Binary package (i.e. "-b" option)
- Node.js module
- Python modules that use ``setuptools`` or ``distutils``
Apart from binary packages, the determination of how a source tree
should be treated is automatic based on the files present within that
source tree. For example, if a ``CMakeLists.txt`` file is found, then
the source tree is assumed to be using CMake and is treated accordingly.
.. note::
In most cases, you need to edit the automatically generated recipe in
order to make it build properly. Typically, you would go through
several edit and build cycles until the recipe successfully builds.
Once the recipe builds, you could use possible further iterations to
test the recipe on the target device.
The remainder of this section covers specifics regarding how parts of
the recipe are generated.
Name and Version
----------------
If you do not specify a name and version on the command line,
``devtool add`` uses various metadata within the source tree in an
attempt to determine the name and version of the software being built.
Based on what the tool determines, ``devtool`` sets the name of the
created recipe file accordingly.
If ``devtool`` cannot determine the name and version, the command prints
an error. For such cases, you must re-run the command and provide the
name and version, just the name, or just the version as part of the
command line.
Sometimes the name or version determined from the source tree might be
incorrect. For such a case, you must reset the recipe::
$ devtool reset -n recipename
After running the ``devtool reset`` command, you need to
run ``devtool add`` again and provide the name or the version.
Dependency Detection and Mapping
--------------------------------
The ``devtool add`` command attempts to detect build-time dependencies and map
them to other recipes in the system. During this mapping, the command fills in
the names of those recipes as part of the :term:`DEPENDS` variable within the
recipe. If a dependency cannot be mapped, ``devtool`` places a comment
in the recipe indicating such. The inability to map a dependency can
result from naming not being recognized or because the dependency simply
is not available. For cases where the dependency is not available, you
must use the ``devtool add`` command to add an additional recipe that
satisfies the dependency. Once you add that recipe, you need to update
the :term:`DEPENDS` variable in the original recipe to include the new
recipe.
If you need to add runtime dependencies, you can do so by adding the
following to your recipe::
RDEPENDS:${PN} += "dependency1 dependency2 ..."
.. note::
The ``devtool add`` command often cannot distinguish between mandatory and
optional dependencies. Consequently, some of the detected dependencies might
in fact be optional. When in doubt, consult the documentation or the
configure script for the software the recipe is building for further
details. In some cases, you might find you can substitute the
dependency with an option that disables the associated functionality
passed to the configure script.
License Detection
-----------------
The ``devtool add`` command attempts to determine if the software you are
adding is able to be distributed under a common, open-source license. If
so, the command sets the :term:`LICENSE` value accordingly.
You should double-check the value added by the command against the
documentation or source files for the software you are building and, if
necessary, update that :term:`LICENSE` value.
The ``devtool add`` command also sets the :term:`LIC_FILES_CHKSUM`
value to point to all files that appear to be license-related. Realize
that license statements often appear in comments at the top of source
files or within the documentation. In such cases, the command does not
recognize those license statements. Consequently, you might need to
amend the :term:`LIC_FILES_CHKSUM` variable to point to one or more of those
comments if present. Setting :term:`LIC_FILES_CHKSUM` is particularly
important for third-party software. The mechanism attempts to ensure
correct licensing should you upgrade the recipe to a newer upstream
version in future. Any change in licensing is detected and you receive
an error prompting you to check the license text again.
If the ``devtool add`` command cannot determine licensing information,
``devtool`` sets the :term:`LICENSE` value to "CLOSED" and leaves the
:term:`LIC_FILES_CHKSUM` value unset. This behavior allows you to continue
with development even though the settings are unlikely to be correct in
all cases. You should check the documentation or source files for the
software you are building to determine the actual license.
Adding Makefile-Only Software
-----------------------------
The use of Make by itself is very common in both proprietary and
open-source software. Unfortunately, Makefiles are often not written
with cross-compilation in mind. Thus, ``devtool add`` often cannot do
very much to ensure that these Makefiles build correctly. It is very
common, for example, to explicitly call ``gcc`` instead of using the
:term:`CC` variable. Usually, in a
cross-compilation environment, ``gcc`` is the compiler for the build
host and the cross-compiler is named something similar to
``arm-poky-linux-gnueabi-gcc`` and might require arguments (e.g. to
point to the associated sysroot for the target machine).
When writing a recipe for Makefile-only software, keep the following in
mind:
- You probably need to patch the Makefile to use variables instead of
hardcoding tools within the toolchain such as ``gcc`` and ``g++``.
- The environment in which Make runs is set up with various standard
variables for compilation (e.g. :term:`CC`, :term:`CXX`, and so forth) in a
similar manner to the environment set up by the SDK's environment
setup script. One easy way to see these variables is to run the
``devtool build`` command on the recipe and then look in
``oe-logs/run.do_compile``. Towards the top of this file, there is
a list of environment variables that are set. You can take
advantage of these variables within the Makefile.
- If the Makefile sets a default for a variable using "=", that default
overrides the value set in the environment, which is usually not
desirable. For this case, you can either patch the Makefile so it
sets the default using the "?=" operator, or you can alternatively
force the value on the ``make`` command line. To force the value on
the command line, add the variable setting to
:term:`EXTRA_OEMAKE` or
:term:`PACKAGECONFIG_CONFARGS`
within the recipe. Here is an example using :term:`EXTRA_OEMAKE`::
EXTRA_OEMAKE += "'CC=${CC}' 'CXX=${CXX}'"
In the above example,
single quotes are used around the variable settings as the values are
likely to contain spaces because required default options are passed
to the compiler.
- Hardcoding paths inside Makefiles is often problematic in a
cross-compilation environment. This is particularly true because
those hardcoded paths often point to locations on the build host and
thus will either be read-only or will introduce contamination into
the cross-compilation because they are specific to the build host
rather than the target. Patching the Makefile to use prefix variables
or other path variables is usually the way to handle this situation.
- Sometimes a Makefile runs target-specific commands such as
``ldconfig``. For such cases, you might be able to apply patches that
remove these commands from the Makefile.
Adding Native Tools
-------------------
Often, you need to build additional tools that run on the :term:`Build Host`
as opposed to the target. You should indicate this requirement by using one of
the following methods when you run ``devtool add``:
- Specify the name of the recipe such that it ends with "-native".
Specifying the name like this produces a recipe that only builds for
the build host.
- Specify the "--also-native" option with the ``devtool add``
command. Specifying this option creates a recipe file that still
builds for the target but also creates a variant with a "-native"
suffix that builds for the build host.
.. note::
If you need to add a tool that is shipped as part of a source tree
that builds code for the target, you can typically accomplish this by
building the native and target parts separately rather than within
the same compilation process. Realize though that with the
"--also-native" option, you can add the tool using just one
recipe file.
Adding Node.js Modules
----------------------
You can use the ``devtool add`` command two different ways to add
Node.js modules: through ``npm`` or from a repository or local source.
Use the following form to add Node.js modules through ``npm``::
$ devtool add "npm://registry.npmjs.org;name=forever;version=0.15.1"
The name and
version parameters are mandatory. Lockdown and shrinkwrap files are
generated and pointed to by the recipe in order to freeze the version
that is fetched for the dependencies according to the first time. This
also saves checksums that are verified on future fetches. Together,
these behaviors ensure the reproducibility and integrity of the build.
.. note::
- You must use quotes around the URL. ``devtool add`` does not
require the quotes, but the shell considers ";" as a splitter
between multiple commands. Thus, without the quotes,
``devtool add`` does not receive the other parts, which results in
several "command not found" errors.
- In order to support adding Node.js modules, a ``nodejs`` recipe
must be part of your SDK.
As mentioned earlier, you can also add Node.js modules directly from a
repository or local source tree. To add modules this way, use
``devtool add`` in the following form::
$ devtool add https://github.com/diversario/node-ssdp
In this example, ``devtool`` fetches the specified Git repository, detects the
code as Node.js code, fetches dependencies using ``npm``, and sets
:term:`SRC_URI` accordingly.
Working With Recipes
====================
When building a recipe using the ``devtool build`` command, the typical
build progresses as follows:
#. Fetch the source
#. Unpack the source
#. Configure the source
#. Compile the source
#. Install the build output
#. Package the installed output
For recipes in the workspace, fetching and unpacking is disabled as the
source tree has already been prepared and is persistent. Each of these
build steps is defined as a function (task), usually with a "do\_" prefix
(e.g. :ref:`ref-tasks-fetch`,
:ref:`ref-tasks-unpack`, and so
forth). These functions are typically shell scripts but can instead be
written in Python.
If you look at the contents of a recipe, you will see that the recipe
does not include complete instructions for building the software.
Instead, common functionality is encapsulated in classes inherited with
the ``inherit`` directive. This technique leaves the recipe to describe
just the things that are specific to the software being built. There is
a :ref:`ref-classes-base` class that is implicitly inherited by all recipes
and provides the functionality that most recipes typically need.
The remainder of this section presents information useful when working
with recipes.
Finding Logs and Work Files
---------------------------
After the first run of the ``devtool build`` command, recipes that were
previously created using the ``devtool add`` command or whose sources
were modified using the ``devtool modify`` command contain symbolic
links created within the source tree:
- ``oe-logs``: This link points to the directory in which log files and
run scripts for each build step are created.
- ``oe-workdir``: This link points to the temporary work area for the
recipe. The following locations under ``oe-workdir`` are particularly
useful:
- ``image/``: Contains all of the files installed during the
:ref:`ref-tasks-install` stage.
Within a recipe, this directory is referred to by the expression
``${``\ :term:`D`\ ``}``.
- ``sysroot-destdir/``: Contains a subset of files installed within
:ref:`ref-tasks-install` that have been put into the shared sysroot. For
more information, see the
":ref:`dev-manual/new-recipe:sharing files between recipes`" section.
- ``packages-split/``: Contains subdirectories for each package
produced by the recipe. For more information, see the
":ref:`sdk-manual/extensible:packaging`" section.
You can use these links to get more information on what is happening at
each build step.
Setting Configure Arguments
---------------------------
If the software your recipe is building uses GNU autoconf, then a fixed
set of arguments is passed to it to enable cross-compilation plus any
extras specified by :term:`EXTRA_OECONF` or :term:`PACKAGECONFIG_CONFARGS`
set within the recipe. If you wish to pass additional options, add them
to :term:`EXTRA_OECONF` or :term:`PACKAGECONFIG_CONFARGS`. Other supported build
tools have similar variables (e.g. :term:`EXTRA_OECMAKE` for CMake,
:term:`EXTRA_OESCONS` for Scons, and so forth). If you need to pass anything on
the ``make`` command line, you can use :term:`EXTRA_OEMAKE` or the
:term:`PACKAGECONFIG_CONFARGS` variables to do so.
You can use the ``devtool configure-help`` command to help you set the
arguments listed in the previous paragraph. The command determines the
exact options being passed, and shows them to you along with any custom
arguments specified through :term:`EXTRA_OECONF` or
:term:`PACKAGECONFIG_CONFARGS`. If applicable, the command also shows you
the output of the configure script's "--help" option as a
reference.
Sharing Files Between Recipes
-----------------------------
Recipes often need to use files provided by other recipes on the
:term:`Build Host`. For example,
an application linking to a common library needs access to the library
itself and its associated headers. The way this access is accomplished
within the extensible SDK is through the sysroot. There is one sysroot per
"machine" for which the SDK is being built. In practical terms, this
means there is a sysroot for the target machine, and a sysroot for
the build host.
Recipes should never write files directly into the sysroot. Instead,
files should be installed into standard locations during the
:ref:`ref-tasks-install` task within the ``${``\ :term:`D`\ ``}`` directory. A
subset of these files automatically goes into the sysroot. The reason
for this limitation is that almost all files that go into the sysroot
are cataloged in manifests in order to ensure they can be removed later
when a recipe is modified or removed. Thus, the sysroot is able to
remain free from stale files.
Packaging
---------
Packaging is not always particularly relevant within the extensible SDK.
However, if you examine how build output gets into the final image on
the target device, it is important to understand packaging because the
contents of the image are expressed in terms of packages and not
recipes.
During the :ref:`ref-tasks-package` task, files installed during the
:ref:`ref-tasks-install` task are split into one main package, which is almost
always named the same as the recipe, and into several other packages. This
separation exists because not all of those installed files are useful in every
image. For example, you probably do not need any of the documentation installed
in a production image. Consequently, for each recipe the documentation
files are separated into a ``-doc`` package. Recipes that package
software containing optional modules or plugins might undergo additional
package splitting as well.
After building a recipe, you can see where files have gone by looking in
the ``oe-workdir/packages-split`` directory, which contains a
subdirectory for each package. Apart from some advanced cases, the
:term:`PACKAGES` and :term:`FILES` variables controls
splitting. The :term:`PACKAGES` variable lists all of the packages to be
produced, while the :term:`FILES` variable specifies which files to include
in each package by using an override to specify the package. For
example, ``FILES:${PN}`` specifies the files to go into the main package
(i.e. the main package has the same name as the recipe and
``${``\ :term:`PN`\ ``}`` evaluates to the
recipe name). The order of the :term:`PACKAGES` value is significant. For
each installed file, the first package whose :term:`FILES` value matches the
file is the package into which the file goes. Both the :term:`PACKAGES` and
:term:`FILES` variables have default values. Consequently, you might find
you do not even need to set these variables in your recipe unless the
software the recipe is building installs files into non-standard
locations.
Restoring the Target Device to its Original State
=================================================
If you use the ``devtool deploy-target`` command to write a recipe's
build output to the target, and you are working on an existing component
of the system, then you might find yourself in a situation where you
need to restore the original files that existed prior to running the
``devtool deploy-target`` command. Because the ``devtool deploy-target``
command backs up any files it overwrites, you can use the
``devtool undeploy-target`` command to restore those files and remove
any other files the recipe deployed. Consider the following example::
$ devtool undeploy-target lighttpd root@192.168.7.2
If you have deployed
multiple applications, you can remove them all using the "-a" option
thus restoring the target device to its original state::
$ devtool undeploy-target -a root@192.168.7.2
Information about files deployed to
the target as well as any backed up files are stored on the target
itself. This storage, of course, requires some additional space on the
target machine.
.. note::
The ``devtool deploy-target`` and ``devtool undeploy-target`` commands do
not currently interact with any package management system on the target
device (e.g. RPM or OPKG). Consequently, you should not intermingle
``devtool deploy-target`` and package manager operations on the target
device. Doing so could result in a conflicting set of files.
Installing Additional Items Into the Extensible SDK
===================================================
Out of the box the extensible SDK typically only comes with a small
number of tools and libraries. A minimal SDK starts mostly empty and is
populated on-demand. Sometimes you must explicitly install extra items
into the SDK. If you need these extra items, you can first search for
the items using the ``devtool search`` command. For example, suppose you
need to link to libGL but you are not sure which recipe provides libGL.
You can use the following command to find out::
$ devtool search libGL mesa
A free implementation of the OpenGL API
Once you know the recipe
(i.e. ``mesa`` in this example), you can install it.
When using the extensible SDK directly in a Yocto build
-------------------------------------------------------
In this scenario, the Yocto build tooling, e.g. ``bitbake``
is directly accessible to build additional items, and it
can simply be executed directly::
$ bitbake mesa
$ bitbake build-sysroots
When using a standalone installer for the Extensible SDK
--------------------------------------------------------
::
$ devtool sdk-install mesa
By default, the ``devtool sdk-install`` command assumes
the item is available in pre-built form from your SDK provider. If the
item is not available and it is acceptable to build the item from
source, you can add the "-s" option as follows::
$ devtool sdk-install -s mesa
It is important to remember that building the item from source
takes significantly longer than installing the pre-built artifact. Also,
if there is no recipe for the item you want to add to the SDK, you must
instead add the item using the ``devtool add`` command.
Applying Updates to an Installed Extensible SDK
===============================================
If you are working with an installed extensible SDK that gets
occasionally updated (e.g. a third-party SDK), then you will need to
manually "pull down" the updates into the installed SDK.
To update your installed SDK, use ``devtool`` as follows::
$ devtool sdk-update
The previous command assumes your SDK provider has set the default update URL
for you through the :term:`SDK_UPDATE_URL` variable as described in the
":ref:`sdk-manual/appendix-customizing:Providing Updates to the Extensible SDK After Installation`"
section. If the SDK provider has not set that default URL, you need to
specify it yourself in the command as follows::
$ devtool sdk-update path_to_update_directory
.. note::
The URL needs to point specifically to a published SDK and not to an
SDK installer that you would download and install.
Creating a Derivative SDK With Additional Components
====================================================
You might need to produce an SDK that contains your own custom
libraries. A good example would be if you were a vendor with customers
that use your SDK to build their own platform-specific software and
those customers need an SDK that has custom libraries. In such a case,
you can produce a derivative SDK based on the currently installed SDK
fairly easily by following these steps:
#. If necessary, install an extensible SDK that you want to use as a
base for your derivative SDK.
#. Source the environment script for the SDK.
#. Add the extra libraries or other components you want by using the
``devtool add`` command.
#. Run the ``devtool build-sdk`` command.
The previous steps take the recipes added to the workspace and construct
a new SDK installer that contains those recipes and the resulting binary
artifacts. The recipes go into their own separate layer in the
constructed derivative SDK, which leaves the workspace clean and ready
for users to add their own recipes.
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