Complete Yocto mirror with license table for TQMa6UL (2038-compliance)
- 264 license table entries with exact download URLs (224/264 resolved) - Complete sources/ directory with all BitBake recipes - Build configuration: tqma6ul-multi-mba6ulx, spaetzle (musl) - Full traceability for Softwarefreigabeantrag - GCC 13.4.0, Linux 6.6.102, U-Boot 2023.04, musl 1.2.4 - License distribution: GPL-2.0 (24), MIT (23), GPL-2.0+ (18), BSD-3 (16)
This commit is contained in:
@@ -0,0 +1,408 @@
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.. SPDX-License-Identifier: CC-BY-2.5
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===================
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Hello World Example
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===================
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BitBake Hello World
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===================
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The simplest example commonly used to demonstrate any new programming
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language or tool is the "`Hello
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World <http://en.wikipedia.org/wiki/Hello_world_program>`__" example.
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This appendix demonstrates, in tutorial form, Hello World within the
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context of BitBake. The tutorial describes how to create a new project
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and the applicable metadata files necessary to allow BitBake to build
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it.
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Obtaining BitBake
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=================
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See the :ref:`bitbake-user-manual/bitbake-user-manual-intro:obtaining bitbake` section for
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information on how to obtain BitBake. Once you have the source code on
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your machine, the BitBake directory appears as follows::
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$ ls -al
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total 108
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drwxr-xr-x 9 fawkh 10000 4096 feb 24 12:10 .
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drwx------ 36 fawkh 10000 4096 mar 2 17:00 ..
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-rw-r--r-- 1 fawkh 10000 365 feb 24 12:10 AUTHORS
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drwxr-xr-x 2 fawkh 10000 4096 feb 24 12:10 bin
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-rw-r--r-- 1 fawkh 10000 16501 feb 24 12:10 ChangeLog
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drwxr-xr-x 2 fawkh 10000 4096 feb 24 12:10 classes
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drwxr-xr-x 2 fawkh 10000 4096 feb 24 12:10 conf
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drwxr-xr-x 5 fawkh 10000 4096 feb 24 12:10 contrib
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drwxr-xr-x 6 fawkh 10000 4096 feb 24 12:10 doc
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drwxr-xr-x 8 fawkh 10000 4096 mar 2 16:26 .git
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-rw-r--r-- 1 fawkh 10000 31 feb 24 12:10 .gitattributes
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-rw-r--r-- 1 fawkh 10000 392 feb 24 12:10 .gitignore
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drwxr-xr-x 13 fawkh 10000 4096 feb 24 12:11 lib
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-rw-r--r-- 1 fawkh 10000 1224 feb 24 12:10 LICENSE
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-rw-r--r-- 1 fawkh 10000 15394 feb 24 12:10 LICENSE.GPL-2.0-only
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-rw-r--r-- 1 fawkh 10000 1286 feb 24 12:10 LICENSE.MIT
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-rw-r--r-- 1 fawkh 10000 229 feb 24 12:10 MANIFEST.in
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-rw-r--r-- 1 fawkh 10000 2413 feb 24 12:10 README
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-rw-r--r-- 1 fawkh 10000 43 feb 24 12:10 toaster-requirements.txt
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-rw-r--r-- 1 fawkh 10000 2887 feb 24 12:10 TODO
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At this point, you should have BitBake cloned to a directory that
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matches the previous listing except for dates and user names.
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Setting Up the BitBake Environment
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==================================
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First, you need to be sure that you can run BitBake. Set your working
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directory to where your local BitBake files are and run the following
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command::
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$ ./bin/bitbake --version
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BitBake Build Tool Core version 2.3.1
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The console output tells you what version
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you are running.
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The recommended method to run BitBake is from a directory of your
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choice. To be able to run BitBake from any directory, you need to add
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the executable binary to your binary to your shell's environment
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``PATH`` variable. First, look at your current ``PATH`` variable by
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entering the following::
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$ echo $PATH
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Next, add the directory location
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for the BitBake binary to the ``PATH``. Here is an example that adds the
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``/home/scott-lenovo/bitbake/bin`` directory to the front of the
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``PATH`` variable::
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$ export PATH=/home/scott-lenovo/bitbake/bin:$PATH
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You should now be able to enter the ``bitbake`` command from the command
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line while working from any directory.
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The Hello World Example
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=======================
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The overall goal of this exercise is to build a complete "Hello World"
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example utilizing task and layer concepts. Because this is how modern
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projects such as OpenEmbedded and the Yocto Project utilize BitBake, the
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example provides an excellent starting point for understanding BitBake.
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To help you understand how to use BitBake to build targets, the example
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starts with nothing but the ``bitbake`` command, which causes BitBake to
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fail and report problems. The example progresses by adding pieces to the
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build to eventually conclude with a working, minimal "Hello World"
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example.
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While every attempt is made to explain what is happening during the
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example, the descriptions cannot cover everything. You can find further
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information throughout this manual. Also, you can actively participate
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in the :oe_lists:`/g/bitbake-devel`
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discussion mailing list about the BitBake build tool.
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.. note::
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This example was inspired by and drew heavily from
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`Mailing List post - The BitBake equivalent of "Hello, World!"
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<https://www.mail-archive.com/yocto@yoctoproject.org/msg09379.html>`_.
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As stated earlier, the goal of this example is to eventually compile
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"Hello World". However, it is unknown what BitBake needs and what you
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have to provide in order to achieve that goal. Recall that BitBake
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utilizes three types of metadata files:
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:ref:`bitbake-user-manual/bitbake-user-manual-intro:configuration files`,
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:ref:`bitbake-user-manual/bitbake-user-manual-intro:classes`, and
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:ref:`bitbake-user-manual/bitbake-user-manual-intro:recipes`.
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But where do they go? How does BitBake find
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them? BitBake's error messaging helps you answer these types of
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questions and helps you better understand exactly what is going on.
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Following is the complete "Hello World" example.
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#. **Create a Project Directory:** First, set up a directory for the
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"Hello World" project. Here is how you can do so in your home
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directory::
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$ mkdir ~/hello
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$ cd ~/hello
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This is the directory that
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BitBake will use to do all of its work. You can use this directory
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to keep all the metafiles needed by BitBake. Having a project
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directory is a good way to isolate your project.
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#. **Run BitBake:** At this point, you have nothing but a project
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directory. Run the ``bitbake`` command and see what it does::
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$ bitbake
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ERROR: The BBPATH variable is not set and bitbake did not find a conf/bblayers.conf file in the expected location.
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Maybe you accidentally invoked bitbake from the wrong directory?
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When you run BitBake, it begins looking for metadata files. The
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:term:`BBPATH` variable is what tells BitBake where
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to look for those files. :term:`BBPATH` is not set and you need to set
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it. Without :term:`BBPATH`, BitBake cannot find any configuration files
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(``.conf``) or recipe files (``.bb``) at all. BitBake also cannot
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find the ``bitbake.conf`` file.
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#. **Setting BBPATH:** For this example, you can set :term:`BBPATH` in
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the same manner that you set ``PATH`` earlier in the appendix. You
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should realize, though, that it is much more flexible to set the
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:term:`BBPATH` variable up in a configuration file for each project.
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From your shell, enter the following commands to set and export the
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:term:`BBPATH` variable::
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$ BBPATH="projectdirectory"
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$ export BBPATH
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Use your actual project directory in the command. BitBake uses that
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directory to find the metadata it needs for your project.
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.. note::
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When specifying your project directory, do not use the tilde
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("~") character as BitBake does not expand that character as the
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shell would.
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#. **Run BitBake:** Now that you have :term:`BBPATH` defined, run the
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``bitbake`` command again::
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$ bitbake
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ERROR: Unable to parse /home/scott-lenovo/bitbake/lib/bb/parse/__init__.py
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Traceback (most recent call last):
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File "/home/scott-lenovo/bitbake/lib/bb/parse/__init__.py", line 127, in resolve_file(fn='conf/bitbake.conf', d=<bb.data_smart.DataSmart object at 0x7f22919a3df0>):
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if not newfn:
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> raise IOError(errno.ENOENT, "file %s not found in %s" % (fn, bbpath))
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fn = newfn
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FileNotFoundError: [Errno 2] file conf/bitbake.conf not found in <projectdirectory>
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This sample output shows that BitBake could not find the
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``conf/bitbake.conf`` file in the project directory. This file is
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the first thing BitBake must find in order to build a target. And,
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since the project directory for this example is empty, you need to
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provide a ``conf/bitbake.conf`` file.
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#. **Creating conf/bitbake.conf:** The ``conf/bitbake.conf`` includes
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a number of configuration variables BitBake uses for metadata and
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recipe files. For this example, you need to create the file in your
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project directory and define some key BitBake variables. For more
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information on the ``bitbake.conf`` file, see
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https://git.openembedded.org/bitbake/tree/conf/bitbake.conf.
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Use the following commands to create the ``conf`` directory in the
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project directory::
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$ mkdir conf
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From within the ``conf`` directory,
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use some editor to create the ``bitbake.conf`` so that it contains
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the following::
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PN = "${@bb.parse.vars_from_file(d.getVar('FILE', False),d)[0] or 'defaultpkgname'}"
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TMPDIR = "${TOPDIR}/tmp"
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CACHE = "${TMPDIR}/cache"
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STAMP = "${TMPDIR}/${PN}/stamps"
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T = "${TMPDIR}/${PN}/work"
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B = "${TMPDIR}/${PN}"
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.. note::
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Without a value for :term:`PN`, the variables :term:`STAMP`, :term:`T`, and :term:`B`, prevent more
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than one recipe from working. You can fix this by either setting :term:`PN` to
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have a value similar to what OpenEmbedded and BitBake use in the default
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``bitbake.conf`` file (see previous example). Or, by manually updating each
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recipe to set :term:`PN`. You will also need to include :term:`PN` as part of the :term:`STAMP`,
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:term:`T`, and :term:`B` variable definitions in the ``local.conf`` file.
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The ``TMPDIR`` variable establishes a directory that BitBake uses
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for build output and intermediate files other than the cached
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information used by the
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:ref:`bitbake-user-manual/bitbake-user-manual-execution:setscene`
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process. Here, the ``TMPDIR`` directory is set to ``hello/tmp``.
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.. tip::
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You can always safely delete the tmp directory in order to rebuild a
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BitBake target. The build process creates the directory for you when you
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run BitBake.
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For information about each of the other variables defined in this
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example, check :term:`PN`, :term:`TOPDIR`, :term:`CACHE`, :term:`STAMP`,
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:term:`T` or :term:`B` to take you to the definitions in the
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glossary.
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#. **Run BitBake:** After making sure that the ``conf/bitbake.conf`` file
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exists, you can run the ``bitbake`` command again::
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$ bitbake
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ERROR: Unable to parse /home/scott-lenovo/bitbake/lib/bb/parse/parse_py/BBHandler.py
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Traceback (most recent call last):
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File "/home/scott-lenovo/bitbake/lib/bb/parse/parse_py/BBHandler.py", line 67, in inherit(files=['base'], fn='configuration INHERITs', lineno=0, d=<bb.data_smart.DataSmart object at 0x7fab6815edf0>):
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if not os.path.exists(file):
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> raise ParseError("Could not inherit file %s" % (file), fn, lineno)
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bb.parse.ParseError: ParseError in configuration INHERITs: Could not inherit file classes/base.bbclass
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In the sample output,
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BitBake could not find the ``classes/base.bbclass`` file. You need
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to create that file next.
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#. **Creating classes/base.bbclass:** BitBake uses class files to
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provide common code and functionality. The minimally required class
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for BitBake is the ``classes/base.bbclass`` file. The ``base`` class
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is implicitly inherited by every recipe. BitBake looks for the class
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in the ``classes`` directory of the project (i.e ``hello/classes``
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in this example).
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Create the ``classes`` directory as follows::
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$ cd $HOME/hello
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$ mkdir classes
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Move to the ``classes`` directory and then create the
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``base.bbclass`` file by inserting this single line::
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addtask build
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The minimal task that BitBake runs is the ``do_build`` task. This is
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all the example needs in order to build the project. Of course, the
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``base.bbclass`` can have much more depending on which build
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environments BitBake is supporting.
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#. **Run BitBake:** After making sure that the ``classes/base.bbclass``
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file exists, you can run the ``bitbake`` command again::
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$ bitbake
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Nothing to do. Use 'bitbake world' to build everything, or run 'bitbake --help' for usage information.
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BitBake is finally reporting
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no errors. However, you can see that it really does not have
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anything to do. You need to create a recipe that gives BitBake
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something to do.
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#. **Creating a Layer:** While it is not really necessary for such a
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small example, it is good practice to create a layer in which to
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keep your code separate from the general metadata used by BitBake.
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Thus, this example creates and uses a layer called "mylayer".
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.. note::
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You can find additional information on layers in the
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":ref:`bitbake-user-manual/bitbake-user-manual-intro:Layers`" section.
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Minimally, you need a recipe file and a layer configuration file in
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your layer. The configuration file needs to be in the ``conf``
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directory inside the layer. Use these commands to set up the layer
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and the ``conf`` directory::
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$ cd $HOME
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$ mkdir mylayer
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$ cd mylayer
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$ mkdir conf
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Move to the ``conf`` directory and create a ``layer.conf`` file that has the
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following::
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BBPATH .= ":${LAYERDIR}"
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BBFILES += "${LAYERDIR}/*.bb"
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BBFILE_COLLECTIONS += "mylayer"
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BBFILE_PATTERN_mylayer := "^${LAYERDIR_RE}/"
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LAYERSERIES_CORENAMES = "hello_world_example"
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LAYERSERIES_COMPAT_mylayer = "hello_world_example"
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For information on these variables, click on :term:`BBFILES`,
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:term:`LAYERDIR`, :term:`BBFILE_COLLECTIONS`, :term:`BBFILE_PATTERN_mylayer <BBFILE_PATTERN>`
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or :term:`LAYERSERIES_COMPAT` to go to the definitions in the glossary.
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.. note::
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We are setting both ``LAYERSERIES_CORENAMES`` and :term:`LAYERSERIES_COMPAT` in this particular case, because we
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are using bitbake without OpenEmbedded.
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You should usually just use :term:`LAYERSERIES_COMPAT` to specify the OE-Core versions for which your layer
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is compatible, and add the meta-openembedded layer to your project.
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You need to create the recipe file next. Inside your layer at the
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top-level, use an editor and create a recipe file named
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``printhello.bb`` that has the following::
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DESCRIPTION = "Prints Hello World"
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PN = 'printhello'
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PV = '1'
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python do_build() {
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bb.plain("********************");
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bb.plain("* *");
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bb.plain("* Hello, World! *");
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bb.plain("* *");
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bb.plain("********************");
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}
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The recipe file simply provides
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a description of the recipe, the name, version, and the ``do_build``
|
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task, which prints out "Hello World" to the console. For more
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information on :term:`DESCRIPTION`, :term:`PN` or :term:`PV`
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follow the links to the glossary.
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#. **Run BitBake With a Target:** Now that a BitBake target exists, run
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||||
the command and provide that target::
|
||||
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$ cd $HOME/hello
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$ bitbake printhello
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ERROR: no recipe files to build, check your BBPATH and BBFILES?
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||||
Summary: There was 1 ERROR message shown, returning a non-zero exit code.
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||||
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We have created the layer with the recipe and
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||||
the layer configuration file but it still seems that BitBake cannot
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||||
find the recipe. BitBake needs a ``conf/bblayers.conf`` that lists
|
||||
the layers for the project. Without this file, BitBake cannot find
|
||||
the recipe.
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||||
|
||||
#. **Creating conf/bblayers.conf:** BitBake uses the
|
||||
``conf/bblayers.conf`` file to locate layers needed for the project.
|
||||
This file must reside in the ``conf`` directory of the project (i.e.
|
||||
``hello/conf`` for this example).
|
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|
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Set your working directory to the ``hello/conf`` directory and then
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create the ``bblayers.conf`` file so that it contains the following::
|
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BBLAYERS ?= " \
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/home/<you>/mylayer \
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"
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||||
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||||
You need to provide your own information for ``you`` in the file.
|
||||
|
||||
#. **Run BitBake With a Target:** Now that you have supplied the
|
||||
``bblayers.conf`` file, run the ``bitbake`` command and provide the
|
||||
target::
|
||||
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||||
$ bitbake printhello
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Loading cache: 100% |
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Loaded 0 entries from dependency cache.
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Parsing recipes: 100% |##################################################################################|
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Parsing of 1 .bb files complete (0 cached, 1 parsed). 1 targets, 0 skipped, 0 masked, 0 errors.
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NOTE: Resolving any missing task queue dependencies
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Initialising tasks: 100% |###############################################################################|
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NOTE: No setscene tasks
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||||
NOTE: Executing Tasks
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********************
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* *
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* Hello, World! *
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* *
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********************
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NOTE: Tasks Summary: Attempted 1 tasks of which 0 didn't need to be rerun and all succeeded.
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||||
|
||||
.. note::
|
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After the first execution, re-running bitbake printhello again will not
|
||||
result in a BitBake run that prints the same console output. The reason
|
||||
for this is that the first time the printhello.bb recipe's do_build task
|
||||
executes successfully, BitBake writes a stamp file for the task. Thus,
|
||||
the next time you attempt to run the task using that same bitbake
|
||||
command, BitBake notices the stamp and therefore determines that the task
|
||||
does not need to be re-run. If you delete the tmp directory or run
|
||||
bitbake -c clean printhello and then re-run the build, the "Hello,
|
||||
World!" message will be printed again.
|
||||
Reference in New Issue
Block a user