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diff --git a/import-layers/yocto-poky/bitbake/doc/bitbake-user-manual/bitbake-user-manual-hello.xml b/import-layers/yocto-poky/bitbake/doc/bitbake-user-manual/bitbake-user-manual-hello.xml new file mode 100644 index 000000000..f6d82b4f3 --- /dev/null +++ b/import-layers/yocto-poky/bitbake/doc/bitbake-user-manual/bitbake-user-manual-hello.xml @@ -0,0 +1,505 @@ +<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" +"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<appendix id='hello-world-example'> + <title>Hello World Example</title> + + <section id='bitbake-hello-world'> + <title>BitBake Hello World</title> + + <para> + The simplest example commonly used to demonstrate any new + programming language or tool is the + "<ulink url="http://en.wikipedia.org/wiki/Hello_world_program">Hello World</ulink>" + example. + This appendix demonstrates, in tutorial form, Hello + World within the context of BitBake. + The tutorial describes how to create a new project + and the applicable metadata files necessary to allow + BitBake to build it. + </para> + </section> + + <section id='example-obtaining-bitbake'> + <title>Obtaining BitBake</title> + + <para> + See the + "<link linkend='obtaining-bitbake'>Obtaining BitBake</link>" + section for information on how to obtain BitBake. + Once you have the source code on your machine, the BitBake directory + appears as follows: + <literallayout class='monospaced'> + $ ls -al + total 100 + drwxrwxr-x. 9 wmat wmat 4096 Jan 31 13:44 . + drwxrwxr-x. 3 wmat wmat 4096 Feb 4 10:45 .. + -rw-rw-r--. 1 wmat wmat 365 Nov 26 04:55 AUTHORS + drwxrwxr-x. 2 wmat wmat 4096 Nov 26 04:55 bin + drwxrwxr-x. 4 wmat wmat 4096 Jan 31 13:44 build + -rw-rw-r--. 1 wmat wmat 16501 Nov 26 04:55 ChangeLog + drwxrwxr-x. 2 wmat wmat 4096 Nov 26 04:55 classes + drwxrwxr-x. 2 wmat wmat 4096 Nov 26 04:55 conf + drwxrwxr-x. 3 wmat wmat 4096 Nov 26 04:55 contrib + -rw-rw-r--. 1 wmat wmat 17987 Nov 26 04:55 COPYING + drwxrwxr-x. 3 wmat wmat 4096 Nov 26 04:55 doc + -rw-rw-r--. 1 wmat wmat 69 Nov 26 04:55 .gitignore + -rw-rw-r--. 1 wmat wmat 849 Nov 26 04:55 HEADER + drwxrwxr-x. 5 wmat wmat 4096 Jan 31 13:44 lib + -rw-rw-r--. 1 wmat wmat 195 Nov 26 04:55 MANIFEST.in + -rw-rw-r--. 1 wmat wmat 2887 Nov 26 04:55 TODO + </literallayout> + </para> + + <para> + At this point, you should have BitBake cloned to + a directory that matches the previous listing except for + dates and user names. + </para> + </section> + + <section id='setting-up-the-bitbake-environment'> + <title>Setting Up the BitBake Environment</title> + + <para> + First, you need to be sure that you can run BitBake. + Set your working directory to where your local BitBake + files are and run the following command: + <literallayout class='monospaced'> + $ ./bin/bitbake --version + BitBake Build Tool Core version 1.23.0, bitbake version 1.23.0 + </literallayout> + The console output tells you what version you are running. + </para> + + <para> + The recommended method to run BitBake is from a directory of your + choice. + To be able to run BitBake from any directory, you need to add the + executable binary to your binary to your shell's environment + <filename>PATH</filename> variable. + First, look at your current <filename>PATH</filename> variable + by entering the following: + <literallayout class='monospaced'> + $ echo $PATH + </literallayout> + Next, add the directory location for the BitBake binary to the + <filename>PATH</filename>. + Here is an example that adds the + <filename>/home/scott-lenovo/bitbake/bin</filename> directory + to the front of the <filename>PATH</filename> variable: + <literallayout class='monospaced'> + $ export PATH=/home/scott-lenovo/bitbake/bin:$PATH + </literallayout> + You should now be able to enter the <filename>bitbake</filename> + command from the command line while working from any directory. + </para> + </section> + + <section id='the-hello-world-example'> + <title>The Hello World Example</title> + + <para> + The overall goal of this exercise is to build a + complete "Hello World" example utilizing task and layer + concepts. + Because this is how modern projects such as OpenEmbedded and + the Yocto Project utilize BitBake, the example + provides an excellent starting point for understanding + BitBake. + </para> + + <para> + To help you understand how to use BitBake to build targets, + the example starts with nothing but the <filename>bitbake</filename> + command, which causes BitBake to fail and report problems. + The example progresses by adding pieces to the build to + eventually conclude with a working, minimal "Hello World" + example. + </para> + + <para> + While every attempt is made to explain what is happening during + the example, the descriptions cannot cover everything. + You can find further information throughout this manual. + Also, you can actively participate in the + <ulink url='http://lists.openembedded.org/mailman/listinfo/bitbake-devel'></ulink> + discussion mailing list about the BitBake build tool. + </para> + + <note> + This example was inspired by and drew heavily from these sources: + <itemizedlist> + <listitem><para> + <ulink url="http://www.mail-archive.com/yocto@yoctoproject.org/msg09379.html">Mailing List post - The BitBake equivalent of "Hello, World!"</ulink> + </para></listitem> + <listitem><para> + <ulink url="http://hambedded.org/blog/2012/11/24/from-bitbake-hello-world-to-an-image/">Hambedded Linux blog post - From Bitbake Hello World to an Image</ulink> + </para></listitem> + </itemizedlist> + </note> + + <para> + As stated earlier, the goal of this example + is to eventually compile "Hello World". + However, it is unknown what BitBake needs and what you have + to provide in order to achieve that goal. + Recall that BitBake utilizes three types of metadata files: + <link linkend='configuration-files'>Configuration Files</link>, + <link linkend='classes'>Classes</link>, and + <link linkend='recipes'>Recipes</link>. + But where do they go? + How does BitBake find them? + BitBake's error messaging helps you answer these types of questions + and helps you better understand exactly what is going on. + </para> + + <para> + Following is the complete "Hello World" example. + </para> + + <orderedlist> + <listitem><para><emphasis>Create a Project Directory:</emphasis> + First, set up a directory for the "Hello World" project. + Here is how you can do so in your home directory: + <literallayout class='monospaced'> + $ mkdir ~/hello + $ cd ~/hello + </literallayout> + This is the directory that BitBake will use to do all of + its work. + You can use this directory to keep all the metafiles needed + by BitBake. + Having a project directory is a good way to isolate your + project. + </para></listitem> + <listitem><para><emphasis>Run Bitbake:</emphasis> + At this point, you have nothing but a project directory. + Run the <filename>bitbake</filename> command and see what + it does: + <literallayout class='monospaced'> + $ bitbake + The BBPATH variable is not set and bitbake did not + find a conf/bblayers.conf file in the expected location. + Maybe you accidentally invoked bitbake from the wrong directory? + DEBUG: Removed the following variables from the environment: + GNOME_DESKTOP_SESSION_ID, XDG_CURRENT_DESKTOP, + GNOME_KEYRING_CONTROL, DISPLAY, SSH_AGENT_PID, LANG, no_proxy, + XDG_SESSION_PATH, XAUTHORITY, SESSION_MANAGER, SHLVL, + MANDATORY_PATH, COMPIZ_CONFIG_PROFILE, WINDOWID, EDITOR, + GPG_AGENT_INFO, SSH_AUTH_SOCK, GDMSESSION, GNOME_KEYRING_PID, + XDG_SEAT_PATH, XDG_CONFIG_DIRS, LESSOPEN, DBUS_SESSION_BUS_ADDRESS, + _, XDG_SESSION_COOKIE, DESKTOP_SESSION, LESSCLOSE, DEFAULTS_PATH, + UBUNTU_MENUPROXY, OLDPWD, XDG_DATA_DIRS, COLORTERM, LS_COLORS + </literallayout> + The majority of this output is specific to environment variables + that are not directly relevant to BitBake. + However, the very first message regarding the + <filename>BBPATH</filename> variable and the + <filename>conf/bblayers.conf</filename> file + is relevant.</para> + <para> + When you run BitBake, it begins looking for metadata files. + The + <link linkend='var-BBPATH'><filename>BBPATH</filename></link> + variable is what tells BitBake where to look for those files. + <filename>BBPATH</filename> is not set and you need to set it. + Without <filename>BBPATH</filename>, Bitbake cannot + find any configuration files (<filename>.conf</filename>) + or recipe files (<filename>.bb</filename>) at all. + BitBake also cannot find the <filename>bitbake.conf</filename> + file. + </para></listitem> + <listitem><para><emphasis>Setting <filename>BBPATH</filename>:</emphasis> + For this example, you can set <filename>BBPATH</filename> + in the same manner that you set <filename>PATH</filename> + earlier in the appendix. + You should realize, though, that it is much more flexible to set the + <filename>BBPATH</filename> variable up in a configuration + file for each project.</para> + <para>From your shell, enter the following commands to set and + export the <filename>BBPATH</filename> variable: + <literallayout class='monospaced'> + $ BBPATH="<replaceable>projectdirectory</replaceable>" + $ export BBPATH + </literallayout> + Use your actual project directory in the command. + BitBake uses that directory to find the metadata it needs for + your project. + <note> + When specifying your project directory, do not use the + tilde ("~") character as BitBake does not expand that character + as the shell would. + </note> + </para></listitem> + <listitem><para><emphasis>Run Bitbake:</emphasis> + Now that you have <filename>BBPATH</filename> defined, run + the <filename>bitbake</filename> command again: + <literallayout class='monospaced'> + $ bitbake + ERROR: Traceback (most recent call last): + File "/home/scott-lenovo/bitbake/lib/bb/cookerdata.py", line 163, in wrapped + return func(fn, *args) + File "/home/scott-lenovo/bitbake/lib/bb/cookerdata.py", line 173, in parse_config_file + return bb.parse.handle(fn, data, include) + File "/home/scott-lenovo/bitbake/lib/bb/parse/__init__.py", line 99, in handle + return h['handle'](fn, data, include) + File "/home/scott-lenovo/bitbake/lib/bb/parse/parse_py/ConfHandler.py", line 120, in handle + abs_fn = resolve_file(fn, data) + File "/home/scott-lenovo/bitbake/lib/bb/parse/__init__.py", line 117, in resolve_file + raise IOError("file %s not found in %s" % (fn, bbpath)) + IOError: file conf/bitbake.conf not found in /home/scott-lenovo/hello + + ERROR: Unable to parse conf/bitbake.conf: file conf/bitbake.conf not found in /home/scott-lenovo/hello + </literallayout> + This sample output shows that BitBake could not find the + <filename>conf/bitbake.conf</filename> file in the project + directory. + This file is the first thing BitBake must find in order + to build a target. + And, since the project directory for this example is + empty, you need to provide a <filename>conf/bitbake.conf</filename> + file. + </para></listitem> + <listitem><para><emphasis>Creating <filename>conf/bitbake.conf</filename>:</emphasis> + The <filename>conf/bitbake.conf</filename> includes a number of + configuration variables BitBake uses for metadata and recipe + files. + For this example, you need to create the file in your project directory + and define some key BitBake variables. + For more information on the <filename>bitbake.conf</filename>, + see + <ulink url='http://hambedded.org/blog/2012/11/24/from-bitbake-hello-world-to-an-image/#an-overview-of-bitbakeconf'></ulink> + </para> + <para>Use the following commands to create the <filename>conf</filename> + directory in the project directory: + <literallayout class='monospaced'> + $ mkdir conf + </literallayout> + From within the <filename>conf</filename> directory, use + some editor to create the <filename>bitbake.conf</filename> + so that it contains the following: + <literallayout class='monospaced'> + TMPDIR = "${<link linkend='var-TOPDIR'>TOPDIR</link>}/tmp" + <link linkend='var-CACHE'>CACHE</link> = "${TMPDIR}/cache" + <link linkend='var-STAMP'>STAMP</link> = "${TMPDIR}/stamps" + <link linkend='var-T'>T</link> = "${TMPDIR}/work" + <link linkend='var-B'>B</link> = "${TMPDIR}" + </literallayout> + The <filename>TMPDIR</filename> variable establishes a directory + that BitBake uses for build output and intermediate files (other + than the cached information used by the + <link linkend='setscene'>Setscene</link> process. + Here, the <filename>TMPDIR</filename> directory is set to + <filename>hello/tmp</filename>. + <note><title>Tip</title> + You can always safely delete the <filename>tmp</filename> + directory in order to rebuild a BitBake target. + The build process creates the directory for you + when you run BitBake. + </note></para> + <para>For information about each of the other variables defined in this + example, click on the links to take you to the definitions in + the glossary. + </para></listitem> + <listitem><para><emphasis>Run Bitbake:</emphasis> + After making sure that the <filename>conf/bitbake.conf</filename> + file exists, you can run the <filename>bitbake</filename> + command again: + <literallayout class='monospaced'> +$ bitbake +ERROR: Traceback (most recent call last): + File "/home/scott-lenovo/bitbake/lib/bb/cookerdata.py", line 163, in wrapped + return func(fn, *args) + File "/home/scott-lenovo/bitbake/lib/bb/cookerdata.py", line 177, in _inherit + bb.parse.BBHandler.inherit(bbclass, "configuration INHERITs", 0, data) + File "/home/scott-lenovo/bitbake/lib/bb/parse/parse_py/BBHandler.py", line 92, in inherit + include(fn, file, lineno, d, "inherit") + File "/home/scott-lenovo/bitbake/lib/bb/parse/parse_py/ConfHandler.py", line 100, in include + raise ParseError("Could not %(error_out)s file %(fn)s" % vars(), oldfn, lineno) +ParseError: ParseError in configuration INHERITs: Could not inherit file classes/base.bbclass + +ERROR: Unable to parse base: ParseError in configuration INHERITs: Could not inherit file classes/base.bbclass + </literallayout> + In the sample output, BitBake could not find the + <filename>classes/base.bbclass</filename> file. + You need to create that file next. + </para></listitem> + <listitem><para><emphasis>Creating <filename>classes/base.bbclass</filename>:</emphasis> + BitBake uses class files to provide common code and functionality. + The minimally required class for BitBake is the + <filename>classes/base.bbclass</filename> file. + The <filename>base</filename> class is implicitly inherited by + every recipe. + BitBake looks for the class in the <filename>classes</filename> + directory of the project (i.e <filename>hello/classes</filename> + in this example). + </para> + <para>Create the <filename>classes</filename> directory as follows: + <literallayout class='monospaced'> + $ cd $HOME/hello + $ mkdir classes + </literallayout> + Move to the <filename>classes</filename> directory and then + create the <filename>base.bbclass</filename> file by inserting + this single line: + <literallayout class='monospaced'> + addtask build + </literallayout> + The minimal task that BitBake runs is the + <filename>do_build</filename> task. + This is all the example needs in order to build the project. + Of course, the <filename>base.bbclass</filename> can have much + more depending on which build environments BitBake is + supporting. + For more information on the <filename>base.bbclass</filename> file, + you can look at + <ulink url='http://hambedded.org/blog/2012/11/24/from-bitbake-hello-world-to-an-image/#tasks'></ulink>. + </para></listitem> + <listitem><para><emphasis>Run Bitbake:</emphasis> + After making sure that the <filename>classes/base.bbclass</filename> + file exists, you can run the <filename>bitbake</filename> + command again: + <literallayout class='monospaced'> + $ bitbake + Nothing to do. Use 'bitbake world' to build everything, or run 'bitbake --help' for usage information. + </literallayout> + BitBake is finally reporting no errors. + However, you can see that it really does not have anything + to do. + You need to create a recipe that gives BitBake something to do. + </para></listitem> + <listitem><para><emphasis>Creating a Layer:</emphasis> + While it is not really necessary for such a small example, + it is good practice to create a layer in which to keep your + code separate from the general metadata used by BitBake. + Thus, this example creates and uses a layer called "mylayer". + <note> + You can find additional information on adding a layer at + <ulink url='http://hambedded.org/blog/2012/11/24/from-bitbake-hello-world-to-an-image/#adding-an-example-layer'></ulink>. + </note> + </para> + <para>Minimally, you need a recipe file and a layer configuration + file in your layer. + The configuration file needs to be in the <filename>conf</filename> + directory inside the layer. + Use these commands to set up the layer and the <filename>conf</filename> + directory: + <literallayout class='monospaced'> + $ cd $HOME + $ mkdir mylayer + $ cd mylayer + $ mkdir conf + </literallayout> + Move to the <filename>conf</filename> directory and create a + <filename>layer.conf</filename> file that has the following: + <literallayout class='monospaced'> + BBPATH .= ":${<link linkend='var-LAYERDIR'>LAYERDIR</link>}" + + <link linkend='var-BBFILES'>BBFILES</link> += "${LAYERDIR}/*.bb" + + <link linkend='var-BBFILE_COLLECTIONS'>BBFILE_COLLECTIONS</link> += "mylayer" + <link linkend='var-BBFILE_PATTERN'>BBFILE_PATTERN_mylayer</link> := "^${LAYERDIR}/" + </literallayout> + For information on these variables, click the links + to go to the definitions in the glossary.</para> + <para>You need to create the recipe file next. + Inside your layer at the top-level, use an editor and create + a recipe file named <filename>printhello.bb</filename> that + has the following: + <literallayout class='monospaced'> + <link linkend='var-DESCRIPTION'>DESCRIPTION</link> = "Prints Hello World" + <link linkend='var-PN'>PN</link> = 'printhello' + <link linkend='var-PV'>PV</link> = '1' + + python do_build() { + bb.plain("********************"); + bb.plain("* *"); + bb.plain("* Hello, World! *"); + bb.plain("* *"); + bb.plain("********************"); + } + </literallayout> + The recipe file simply provides a description of the + recipe, the name, version, and the <filename>do_build</filename> + task, which prints out "Hello World" to the console. + For more information on these variables, follow the links + to the glossary. + </para></listitem> + <listitem><para><emphasis>Run Bitbake With a Target:</emphasis> + Now that a BitBake target exists, run the command and provide + that target: + <literallayout class='monospaced'> + $ cd $HOME/hello + $ bitbake printhello + ERROR: no recipe files to build, check your BBPATH and BBFILES? + + Summary: There was 1 ERROR message shown, returning a non-zero exit code. + </literallayout> + We have created the layer with the recipe and the layer + configuration file but it still seems that BitBake cannot + find the recipe. + BitBake needs a <filename>conf/bblayers.conf</filename> that + lists the layers for the project. + Without this file, BitBake cannot find the recipe. + </para></listitem> + <listitem><para><emphasis>Creating <filename>conf/bblayers.conf</filename>:</emphasis> + BitBake uses the <filename>conf/bblayers.conf</filename> file + to locate layers needed for the project. + This file must reside in the <filename>conf</filename> directory + of the project (i.e. <filename>hello/conf</filename> for this + example).</para> + <para>Set your working directory to the <filename>hello/conf</filename> + directory and then create the <filename>bblayers.conf</filename> + file so that it contains the following: + <literallayout class='monospaced'> + BBLAYERS ?= " \ + /home/<you>/mylayer \ + " + </literallayout> + You need to provide your own information for + <filename>you</filename> in the file. + </para></listitem> + <listitem><para><emphasis>Run Bitbake With a Target:</emphasis> + Now that you have supplied the <filename>bblayers.conf</filename> + file, run the <filename>bitbake</filename> command and provide + the target: + <literallayout class='monospaced'> + $ bitbake printhello + Parsing recipes: 100% |##################################################################################| + Time: 00:00:00 + Parsing of 1 .bb files complete (0 cached, 1 parsed). 1 targets, 0 skipped, 0 masked, 0 errors. + NOTE: Resolving any missing task queue dependencies + NOTE: Preparing RunQueue + NOTE: Executing RunQueue Tasks + ******************** + * * + * Hello, World! * + * * + ******************** + NOTE: Tasks Summary: Attempted 1 tasks of which 0 didn't need to be rerun and all succeeded. + </literallayout> + BitBake finds the <filename>printhello</filename> recipe and + successfully runs the task. + <note> + After the first execution, re-running + <filename>bitbake printhello</filename> again will not + result in a BitBake run that prints the same console + output. + The reason for this is that the first time the + <filename>printhello.bb</filename> recipe's + <filename>do_build</filename> task executes + successfully, BitBake writes a stamp file for the task. + Thus, the next time you attempt to run the task + using that same <filename>bitbake</filename> command, + BitBake notices the stamp and therefore determines + that the task does not need to be re-run. + If you delete the <filename>tmp</filename> directory + or run <filename>bitbake -c clean printhello</filename> + and then re-run the build, the "Hello, World!" message will + be printed again. + </note> + </para></listitem> + </orderedlist> + </section> +</appendix> |
