diff options
author | Scott Rifenbark <scott.m.rifenbark@intel.com> | 2014-02-14 13:55:42 -0600 |
---|---|---|
committer | Richard Purdie <richard.purdie@linuxfoundation.org> | 2014-03-09 18:59:03 -0700 |
commit | 0c5bf41968eddb8959aa4c4815a6a142cf4e87a6 (patch) | |
tree | 0992c097dd01e39df619915f8f127542cc4e3728 /bitbake/doc/user-manual/user-manual-execution.xml | |
parent | 013c9d918170a821ecbb1e9b86cc1861b7785b0f (diff) | |
download | poky-0c5bf41968eddb8959aa4c4815a6a142cf4e87a6.tar.gz |
bitbake: user-manual-execution.xml: Draft of "Execution" chapter
This is a rough draft of the chapter. Major sections are in
place. We need to scrub content now.
Seems like the discussion of BBFILES fit better in this
execution flow chapter. So, I moved it above the parsing
section.
(Bitbake rev: 6c4c6fb689b88dbefe63f0062b78d8403fb80d41)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'bitbake/doc/user-manual/user-manual-execution.xml')
-rw-r--r-- | bitbake/doc/user-manual/user-manual-execution.xml | 1303 |
1 files changed, 633 insertions, 670 deletions
diff --git a/bitbake/doc/user-manual/user-manual-execution.xml b/bitbake/doc/user-manual/user-manual-execution.xml index 365392dbff..aa345de698 100644 --- a/bitbake/doc/user-manual/user-manual-execution.xml +++ b/bitbake/doc/user-manual/user-manual-execution.xml | |||
@@ -5,686 +5,649 @@ | |||
5 | <title>Execution</title> | 5 | <title>Execution</title> |
6 | 6 | ||
7 | <para> | 7 | <para> |
8 | Tasks can either be a shell task or a Python task. | 8 | The primary purpose for running BitBake is to produce an |
9 | For shell tasks, BitBake writes a shell script to | 9 | image, which can be a kernel or a software development kit (SDK). |
10 | <filename>${WORKDIR}/temp/run.do_taskname.pid</filename> | 10 | Of course, you can execute the <filename>bitbake</filename> |
11 | and then executes the script. | 11 | command with options that cause it to execute single tasks, |
12 | The generated shell script contains all the exported variables, | 12 | compile single recipe files, capture or clear data, or simply |
13 | and the shell functions with all variables expanded. | 13 | return information about the execution environment. |
14 | Output from the shell script goes to the file | ||
15 | <filename>${WORKDIR}/temp/log.do_taskname.pid</filename>. | ||
16 | Looking at the expanded shell functions in the run file and | ||
17 | the output in the log files is a useful debugging technique. | ||
18 | </para> | 14 | </para> |
19 | 15 | ||
20 | <para> | 16 | <para> |
21 | For Python tasks, BitBake executes the task internally and logs | 17 | This chapter describes BitBake's execution process from start |
22 | information to the controlling terminal. | 18 | to finish when you use it to create an image. |
23 | Future versions of BitBake will write the functions to files | 19 | The execution process is launched using the following command |
24 | similar to the way shell tasks are handled. | 20 | form: |
25 | Logging will be handled in a way similar to shell tasks as well. | 21 | <literallayout class='monospaced'> |
22 | $ bitbake <target> | ||
23 | </literallayout> | ||
24 | For information on the BitBake command and its options, | ||
25 | see the | ||
26 | "<link linkend='user-manual-command'>BitBake Command</link> | ||
27 | chapter. | ||
26 | </para> | 28 | </para> |
27 | 29 | ||
28 | <para> | 30 | <section id='parsing-the-base-configuration-metadata'> |
29 | Once all the tasks have been completed BitBake exits. | 31 | <title>Parsing the Base Configuration Metadata</title> |
30 | </para> | 32 | |
33 | <para> | ||
34 | The first thing BitBake does is parse base configuration | ||
35 | metadata. | ||
36 | Base configuration metadata consists of the | ||
37 | <filename>bblayers.conf</filename> file to determine what | ||
38 | layers BitBake needs to recognize, all necessary | ||
39 | <filename>layer.conf</filename> files (one from each layer), | ||
40 | and <filename>bitbake.conf</filename>. | ||
41 | </para> | ||
42 | |||
43 | <para> | ||
44 | The <filename>bitbake.conf</filename> file resides in the | ||
45 | <filename>conf</filename> directory, which must be listed in | ||
46 | <link linkend='var-BBPATH'><filename>BBPATH</filename></link>. | ||
47 | This configuratoin file lists and includes other configuration | ||
48 | files from the <filename>conf</filename> directory below the | ||
49 | directories listed in <filename>BBPATH</filename>. | ||
50 | In general, the most important of these included | ||
51 | configuration files from a user's perspective | ||
52 | is <filename>local.conf</filename>, which contains the user's | ||
53 | customized settings for the build environment. | ||
54 | </para> | ||
55 | |||
56 | <para> | ||
57 | Other notable configuration files are the distribution configuration | ||
58 | file and the machine configuration file. | ||
59 | These configuration files are normally identified by | ||
60 | variables unique to the build systems using BitBake. | ||
61 | For example, the Yocto Project uses the | ||
62 | <filename>DISTRO</filename> and <filename>MACHINE</filename> | ||
63 | variables, respectively. | ||
64 | </para> | ||
65 | |||
66 | <para> | ||
67 | Prior to parsing configuration files, Bitbake looks | ||
68 | at certain variables, including: | ||
69 | <itemizedlist> | ||
70 | <listitem><para><link linkend='var-BB_ENV_WHITELIST'><filename>BB_ENV_WHITELIST</filename></link></para></listitem> | ||
71 | <listitem><para><link linkend='var-BB_PRESERVE_ENV'><filename>BB_PRESERVE_ENV</filename></link></para></listitem> | ||
72 | <listitem><para><link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link></para></listitem> | ||
73 | <listitem><para><link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link></para></listitem> | ||
74 | <listitem><para><link linkend='var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></link></para></listitem> | ||
75 | <listitem><para><link linkend='var-PREFERRED_PROVIDERS'><filename>PREFERRED_PROVIDERS</filename></link></para></listitem> | ||
76 | </itemizedlist> | ||
77 | </para> | ||
78 | |||
79 | <para> | ||
80 | The base configuration metadata is global | ||
81 | and therefore affects all packages and tasks that are executed. | ||
82 | </para> | ||
83 | |||
84 | <para> | ||
85 | BitBake first searches the current working directory for an | ||
86 | optional <filename>conf/bblayers.conf</filename> configuration file. | ||
87 | This file is expected to contain a | ||
88 | <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link> | ||
89 | variable that is a space delimited list of 'layer' directories. | ||
90 | </para> | ||
91 | |||
92 | <para> | ||
93 | For each directory (layer) in this list, a <filename>conf/layer.conf</filename> | ||
94 | file is searched for and parsed with the | ||
95 | <link linkend='var-LAYERDIR'><filename>LAYERDIR</filename></link> | ||
96 | variable being set to the directory where the layer was found. | ||
97 | The idea is these files automatically setup | ||
98 | <link linkend='var-BBPATH'><filename>BBPATH</filename></link> | ||
99 | and other variables correctly for a given build directory. | ||
100 | </para> | ||
101 | |||
102 | <para> | ||
103 | BitBake then expects to find the <filename>conf/bitbake.conf</filename> | ||
104 | file somewhere in the user-specified <filename>BBPATH</filename>. | ||
105 | That configuration file generally has include directives to pull | ||
106 | in any other metadata such as files specific to the architecture, | ||
107 | the machine, the local environment, and so forth. | ||
108 | </para> | ||
109 | |||
110 | <para> | ||
111 | Only variable definitions and include directives are allowed | ||
112 | in <filename>.conf</filename> files. | ||
113 | The following variables include: | ||
114 | <itemizedlist> | ||
115 | <listitem><para> | ||
116 | <link linkend='var-BITBAKE_UI'><filename>BITBAKE_UI</filename></link> | ||
117 | </para></listitem> | ||
118 | <listitem><para> | ||
119 | <link linkend='var-BBDEBUG'><filename>BBDEBUG</filename></link> | ||
120 | </para></listitem> | ||
121 | <listitem><para> | ||
122 | <link linkend='var-MULTI_PROVIDER_WHITELIST'><filename>MULTI_PROVIDER_WHITELIST</filename></link> | ||
123 | </para></listitem> | ||
124 | <listitem><para> | ||
125 | <link linkend='var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></link> | ||
126 | </para></listitem> | ||
127 | <listitem><para> | ||
128 | <filename>BBPKGS</filename> | ||
129 | </para></listitem> | ||
130 | <listitem><para> | ||
131 | <link linkend='var-BB_DEFAULT_TASK'><filename>BB_DEFAULT_TASK</filename></link> | ||
132 | </para></listitem> | ||
133 | <listitem><para> | ||
134 | <link linkend='var-TOPDIR'><filename>TOPDIR</filename></link> | ||
135 | </para></listitem> | ||
136 | <listitem><para> | ||
137 | <link linkend='var-BB_VERBOSE_LOGS'><filename>BB_VERBOSE_LOGS</filename></link> | ||
138 | </para></listitem> | ||
139 | <listitem><para> | ||
140 | <link linkend='var-BB_NICE_LEVEL'><filename>BB_NICE_LEVEL</filename></link> | ||
141 | </para></listitem> | ||
142 | <listitem><para> | ||
143 | <link linkend='var-BBFILE_COLLECTIONS'><filename>BBFILE_COLLECTIONS</filename></link> | ||
144 | </para></listitem> | ||
145 | <listitem><para> | ||
146 | <link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link> | ||
147 | </para></listitem> | ||
148 | <listitem><para> | ||
149 | <link linkend='var-BB_DANGLINGAPPENDS_WARNONLY'><filename>BB_DANGLINGAPPENDS_WARNONLY</filename></link> | ||
150 | </para></listitem> | ||
151 | <listitem><para> | ||
152 | <link linkend='var-BBINCLUDED'><filename>BBINCLUDED</filename></link> | ||
153 | </para></listitem> | ||
154 | <listitem><para> | ||
155 | <link linkend='var-BBFILE_PRIORITY'><filename>BBFILE_PRIORITY</filename></link> | ||
156 | </para></listitem> | ||
157 | <listitem><para> | ||
158 | <link linkend='var-BUILDNAME'><filename>BUILDNAME</filename></link> | ||
159 | </para></listitem> | ||
160 | <listitem><para> | ||
161 | <link linkend='var-BBMASK'><filename>BBMASK</filename></link> | ||
162 | </para></listitem> | ||
163 | </itemizedlist> | ||
164 | </para> | ||
165 | |||
166 | <para> | ||
167 | After parsing configuration files, BitBake uses its rudimentary | ||
168 | inheritance mechanism, which is through class files, to inherit | ||
169 | some standard classes. | ||
170 | BitBake parses a class when the inherit directive responsible | ||
171 | for getting that class is encountered. | ||
172 | </para> | ||
173 | |||
174 | <para> | ||
175 | The <filename>base.bbclass</filename> file is always included. | ||
176 | Other classes that are specified in the configuration using the | ||
177 | <link linkend='var-INHERIT'><filename>INHERIT</filename></link> | ||
178 | variable are also included. | ||
179 | BitBake searches for class files in a "classes" subdirectory under | ||
180 | the paths in <filename>BBPATH</filename> in the same way as | ||
181 | configuration files. | ||
182 | </para> | ||
183 | |||
184 | <para> | ||
185 | A good way to get an idea of the configuration files and | ||
186 | the class files used in your execution environment is to | ||
187 | run the following BitBake command: | ||
188 | <literallayout class='monospaced'> | ||
189 | $ bitbake -e > mybb.log | ||
190 | </literallayout> | ||
191 | Examining the top of the <filename>mybb.log</filename> | ||
192 | shows you the many configuration files and class files | ||
193 | used in your execution environment. | ||
194 | </para> | ||
195 | </section> | ||
196 | |||
197 | <section id='locating-recipes'> | ||
198 | <title>Locating Recipes</title> | ||
199 | |||
200 | <para> | ||
201 | The <filename>BBFILES</filename> variable is how BitBake | ||
202 | locates files. | ||
203 | This variable is a space-separated list of files | ||
204 | that are available, supports wildcards, and is set shortly | ||
205 | after the parsing phase of BitBake's execution. | ||
206 | </para> | ||
207 | |||
208 | <para> | ||
209 | <literallayout class='monospaced'> | ||
210 | BBFILES = "/path/to/bbfiles/*.bb" | ||
211 | </literallayout> | ||
212 | With regard to dependencies, it expects the | ||
213 | <filename>.bb</filename> to define a | ||
214 | <filename>DEPENDS</filename> variable, which contains a | ||
215 | space separated list of “package names”, which themselves | ||
216 | are the <filename>PN</filename> variable. The | ||
217 | <filename>PN</filename> variable is, in general, | ||
218 | set to a component of the <filename>.bb</filename> | ||
219 | filename by default. | ||
220 | </para> | ||
221 | </section> | ||
222 | |||
223 | <section id='parsing-recipes'> | ||
224 | <title>Parsing Recipes</title> | ||
225 | |||
226 | <para> | ||
227 | After classes are included, the variable | ||
228 | <filename>BBFILES</filename> is set, usually in | ||
229 | <filename>local.conf</filename>, and defines the list of | ||
230 | places to search for recipe and append files. | ||
231 | Adding extra content to <filename>BBFILES</filename> is best | ||
232 | achieved through the use of BitBake layers. | ||
233 | </para> | ||
234 | |||
235 | <para> | ||
236 | BitBake parses each recipe and append file located with | ||
237 | <filename>BBFILES</filename> and stores the values of various | ||
238 | variables into the datastore. | ||
239 | In summary, for each recipe and append file pairing, the configuration | ||
240 | plus the base class of variables are set, followed by the data in the | ||
241 | recipe file itself, followed by any inherit commands | ||
242 | that the recipe file might contain. | ||
243 | </para> | ||
244 | |||
245 | <para> | ||
246 | Part of parsing a recipe is making sure that all the recipes | ||
247 | that the recipe being parsed depends on are understood. | ||
248 | These other recipes could be located in other layers or in | ||
249 | a specific layer version. | ||
250 | These two variables in a recipe can help with with these | ||
251 | cases: | ||
252 | <itemizedlist> | ||
253 | <listitem><para> | ||
254 | <link linkend='var-LAYERDEPENDS'><filename>LAYERDEPENDS</filename></link> | ||
255 | </para></listitem> | ||
256 | <listitem><para> | ||
257 | <link linkend='var-LAYERVERSION'><filename>LAYERVERSION</filename></link> | ||
258 | </para></listitem> | ||
259 | </itemizedlist> | ||
260 | </para> | ||
261 | |||
262 | <para> | ||
263 | Because parsing recipe and append files is a time consuming | ||
264 | process, a cache, referred to as the "setscene" | ||
265 | is kept to speed up subsequent parsing. | ||
266 | The setscene is invalid if the timestamps of a recipe changes, | ||
267 | any of the include files change, configuration files change, | ||
268 | or class files on which the recipe file depends change. | ||
269 | </para> | ||
270 | </section> | ||
271 | |||
272 | <section id='executing-tasks'> | ||
273 | <title>Executing Tasks</title> | ||
274 | |||
275 | <para> | ||
276 | Tasks can either be a shell task or a Python task. | ||
277 | For shell tasks, BitBake writes a shell script to | ||
278 | <filename>${WORKDIR}/temp/run.do_taskname.pid</filename> | ||
279 | and then executes the script. | ||
280 | The generated shell script contains all the exported variables, | ||
281 | and the shell functions with all variables expanded. | ||
282 | Output from the shell script goes to the file | ||
283 | <filename>${WORKDIR}/temp/log.do_taskname.pid</filename>. | ||
284 | Looking at the expanded shell functions in the run file and | ||
285 | the output in the log files is a useful debugging technique. | ||
286 | </para> | ||
287 | |||
288 | <para> | ||
289 | For Python tasks, BitBake executes the task internally and logs | ||
290 | information to the controlling terminal. | ||
291 | Future versions of BitBake will write the functions to files | ||
292 | similar to the way shell tasks are handled. | ||
293 | Logging will be handled in a way similar to shell tasks as well. | ||
294 | </para> | ||
295 | |||
296 | <para> | ||
297 | Variables specific to scheduling functionality exist: | ||
298 | <itemizedlist> | ||
299 | <listitem><para> | ||
300 | <link linkend='var-BB_SCHEDULER'><filename>BB_SCHEDULER</filename></link> | ||
301 | </para></listitem> | ||
302 | <listitem><para> | ||
303 | <link linkend='var-BB_SCHEDULERS'><filename>BB_SCHEDULERS</filename></link> | ||
304 | </para></listitem> | ||
305 | </itemizedlist> | ||
306 | </para> | ||
307 | </section> | ||
308 | |||
309 | <section id='source-fetching-dev-environment'> | ||
310 | <title>Source Fetching</title> | ||
311 | |||
312 | <para> | ||
313 | The first stages of building a recipe are to fetch and unpack | ||
314 | the source code: | ||
315 | <imagedata fileref="figures/source-fetching.png" align="center" width="6.5in" depth="5in" /> | ||
316 | </para> | ||
317 | |||
318 | <para> | ||
319 | The <filename>do_fetch</filename> and | ||
320 | <filename>do_unpack</filename> tasks fetch the source files | ||
321 | and unpack them into the work directory. | ||
322 | By default, everything is accomplished in the | ||
323 | build directory, | ||
324 | which has a defined structure. | ||
325 | </para> | ||
326 | |||
327 | <para> | ||
328 | Unpacked source files are pointed to by a variable. | ||
329 | For example, in the Yocto Project and OpenEmbedded build systems, | ||
330 | the <filename>S</filename> variable points to these source files. | ||
331 | Each recipe has an area in the Build Directory where the | ||
332 | unpacked source code resides. | ||
333 | The name of that directory for any given recipe is defined from | ||
334 | several different variables. | ||
335 | You can see the variables that define these directories | ||
336 | by looking at the figure that shows the structure and variables | ||
337 | used in the Yocto Project: | ||
338 | <itemizedlist> | ||
339 | <listitem><para><filename>TMPDIR</filename> | ||
340 | </para></listitem> | ||
341 | <listitem><para><filename>PACKAGE_ARCH</filename> | ||
342 | </para></listitem> | ||
343 | <listitem><para><filename>TARGET_OS</filename> | ||
344 | </para></listitem> | ||
345 | <listitem><para><link linkend='var-PN'><filename>PN</filename></link> | ||
346 | </para></listitem> | ||
347 | <listitem><para><link linkend='var-PV'><filename>PV</filename></link> | ||
348 | </para></listitem> | ||
349 | <listitem><para><link linkend='var-PR'><filename>PR</filename></link> | ||
350 | </para></listitem> | ||
351 | <listitem><para><filename>WORKDIR</filename> | ||
352 | </para></listitem> | ||
353 | <listitem><para><filename>S</filename> | ||
354 | </para></listitem> | ||
355 | </itemizedlist> | ||
356 | </para> | ||
357 | |||
358 | <para> | ||
359 | Briefly, the <filename>S</filename> directory contains the | ||
360 | unpacked source files for a recipe. | ||
361 | The <filename>WORKDIR</filename> directory is where all the | ||
362 | building goes on for a given recipe. | ||
363 | </para> | ||
364 | </section> | ||
365 | |||
366 | <section id='patching-dev-environment'> | ||
367 | <title>Patching</title> | ||
368 | |||
369 | <para> | ||
370 | Once source code is fetched and unpacked, BitBake locates | ||
371 | patch files and applies them to the source files: | ||
372 | <imagedata fileref="figures/patching.png" align="center" width="6in" depth="5in" /> | ||
373 | </para> | ||
374 | |||
375 | <para> | ||
376 | The <filename>do_patch</filename> task processes recipes by | ||
377 | using the | ||
378 | <link linkend='var-SRC_URI'><filename>SRC_URI</filename></link> | ||
379 | variable to locate applicable patch files, which by default | ||
380 | are <filename>*.patch</filename> or | ||
381 | <filename>*.diff</filename> files, or any file if | ||
382 | "apply=yes" is specified for the file in | ||
383 | <filename>SRC_URI</filename>. | ||
384 | </para> | ||
31 | 385 | ||
32 | <section id='parsing-and-execution'> | 386 | <para> |
33 | <title>Parsing and Execution</title> | 387 | BitBake finds and applies multiple patches for a single recipe |
34 | 388 | in the order in which it finds the patches. | |
35 | <section id='parsing-overview'> | 389 | Patches are applied to the recipe's source files located in the |
36 | <title>Parsing Overview</title> | 390 | <filename>S</filename> directory. |
37 | 391 | </para> | |
38 | <para> | 392 | |
39 | BitBake parses configuration files, classes, recipes, and append | 393 | <para> |
40 | files. | 394 | For more information on how the source directories are |
41 | </para> | 395 | created, see the |
42 | 396 | "<link linkend='source-fetching-dev-environment'>Source Fetching</link>" | |
43 | <para> | 397 | section. |
44 | The first thing BitBake does is look for the | 398 | </para> |
45 | <filename>bitbake.conf</filename> file. | ||
46 | This file resides in the <filename>conf</filename> | ||
47 | directory, which must be listed in | ||
48 | <link linkend='var-BBPATH'><filename>BBPATH</filename></link>. | ||
49 | </para> | ||
50 | |||
51 | <para> | ||
52 | The <filename>bitbake.conf</filename> file lists other configuration | ||
53 | files to include from the <filename>conf</filename> directory below the | ||
54 | directories listed in <filename>BBPATH</filename>. | ||
55 | In general, the most important of these | ||
56 | configuration files from a user's perspective | ||
57 | is <filename>local.conf</filename>, which contains the user's | ||
58 | customized settings for the build environment. | ||
59 | </para> | ||
60 | |||
61 | <para> | ||
62 | Other notable configuration files are the distribution configuration | ||
63 | file and the machine configuration file. | ||
64 | These configuration files are normally identified by | ||
65 | variables unique to the build systems using BitBake. | ||
66 | For example, the Yocto Project uses the | ||
67 | <filename>DISTRO</filename> and <filename>MACHINE</filename> | ||
68 | variables, respectively. | ||
69 | </para> | ||
70 | |||
71 | <para> | ||
72 | After parsing of the configuration files, some standard classes are | ||
73 | included. | ||
74 | The <filename>base.bbclass</filename> file | ||
75 | is always included. | ||
76 | Other classes that are specified in the configuration using the | ||
77 | <link linkend='var-INHERIT'><filename>INHERIT</filename></link> | ||
78 | variable are also included. | ||
79 | BitBake searches for class files in a "classes" subdirectory under | ||
80 | the paths in <filename>BBPATH</filename> in the same way as | ||
81 | configuration files. | ||
82 | </para> | ||
83 | |||
84 | <para> | ||
85 | After classes are included, the variable | ||
86 | <filename>BBFILES</filename> is set, usually in | ||
87 | <filename>local.conf</filename>, and defines the list of | ||
88 | places to search for recipe and append files. | ||
89 | Adding extra content to <filename>BBFILES</filename> is best | ||
90 | achieved through the use of BitBake layers. | ||
91 | </para> | ||
92 | |||
93 | <para> | ||
94 | BitBake parses each recipe and append file located with | ||
95 | <filename>BBFILES</filename> and stores the values of various | ||
96 | variables into the datastore. | ||
97 | In summary, for each recipe and append file pairing, the configuration | ||
98 | plus the base class of variables are set, followed by the data in the | ||
99 | recipe file itself, followed by any inherit commands | ||
100 | that the recipe file might contain. | ||
101 | </para> | ||
102 | |||
103 | <para> | ||
104 | Because parsing recipe and append files is a time consuming | ||
105 | process, a cache, referred to as the "setscene" | ||
106 | is kept to speed up subsequent parsing. | ||
107 | The setscene is invalid if the timestamps of a recipe changes, | ||
108 | any of the include files change, configuration files change, | ||
109 | or class files on which the recipe file depends change. | ||
110 | </para> | ||
111 | </section> | ||
112 | |||
113 | <section id='parsing-configuration-files'> | ||
114 | <title>Configuration files</title> | ||
115 | |||
116 | <para> | ||
117 | Prior to parsing configuration files, Bitbake looks | ||
118 | at certain variables, including: | ||
119 | <itemizedlist> | ||
120 | <listitem><para><link linkend='var-BB_ENV_WHITELIST'><filename>BB_ENV_WHITELIST</filename></link></para></listitem> | ||
121 | <listitem><para><link linkend='var-BB_PRESERVE_ENV'><filename>BB_PRESERVE_ENV</filename></link></para></listitem> | ||
122 | <listitem><para><link linkend='var-BB_ENV_EXTRAWHITE'><filename>BB_ENV_EXTRAWHITE</filename></link></para></listitem> | ||
123 | <listitem><para><link linkend='var-BB_ORIGENV'><filename>BB_ORIGENV</filename></link></para></listitem> | ||
124 | <listitem><para><link linkend='var-PREFERRED_VERSION'><filename>PREFERRED_VERSION</filename></link></para></listitem> | ||
125 | <listitem><para><link linkend='var-PREFERRED_PROVIDERS'><filename>PREFERRED_PROVIDERS</filename></link></para></listitem> | ||
126 | </itemizedlist> | ||
127 | </para> | ||
128 | |||
129 | <para> | ||
130 | The first kind of metadata in BitBake is configuration metadata. | ||
131 | This metadata is global, and therefore affects all packages and | ||
132 | tasks that are executed. | ||
133 | </para> | ||
134 | |||
135 | <para> | ||
136 | BitBake will first search the current working directory for an | ||
137 | optional <filename>conf/bblayers.conf</filename> configuration file. | ||
138 | This file is expected to contain a | ||
139 | <link linkend='var-BBLAYERS'><filename>BBLAYERS</filename></link> | ||
140 | variable that is a space delimited list of 'layer' directories. | ||
141 | For each directory in this list, a <filename>conf/layer.conf</filename> | ||
142 | file will be searched for and parsed with the | ||
143 | <link linkend='var-LAYERDIR'><filename>LAYERDIR</filename></link> | ||
144 | variable being set to the directory where the layer was found. | ||
145 | The idea is these files will setup | ||
146 | <link linkend='var-BBPATH'><filename>BBPATH</filename></link> | ||
147 | and other variables correctly for a given build directory automatically | ||
148 | for the user. | ||
149 | </para> | ||
150 | |||
151 | <para> | ||
152 | BitBake will then expect to find <filename>conf/bitbake.conf</filename> | ||
153 | file somewhere in the user specified <filename>BBPATH</filename>. | ||
154 | That configuration file generally has include directives to pull | ||
155 | in any other metadata (generally files specific to architecture, | ||
156 | machine, local and so on). | ||
157 | </para> | ||
158 | |||
159 | <para> | ||
160 | Only variable definitions and include directives are allowed | ||
161 | in <filename>.conf</filename> files. | ||
162 | The following variables include: | ||
163 | <itemizedlist> | ||
164 | <listitem><para> | ||
165 | <link linkend='var-BITBAKE_UI'><filename>BITBAKE_UI</filename></link> | ||
166 | </para></listitem> | ||
167 | <listitem><para> | ||
168 | <link linkend='var-BBDEBUG'><filename>BBDEBUG</filename></link> | ||
169 | </para></listitem> | ||
170 | <listitem><para> | ||
171 | <link linkend='var-MULTI_PROVIDER_WHITELIST'><filename>MULTI_PROVIDER_WHITELIST</filename></link> | ||
172 | </para></listitem> | ||
173 | <listitem><para> | ||
174 | <link linkend='var-BB_NUMBER_PARSE_THREADS'><filename>BB_NUMBER_PARSE_THREADS</filename></link> | ||
175 | </para></listitem> | ||
176 | <listitem><para> | ||
177 | <filename>BBPKGS</filename> | ||
178 | </para></listitem> | ||
179 | <listitem><para> | ||
180 | <link linkend='var-BB_DEFAULT_TASK'><filename>BB_DEFAULT_TASK</filename></link> | ||
181 | </para></listitem> | ||
182 | <listitem><para> | ||
183 | <link linkend='var-TOPDIR'><filename>TOPDIR</filename></link> | ||
184 | </para></listitem> | ||
185 | <listitem><para> | ||
186 | <link linkend='var-BB_VERBOSE_LOGS'><filename>BB_VERBOSE_LOGS</filename></link> | ||
187 | </para></listitem> | ||
188 | <listitem><para> | ||
189 | <link linkend='var-BB_NICE_LEVEL'><filename>BB_NICE_LEVEL</filename></link> | ||
190 | </para></listitem> | ||
191 | <listitem><para> | ||
192 | <link linkend='var-BBFILE_COLLECTIONS'><filename>BBFILE_COLLECTIONS</filename></link> | ||
193 | </para></listitem> | ||
194 | <listitem><para> | ||
195 | <link linkend='var-ASSUME_PROVIDED'><filename>ASSUME_PROVIDED</filename></link> | ||
196 | </para></listitem> | ||
197 | <listitem><para> | ||
198 | <link linkend='var-BB_DANGLINGAPPENDS_WARNONLY'><filename>BB_DANGLINGAPPENDS_WARNONLY</filename></link> | ||
199 | </para></listitem> | ||
200 | <listitem><para> | ||
201 | <link linkend='var-BBINCLUDED'><filename>BBINCLUDED</filename></link> | ||
202 | </para></listitem> | ||
203 | <listitem><para> | ||
204 | <link linkend='var-BBFILE_PRIORITY'><filename>BBFILE_PRIORITY</filename></link> | ||
205 | </para></listitem> | ||
206 | <listitem><para> | ||
207 | <link linkend='var-BUILDNAME'><filename>BUILDNAME</filename></link> | ||
208 | </para></listitem> | ||
209 | <listitem><para> | ||
210 | <link linkend='var-BBMASK'><filename>BBMASK</filename></link> | ||
211 | </para></listitem> | ||
212 | </itemizedlist> | ||
213 | </para> | ||
214 | |||
215 | <section id='layers'> | ||
216 | <title>Layers</title> | ||
217 | |||
218 | <para> | ||
219 | Layers allow you to isolate different types of | ||
220 | customizations from each other. | ||
221 | While you might find it tempting to keep everything in one layer | ||
222 | when working on a single project, the more modular you organize | ||
223 | your metadata, the easier it is to cope with future changes. | ||
224 | </para> | ||
225 | |||
226 | <para> | ||
227 | To illustrate how you can use layers to keep things modular, | ||
228 | consider machine customizations. | ||
229 | These types of customizations typically reside in a special layer, | ||
230 | rather than a general layer, called a Board Specific Package (BSP) Layer. | ||
231 | Furthermore, the machine customizations should be isolated from | ||
232 | recipes and metadata that support a new GUI environment, for | ||
233 | example. | ||
234 | This situation gives you a couple of layers: one for the machine | ||
235 | configurations and one for the GUI environment. | ||
236 | It is important to understand, however, that the BSP layer can still | ||
237 | make machine-specific additions to recipes within | ||
238 | the GUI environment layer without polluting the GUI layer itself | ||
239 | with those machine-specific changes. | ||
240 | You can accomplish this through a recipe that is a BitBake append | ||
241 | (<filename>.bbappend</filename>) file. | ||
242 | </para> | ||
243 | |||
244 | <para> | ||
245 | There are certain variables specific to layers: | ||
246 | <itemizedlist> | ||
247 | <listitem><para> | ||
248 | <link linkend='var-LAYERDEPENDS'><filename>LAYERDEPENDS</filename></link> | ||
249 | </para></listitem> | ||
250 | <listitem><para> | ||
251 | <link linkend='var-LAYERVERSION'><filename>LAYERVERSION</filename></link> | ||
252 | </para></listitem> | ||
253 | </itemizedlist> | ||
254 | </para> | ||
255 | </section> | ||
256 | |||
257 | <section id='schedulers'> | ||
258 | <title>Schedulers</title> | ||
259 | |||
260 | <para> | ||
261 | Variables specific to scheduling functionality exist: | ||
262 | <itemizedlist> | ||
263 | <listitem><para> | ||
264 | <link linkend='var-BB_SCHEDULER'><filename>BB_SCHEDULER</filename></link> | ||
265 | </para></listitem> | ||
266 | <listitem><para> | ||
267 | <link linkend='var-BB_SCHEDULERS'><filename>BB_SCHEDULERS</filename></link> | ||
268 | </para></listitem> | ||
269 | </itemizedlist> | ||
270 | </para> | ||
271 | </section> | ||
272 | </section> | ||
273 | |||
274 | <section id='metadata-classes'> | ||
275 | <title>Classes</title> | ||
276 | |||
277 | <para> | ||
278 | BitBake's rudimentary inheritance mechanism is accomplished using | ||
279 | classes. | ||
280 | As briefly mentioned in the metadata introduction, BitBake | ||
281 | parses a class when an inherit directive is encountered, and it | ||
282 | is located in the <filename>classes</filename> directory | ||
283 | relative to the directories in | ||
284 | <link linkend='var-BBPATH'><filename>BBPATH</filename></link>. | ||
285 | </para> | ||
286 | </section> | ||
287 | |||
288 | <section id='recipe-bb-files'> | ||
289 | <title>Recipe (<filename>.bb</filename>) Files</title> | ||
290 | |||
291 | <para> | ||
292 | Recipe files, which are files that have the | ||
293 | <filename>.bb</filename> file extension, are logical units of | ||
294 | tasks for execution. | ||
295 | Normally, that logical unit is a package that needs to be | ||
296 | built. | ||
297 | </para> | ||
298 | |||
299 | <para> | ||
300 | BitBake obeys all inter-recipe dependencies. | ||
301 | </para> | ||
302 | |||
303 | <para> | ||
304 | Recipe files must reside in locations found in the | ||
305 | <link linkend='var-BBFILES'><filename>BBFILES</filename></link> | ||
306 | variable. | ||
307 | </para> | ||
308 | </section> | ||
309 | |||
310 | <section id='append-bbappend-files'> | ||
311 | <title>Append (<filename>.bbappend</filename>) Files</title> | ||
312 | |||
313 | <para> | ||
314 | Append files, which are files that have the | ||
315 | <filename>.bbappend</filename> file extension, add or | ||
316 | extend build information to an existing | ||
317 | <link linkend='recipe-bb-files'>recipe file</link>. | ||
318 | </para> | ||
319 | |||
320 | <para> | ||
321 | BitBake expects every append file to have a corresponding recipe file. | ||
322 | Furthermore, the append file and corresponding recipe file | ||
323 | must use the same root filename. | ||
324 | The filenames can differ only in the file type suffix used | ||
325 | (e.g. <filename>formfactor_0.0.bb</filename> and | ||
326 | <filename>formfactor_0.0.bbappend</filename>). | ||
327 | </para> | ||
328 | |||
329 | <para> | ||
330 | Information in append files overrides the information in the | ||
331 | similarly-named recipe file. | ||
332 | </para> | ||
333 | </section> | ||
334 | </section> | 399 | </section> |
335 | 400 | ||
336 | <section id='bitbake-dev-environment'> | 401 | <section id='configuration-and-compilation-dev-environment'> |
337 | <title>BitBake</title> | 402 | <title>Configuration and Compilation</title> |
338 | |||
339 | <para> | ||
340 | The OpenEmbedded build system uses BitBake to produce images. | ||
341 | BitBake consists of several functional areas. | ||
342 | This section takes a closer look at each of those areas. | ||
343 | </para> | ||
344 | |||
345 | <section id='source-fetching-dev-environment'> | ||
346 | <title>Source Fetching</title> | ||
347 | |||
348 | <para> | ||
349 | The first stages of building a recipe are to fetch and unpack | ||
350 | the source code: | ||
351 | <imagedata fileref="figures/source-fetching.png" align="center" width="6.5in" depth="5in" /> | ||
352 | </para> | ||
353 | figures/ | ||
354 | <para> | ||
355 | The <filename>do_fetch</filename> and | ||
356 | <filename>do_unpack</filename> tasks fetch the source files | ||
357 | and unpack them into the work directory. | ||
358 | By default, everything is accomplished in the | ||
359 | build directory, | ||
360 | which has a defined structure. | ||
361 | </para> | ||
362 | |||
363 | <para> | ||
364 | Unpacked source files are pointed to by a variable. | ||
365 | For example, in the Yocto Project and OpenEmbedded build systems, | ||
366 | the <filename>S</filename> variable points to these source files. | ||
367 | Each recipe has an area in the Build Directory where the | ||
368 | unpacked source code resides. | ||
369 | The name of that directory for any given recipe is defined from | ||
370 | several different variables. | ||
371 | You can see the variables that define these directories | ||
372 | by looking at the figure that shows the structure and variables | ||
373 | used in the Yocto Project: | ||
374 | <itemizedlist> | ||
375 | <listitem><para><filename>TMPDIR</filename> | ||
376 | </para></listitem> | ||
377 | <listitem><para><filename>PACKAGE_ARCH</filename> | ||
378 | </para></listitem> | ||
379 | <listitem><para><filename>TARGET_OS</filename> | ||
380 | </para></listitem> | ||
381 | <listitem><para><link linkend='var-PN'><filename>PN</filename></link> | ||
382 | </para></listitem> | ||
383 | <listitem><para><link linkend='var-PV'><filename>PV</filename></link> | ||
384 | </para></listitem> | ||
385 | <listitem><para><link linkend='var-PR'><filename>PR</filename></link> | ||
386 | </para></listitem> | ||
387 | <listitem><para><filename>WORKDIR</filename> | ||
388 | </para></listitem> | ||
389 | <listitem><para><filename>S</filename> | ||
390 | </para></listitem> | ||
391 | </itemizedlist> | ||
392 | </para> | ||
393 | |||
394 | <para> | ||
395 | Briefly, the <filename>S</filename> directory contains the | ||
396 | unpacked source files for a recipe. | ||
397 | The <filename>WORKDIR</filename> directory is where all the | ||
398 | building goes on for a given recipe. | ||
399 | </para> | ||
400 | </section> | ||
401 | |||
402 | <section id='patching-dev-environment'> | ||
403 | <title>Patching</title> | ||
404 | |||
405 | <para> | ||
406 | Once source code is fetched and unpacked, BitBake locates | ||
407 | patch files and applies them to the source files: | ||
408 | <imagedata fileref="figures/patching.png" align="center" width="6in" depth="5in" /> | ||
409 | </para> | ||
410 | |||
411 | <para> | ||
412 | The <filename>do_patch</filename> task processes recipes by | ||
413 | using the | ||
414 | <link linkend='var-SRC_URI'><filename>SRC_URI</filename></link> | ||
415 | variable to locate applicable patch files, which by default | ||
416 | are <filename>*.patch</filename> or | ||
417 | <filename>*.diff</filename> files, or any file if | ||
418 | "apply=yes" is specified for the file in | ||
419 | <filename>SRC_URI</filename>. | ||
420 | </para> | ||
421 | |||
422 | <para> | ||
423 | BitBake finds and applies multiple patches for a single recipe | ||
424 | in the order in which it finds the patches. | ||
425 | Patches are applied to the recipe's source files located in the | ||
426 | <filename>S</filename> directory. | ||
427 | </para> | ||
428 | |||
429 | <para> | ||
430 | For more information on how the source directories are | ||
431 | created, see the | ||
432 | "<link linkend='source-fetching-dev-environment'>Source Fetching</link>" | ||
433 | section. | ||
434 | </para> | ||
435 | </section> | ||
436 | |||
437 | <section id='configuration-and-compilation-dev-environment'> | ||
438 | <title>Configuration and Compilation</title> | ||
439 | |||
440 | <para> | ||
441 | After source code is patched, BitBake executes tasks that | ||
442 | configure and compile the source code: | ||
443 | <imagedata fileref="figures/configuration-compile-autoreconf.png" align="center" width="7in" depth="5in" /> | ||
444 | </para> | ||
445 | |||
446 | <para> | ||
447 | This step in the build process consists of three tasks: | ||
448 | <itemizedlist> | ||
449 | <listitem><para><emphasis><filename>do_configure</filename>:</emphasis> | ||
450 | This task configures the source by enabling and | ||
451 | disabling any build-time and configuration options for | ||
452 | the software being built. | ||
453 | Configurations can come from the recipe itself as well | ||
454 | as from an inherited class. | ||
455 | Additionally, the software itself might configure itself | ||
456 | depending on the target for which it is being built. | ||
457 | </para> | ||
458 | |||
459 | <para>The configurations handled by the | ||
460 | <filename>do_configure</filename> task are specific | ||
461 | to source code configuration for the source code | ||
462 | being built by the recipe.</para> | ||
463 | |||
464 | <para>If you are using the Autotools class | ||
465 | (<filename>autotools.bbclass</filename>), | ||
466 | you can add additional configuration options by using | ||
467 | the <filename>EXTRA_OECONF</filename> | ||
468 | variable. | ||
469 | For information on how this variable works within | ||
470 | that class, see the | ||
471 | <filename>meta/classes/autotools.bbclass</filename> file. | ||
472 | </para></listitem> | ||
473 | <listitem><para><emphasis><filename>do_compile</filename>:</emphasis> | ||
474 | Once a configuration task has been satisfied, BitBake | ||
475 | compiles the source using the | ||
476 | <filename>do_compile</filename> task. | ||
477 | Compilation occurs in the directory pointed to by the | ||
478 | <link linkend='var-B'><filename>B</filename></link> | ||
479 | variable. | ||
480 | Realize that the <filename>B</filename> directory is, by | ||
481 | default, the same as the | ||
482 | <filename>S</filename> | ||
483 | directory.</para></listitem> | ||
484 | <listitem><para><emphasis><filename>do_install</filename>:</emphasis> | ||
485 | Once compilation is done, BitBake executes the | ||
486 | <filename>do_install</filename> task. | ||
487 | This task copies files from the <filename>B</filename> | ||
488 | directory and places them in a holding area pointed to | ||
489 | by the <filename>D</filename> variable.</para></listitem> | ||
490 | </itemizedlist> | ||
491 | </para> | ||
492 | </section> | ||
493 | |||
494 | <section id='package-splitting-dev-environment'> | ||
495 | <title>Package Splitting</title> | ||
496 | |||
497 | <para> | ||
498 | After source code is configured and compiled, the | ||
499 | OpenEmbedded build system analyzes | ||
500 | the results and splits the output into packages: | ||
501 | <imagedata fileref="figures/analysis-for-package-splitting.png" align="center" width="7in" depth="7in" /> | ||
502 | </para> | ||
503 | |||
504 | <para> | ||
505 | The <filename>do_package</filename> and | ||
506 | <filename>do_packagedata</filename> tasks combine to analyze | ||
507 | the files found in the <filename>D</filename> directory | ||
508 | and split them into subsets based on available packages and | ||
509 | files. | ||
510 | The analyzing process involves the following as well as other | ||
511 | items: splitting out debugging symbols, | ||
512 | looking at shared library dependencies between packages, | ||
513 | and looking at package relationships. | ||
514 | The <filename>do_packagedata</filename> task creates package | ||
515 | metadata based on the analysis such that the | ||
516 | OpenEmbedded build system can generate the final packages. | ||
517 | Working, staged, and intermediate results of the analysis | ||
518 | and package splitting process use these areas: | ||
519 | <itemizedlist> | ||
520 | <listitem><para><filename>PKGD</filename> | ||
521 | </para></listitem> | ||
522 | <listitem><para><filename>PKGDATA_DIR</filename> | ||
523 | </para></listitem> | ||
524 | <listitem><para><filename>PKGDESTWORK</filename> | ||
525 | </para></listitem> | ||
526 | <listitem><para><filename>PKGDEST</filename> | ||
527 | </para></listitem> | ||
528 | </itemizedlist> | ||
529 | The <filename>FILES</filename> | ||
530 | variable defines the files that go into each package in | ||
531 | <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>. | ||
532 | If you want details on how this is accomplished in the Yocto Project | ||
533 | for example, you can look at the <filename>package.bbclass</filename> | ||
534 | file in a Yocto tree. | ||
535 | </para> | ||
536 | |||
537 | <para> | ||
538 | Depending on the type of packages being created (RPM, DEB, or | ||
539 | IPK), the <filename>do_package_write_*</filename> task | ||
540 | creates the actual packages and places them in the | ||
541 | Package Feed area, which is | ||
542 | <filename>${TMPDIR}/deploy</filename>. | ||
543 | <note> | ||
544 | Support for creating feeds directly from the | ||
545 | <filename>deploy/*</filename> directories does not exist. | ||
546 | Creating such feeds usually requires some kind of feed | ||
547 | maintenance mechanism that would upload the new packages | ||
548 | into an official package feed (e.g. the | ||
549 | Ångström distribution). | ||
550 | This functionality is highly distribution-specific | ||
551 | and thus is not provided out of the box. | ||
552 | </note> | ||
553 | </para> | ||
554 | </section> | ||
555 | |||
556 | <section id='image-generation-dev-environment'> | ||
557 | <title>Image Generation</title> | ||
558 | |||
559 | <para> | ||
560 | Once packages are split and stored in the Package Feeds area, | ||
561 | the OpenEmbedded build system uses BitBake to generate the | ||
562 | root filesystem image: | ||
563 | <imagedata fileref="figures/image-generation.png" align="center" width="6in" depth="7in" /> | ||
564 | </para> | ||
565 | |||
566 | <para> | ||
567 | The image generation process consists of several stages and | ||
568 | depends on many variables. | ||
569 | The <filename>do_rootfs</filename> task uses these key variables | ||
570 | to help create the list of packages to actually install: | ||
571 | <itemizedlist> | ||
572 | <listitem><para><filename>IMAGE_INSTALL</filename>: | ||
573 | Lists out the base set of packages to install from | ||
574 | the Package Feeds area.</para></listitem> | ||
575 | <listitem><para><filename>PACKAGE_EXCLUDE</filename>: | ||
576 | Specifies packages that should not be installed. | ||
577 | </para></listitem> | ||
578 | <listitem><para><filename>IMAGE_FEATURES</filename>: | ||
579 | Specifies features to include in the image. | ||
580 | Most of these features map to additional packages for | ||
581 | installation.</para></listitem> | ||
582 | <listitem><para><filename>PACKAGE_CLASSES</filename>: | ||
583 | Specifies the package backend to use and consequently | ||
584 | helps determine where to locate packages within the | ||
585 | Package Feeds area.</para></listitem> | ||
586 | <listitem><para><filename>IMAGE_LINGUAS</filename>: | ||
587 | Determines the language(s) for which additional | ||
588 | language support packages are installed. | ||
589 | </para></listitem> | ||
590 | </itemizedlist> | ||
591 | </para> | ||
592 | |||
593 | <para> | ||
594 | Package installation is under control of the package manager | ||
595 | (e.g. smart/rpm, opkg, or apt/dpkg) regardless of whether or | ||
596 | not package management is enabled for the target. | ||
597 | At the end of the process, if package management is not | ||
598 | enabled for the target, the package manager's data files | ||
599 | are deleted from the root filesystem. | ||
600 | </para> | ||
601 | |||
602 | <para> | ||
603 | During image generation, the build system attempts to run | ||
604 | all post-installation scripts. | ||
605 | Any that fail to run on the build host are run on the | ||
606 | target when the target system is first booted. | ||
607 | If you are using a | ||
608 | read-only root filesystem, | ||
609 | all the post installation scripts must succeed during the | ||
610 | package installation phase since the root filesystem cannot be | ||
611 | written into. | ||
612 | </para> | ||
613 | |||
614 | <para> | ||
615 | During Optimization, optimizing processes are run across | ||
616 | the image. | ||
617 | These processes include <filename>mklibs</filename> and | ||
618 | <filename>prelink</filename>. | ||
619 | The <filename>mklibs</filename> process optimizes the size | ||
620 | of the libraries. | ||
621 | A <filename>prelink</filename> process optimizes the dynamic | ||
622 | linking of shared libraries to reduce start up time of | ||
623 | executables. | ||
624 | </para> | ||
625 | |||
626 | <para> | ||
627 | Part of the image generation process includes compressing the | ||
628 | root filesystem image. | ||
629 | Compression is accomplished through several optimization | ||
630 | routines designed to reduce the overall size of the image. | ||
631 | </para> | ||
632 | |||
633 | <para> | ||
634 | After the root filesystem has been constructed, the image | ||
635 | generation process turns everything into an image file or | ||
636 | a set of image files. | ||
637 | The formats used for the root filesystem depend on the | ||
638 | <filename>IMAGE_FSTYPES</filename> variable. | ||
639 | </para> | ||
640 | 403 | ||
404 | <para> | ||
405 | After source code is patched, BitBake executes tasks that | ||
406 | configure and compile the source code: | ||
407 | <imagedata fileref="figures/configuration-compile-autoreconf.png" align="center" width="7in" depth="5in" /> | ||
408 | </para> | ||
409 | |||
410 | <para> | ||
411 | This step in the build process consists of three tasks: | ||
412 | <itemizedlist> | ||
413 | <listitem><para><emphasis><filename>do_configure</filename>:</emphasis> | ||
414 | This task configures the source by enabling and | ||
415 | disabling any build-time and configuration options for | ||
416 | the software being built. | ||
417 | Configurations can come from the recipe itself as well | ||
418 | as from an inherited class. | ||
419 | Additionally, the software itself might configure itself | ||
420 | depending on the target for which it is being built. | ||
421 | </para> | ||
422 | |||
423 | <para>The configurations handled by the | ||
424 | <filename>do_configure</filename> task are specific | ||
425 | to source code configuration for the source code | ||
426 | being built by the recipe.</para> | ||
427 | |||
428 | <para>If you are using the Autotools class | ||
429 | (<filename>autotools.bbclass</filename>), | ||
430 | you can add additional configuration options by using | ||
431 | the <filename>EXTRA_OECONF</filename> | ||
432 | variable. | ||
433 | For information on how this variable works within | ||
434 | that class, see the | ||
435 | <filename>meta/classes/autotools.bbclass</filename> file. | ||
436 | </para></listitem> | ||
437 | <listitem><para><emphasis><filename>do_compile</filename>:</emphasis> | ||
438 | Once a configuration task has been satisfied, BitBake | ||
439 | compiles the source using the | ||
440 | <filename>do_compile</filename> task. | ||
441 | Compilation occurs in the directory pointed to by the | ||
442 | <link linkend='var-B'><filename>B</filename></link> | ||
443 | variable. | ||
444 | Realize that the <filename>B</filename> directory is, by | ||
445 | default, the same as the | ||
446 | <filename>S</filename> | ||
447 | directory.</para></listitem> | ||
448 | <listitem><para><emphasis><filename>do_install</filename>:</emphasis> | ||
449 | Once compilation is done, BitBake executes the | ||
450 | <filename>do_install</filename> task. | ||
451 | This task copies files from the <filename>B</filename> | ||
452 | directory and places them in a holding area pointed to | ||
453 | by the <filename>D</filename> variable.</para></listitem> | ||
454 | </itemizedlist> | ||
455 | </para> | ||
456 | </section> | ||
457 | |||
458 | <section id='package-splitting-dev-environment'> | ||
459 | <title>Package Splitting</title> | ||
460 | |||
461 | <para> | ||
462 | After source code is configured and compiled, the | ||
463 | OpenEmbedded build system analyzes | ||
464 | the results and splits the output into packages: | ||
465 | <imagedata fileref="figures/analysis-for-package-splitting.png" align="center" width="7in" depth="7in" /> | ||
466 | </para> | ||
467 | |||
468 | <para> | ||
469 | The <filename>do_package</filename> and | ||
470 | <filename>do_packagedata</filename> tasks combine to analyze | ||
471 | the files found in the <filename>D</filename> directory | ||
472 | and split them into subsets based on available packages and | ||
473 | files. | ||
474 | The analyzing process involves the following as well as other | ||
475 | items: splitting out debugging symbols, | ||
476 | looking at shared library dependencies between packages, | ||
477 | and looking at package relationships. | ||
478 | The <filename>do_packagedata</filename> task creates package | ||
479 | metadata based on the analysis such that the | ||
480 | OpenEmbedded build system can generate the final packages. | ||
481 | Working, staged, and intermediate results of the analysis | ||
482 | and package splitting process use these areas: | ||
483 | <itemizedlist> | ||
484 | <listitem><para><filename>PKGD</filename> | ||
485 | </para></listitem> | ||
486 | <listitem><para><filename>PKGDATA_DIR</filename> | ||
487 | </para></listitem> | ||
488 | <listitem><para><filename>PKGDESTWORK</filename> | ||
489 | </para></listitem> | ||
490 | <listitem><para><filename>PKGDEST</filename> | ||
491 | </para></listitem> | ||
492 | </itemizedlist> | ||
493 | The <filename>FILES</filename> | ||
494 | variable defines the files that go into each package in | ||
495 | <link linkend='var-PACKAGES'><filename>PACKAGES</filename></link>. | ||
496 | If you want details on how this is accomplished in the Yocto Project | ||
497 | for example, you can look at the <filename>package.bbclass</filename> | ||
498 | file in a Yocto tree. | ||
499 | </para> | ||
500 | |||
501 | <para> | ||
502 | Depending on the type of packages being created (RPM, DEB, or | ||
503 | IPK), the <filename>do_package_write_*</filename> task | ||
504 | creates the actual packages and places them in the | ||
505 | Package Feed area, which is | ||
506 | <filename>${TMPDIR}/deploy</filename>. | ||
641 | <note> | 507 | <note> |
642 | The entire image generation process is run under Pseudo. | 508 | Support for creating feeds directly from the |
643 | Running under Pseudo ensures that the files in the root | 509 | <filename>deploy/*</filename> directories does not exist. |
644 | filesystem have correct ownership. | 510 | Creating such feeds usually requires some kind of feed |
511 | maintenance mechanism that would upload the new packages | ||
512 | into an official package feed (e.g. the | ||
513 | Ångström distribution). | ||
514 | This functionality is highly distribution-specific | ||
515 | and thus is not provided out of the box. | ||
645 | </note> | 516 | </note> |
646 | </section> | 517 | </para> |
647 | 518 | </section> | |
648 | <section id='sdk-generation-dev-environment'> | 519 | |
649 | <title>SDK Generation</title> | 520 | <section id='image-generation-dev-environment'> |
650 | 521 | <title>Image Generation</title> | |
651 | <para> | 522 | |
652 | The OpenEmbedded build system uses BitBake to generate the | 523 | <para> |
653 | Software Development Kit (SDK) installer script: | 524 | Once packages are split and stored in the Package Feeds area, |
654 | <imagedata fileref="figures/sdk-generation.png" align="center" width="6in" depth="7in" /> | 525 | the OpenEmbedded build system uses BitBake to generate the |
655 | </para> | 526 | root filesystem image: |
656 | 527 | <imagedata fileref="figures/image-generation.png" align="center" width="6in" depth="7in" /> | |
657 | <para> | 528 | </para> |
658 | Like image generation, the SDK script process consists of | 529 | |
659 | several stages and depends on many variables. | 530 | <para> |
660 | The <filename>do_populate_sdk</filename> task uses these | 531 | The image generation process consists of several stages and |
661 | key variables to help create the list of packages to actually | 532 | depends on many variables. |
662 | install. | 533 | The <filename>do_rootfs</filename> task uses these key variables |
663 | </para> | 534 | to help create the list of packages to actually install: |
664 | 535 | <itemizedlist> | |
665 | <para> | 536 | <listitem><para><filename>IMAGE_INSTALL</filename>: |
666 | The <filename>do_populate_sdk</filename> task handles two | 537 | Lists out the base set of packages to install from |
667 | parts: a target part and a host part. | 538 | the Package Feeds area.</para></listitem> |
668 | The target part is the part built for the target hardware and | 539 | <listitem><para><filename>PACKAGE_EXCLUDE</filename>: |
669 | includes libraries and headers. | 540 | Specifies packages that should not be installed. |
670 | The host part is the part of the SDK that runs on the | 541 | </para></listitem> |
671 | <filename>SDKMACHINE</filename>. | 542 | <listitem><para><filename>IMAGE_FEATURES</filename>: |
672 | </para> | 543 | Specifies features to include in the image. |
673 | 544 | Most of these features map to additional packages for | |
674 | <para> | 545 | installation.</para></listitem> |
675 | Once both parts are constructed, the | 546 | <listitem><para><filename>PACKAGE_CLASSES</filename>: |
676 | <filename>do_populate_sdk</filename> task performs some cleanup | 547 | Specifies the package backend to use and consequently |
677 | on both parts. | 548 | helps determine where to locate packages within the |
678 | After the cleanup, the task creates a cross-development | 549 | Package Feeds area.</para></listitem> |
679 | environment setup script and any configuration files that | 550 | <listitem><para><filename>IMAGE_LINGUAS</filename>: |
680 | might be needed. | 551 | Determines the language(s) for which additional |
681 | </para> | 552 | language support packages are installed. |
682 | 553 | </para></listitem> | |
683 | <para> | 554 | </itemizedlist> |
684 | The final output of the task is the Cross-development | 555 | </para> |
685 | toolchain installation script (<filename>.sh</filename> file), | 556 | |
686 | which includes the environment setup script. | 557 | <para> |
687 | </para> | 558 | Package installation is under control of the package manager |
688 | </section> | 559 | (e.g. smart/rpm, opkg, or apt/dpkg) regardless of whether or |
560 | not package management is enabled for the target. | ||
561 | At the end of the process, if package management is not | ||
562 | enabled for the target, the package manager's data files | ||
563 | are deleted from the root filesystem. | ||
564 | </para> | ||
565 | |||
566 | <para> | ||
567 | During image generation, the build system attempts to run | ||
568 | all post-installation scripts. | ||
569 | Any that fail to run on the build host are run on the | ||
570 | target when the target system is first booted. | ||
571 | If you are using a | ||
572 | read-only root filesystem, | ||
573 | all the post installation scripts must succeed during the | ||
574 | package installation phase since the root filesystem cannot be | ||
575 | written into. | ||
576 | </para> | ||
577 | |||
578 | <para> | ||
579 | During Optimization, optimizing processes are run across | ||
580 | the image. | ||
581 | These processes include <filename>mklibs</filename> and | ||
582 | <filename>prelink</filename>. | ||
583 | The <filename>mklibs</filename> process optimizes the size | ||
584 | of the libraries. | ||
585 | A <filename>prelink</filename> process optimizes the dynamic | ||
586 | linking of shared libraries to reduce start up time of | ||
587 | executables. | ||
588 | </para> | ||
589 | |||
590 | <para> | ||
591 | Part of the image generation process includes compressing the | ||
592 | root filesystem image. | ||
593 | Compression is accomplished through several optimization | ||
594 | routines designed to reduce the overall size of the image. | ||
595 | </para> | ||
596 | |||
597 | <para> | ||
598 | After the root filesystem has been constructed, the image | ||
599 | generation process turns everything into an image file or | ||
600 | a set of image files. | ||
601 | The formats used for the root filesystem depend on the | ||
602 | <filename>IMAGE_FSTYPES</filename> variable. | ||
603 | </para> | ||
604 | |||
605 | <note> | ||
606 | The entire image generation process is run under Pseudo. | ||
607 | Running under Pseudo ensures that the files in the root | ||
608 | filesystem have correct ownership. | ||
609 | </note> | ||
610 | </section> | ||
611 | |||
612 | <section id='sdk-generation-dev-environment'> | ||
613 | <title>SDK Generation</title> | ||
614 | |||
615 | <para> | ||
616 | The OpenEmbedded build system uses BitBake to generate the | ||
617 | Software Development Kit (SDK) installer script: | ||
618 | <imagedata fileref="figures/sdk-generation.png" align="center" width="6in" depth="7in" /> | ||
619 | </para> | ||
620 | |||
621 | <para> | ||
622 | Like image generation, the SDK script process consists of | ||
623 | several stages and depends on many variables. | ||
624 | The <filename>do_populate_sdk</filename> task uses these | ||
625 | key variables to help create the list of packages to actually | ||
626 | install. | ||
627 | </para> | ||
628 | |||
629 | <para> | ||
630 | The <filename>do_populate_sdk</filename> task handles two | ||
631 | parts: a target part and a host part. | ||
632 | The target part is the part built for the target hardware and | ||
633 | includes libraries and headers. | ||
634 | The host part is the part of the SDK that runs on the | ||
635 | <filename>SDKMACHINE</filename>. | ||
636 | </para> | ||
637 | |||
638 | <para> | ||
639 | Once both parts are constructed, the | ||
640 | <filename>do_populate_sdk</filename> task performs some cleanup | ||
641 | on both parts. | ||
642 | After the cleanup, the task creates a cross-development | ||
643 | environment setup script and any configuration files that | ||
644 | might be needed. | ||
645 | </para> | ||
646 | |||
647 | <para> | ||
648 | The final output of the task is the Cross-development | ||
649 | toolchain installation script (<filename>.sh</filename> file), | ||
650 | which includes the environment setup script. | ||
651 | </para> | ||
689 | </section> | 652 | </section> |
690 | </chapter> | 653 | </chapter> |