diff --git a/documentation/poky-ref-manual/ref-bitbake.xml b/documentation/poky-ref-manual/ref-bitbake.xml index cf019aabcd..1a98b048be 100644 --- a/documentation/poky-ref-manual/ref-bitbake.xml +++ b/documentation/poky-ref-manual/ref-bitbake.xml @@ -28,15 +28,15 @@ Parsing - The first thing BitBake does is work out its configuration by - looking for a file called bitbake.conf. - BitBake examines the BBPATH environment - variable looking for a conf/ - directory that contains a bitbake.conf file. - BitBake adds the first bitbake.conf file found in - BBPATH (similar to the PATH environment variable). - For Poky, bitbake.conf is found in meta/conf/. + BitBake parses configuration files, classes, and .bb files. + + + + The first thing BitBake does is look for the bitbake.conf file. + Poky keeps this file in meta/conf/. + BitBake finds it by examining the BBPATH environment + variable and looking for the meta/conf/ + directory. @@ -75,12 +75,12 @@ - After the parsing of the configuration files is complete, the + After classes are included, the variable BBFILES is set, usually in local.conf, and defines the list of places to search for .bb files. - By default this specifies the meta/packages/ + By default, the BBFILES variable specifies the meta/packages/ directory within Poky, but other directories such as meta-extras/ can be included too. @@ -92,19 +92,19 @@ BitBake parses each .bb file in BBFILES and stores the values of various variables. In summary, for each .bb - file the configuration + base class of variables are set, followed + file the configuration plus the base class of variables are set, followed by the data in the .bb file itself, followed by any inherit commands that .bb file might contain. - Parsing .bb files is a time - consuming process, so a cache is kept to speed up subsequent parsing. + Because parsing .bb files is a time + consuming process, a cache is kept to speed up subsequent parsing. This cache is invalid if the timestamp of the .bb - file itself has changed, or if the timestamps of any of the include, + file itself changes, or if the timestamps of any of the include, configuration or class files the .bb - file depends on have changed. + file depends on changes. @@ -113,58 +113,53 @@ Once all the .bb files have been - parsed, BitBake will proceed to build "poky-image-sato" (or whatever was - specified on the commandline) and looks for providers of that target. + parsed, BitBake starts to build the target (poky-image-sato in the previous section's + example) and looks for providers of that target. Once a provider is selected, BitBake resolves all the dependencies for - the target. In the case of "poky-image-sato", it would lead to - task-base.bb - which in turn would lead to packages like Contacts, - Dates, BusyBox - and these in turn depend on glibc and the toolchain. + the target. + In the case of "poky-image-sato", it would lead to task-base.bb, + which in turn leads to packages like Contacts, + Dates and BusyBox. + These packages in turn depend on glibc and the toolchain. - Sometimes a target might have multiple providers and a common example - is "virtual/kernel" that is provided by each kernel package. Each machine - will often elect the best provider of its kernel with a line like the + Sometimes a target might have multiple providers. + An common example is "virtual/kernel", which is provided by each kernel package. + Each machine often elects the best kernel provider by using a line similar to the following in the machine configuration file: - PREFERRED_PROVIDER_virtual/kernel = "linux-rp" + + +PREFERRED_PROVIDER_virtual/kernel = "linux-rp" + + - The default - PREFERRED_PROVIDER is the provider with the same name as - the target. + The default PREFERRED_PROVIDER + is the provider with the same name as the target. - Understanding how providers are chosen is complicated by the fact - multiple versions might be present. BitBake defaults to the highest - version of a provider by default. Version comparisons are made using - the same method as Debian. The PREFERRED_VERSION - variable can be used to specify a particular version - (usually in the distro configuration) but the order can - also be influenced by the DEFAULT_PREFERENCE - variable. By default files - have a preference of "0". Setting the - DEFAULT_PREFERENCE to "-1" will - make a package unlikely to be used unless it was explicitly referenced and - "1" makes it likely the package will be used. - PREFERRED_VERSION overrides - any DEFAULT_PREFERENCE. DEFAULT_PREFERENCE - is often used to mark more - experimental new versions of packages until they've undergone sufficient - testing to be considered stable. + Understanding how providers are chosen is made complicated by the fact + that multiple versions might exist. + BitBake defaults to the highest version of a provider. + Version comparisons are made using the same method as Debian. + You can use the PREFERRED_VERSION + variable to specify a particular version (usually in the distro configuration). + You can influence the order by using the + DEFAULT_PREFERENCE + variable. + By default, files have a preference of "0". + Setting the DEFAULT_PREFERENCE to "-1" makes the package unlikely to be used unless it is + explicitly referenced. + Setting the DEFAULT_PREFERENCE to "1" makes it likely the package is used. + PREFERRED_VERSION overrides any DEFAULT_PREFERENCE setting. + DEFAULT_PREFERENCE is often used to mark newer and more experimental package + versions until they have undergone sufficient testing to be considered stable. - The end result is that internally, BitBake has now built a list of - providers for each target it needs in order of priority. + In summary, BitBake has created a list of providers, which is prioritized, for each target. @@ -172,18 +167,20 @@ Dependencies - Each target BitBake builds consists of multiple tasks (e.g. fetch, - unpack, patch, configure, compile etc.). For best performance on - multi-core systems, BitBake considers each task as an independent - entity with a set of dependencies. There are many variables that - are used to signify these dependencies and more information can be found - about these in the - BitBake manual. At a basic level it is sufficient to know - that BitBake uses the DEPENDS and - RDEPENDS variables when - calculating dependencies and descriptions of these variables are - available through the links. + Each target BitBake builds consists of multiple tasks such as fetch, unpack, patch, configure, + and compile. + For best performance on multi-core systems, BitBake considers each task as an independent + entity with its own set of dependencies. + + + + Dependencies are defined through several variables. + You can find information about variables BitBake uses in the + BitBake manual. + At a basic level it is sufficient to know that BitBake uses the + DEPENDS and + RDEPENDS variables when + calculating dependencies. @@ -193,69 +190,75 @@ Based on the generated list of providers and the dependency information, - BitBake can now calculate exactly which tasks it needs to run and in what - order. The build now starts with BitBake forking off threads up to - the limit set in the BB_NUMBER_THREADS variable - as long as there are tasks ready to run, i.e. tasks with all their - dependencies met. + BitBake can now calculate exactly what tasks it needs to run and in what + order it needs to run them. + The build now starts with BitBake forking off threads up to the limit set in the + BB_NUMBER_THREADS variable. + BitBake continues to fork threads as long as there are tasks ready to run, + those taksks have all their dependencies met, and the thread threshold has not been + exceeded. - As each task completes, a timestamp is written to the directory - specified by the STAMPS variable (usually - build/tmp/stamps/*/). On - subsequent runs, BitBake looks at the STAMPS - directory and will not rerun - tasks its already completed unless a timestamp is found to be invalid. - Currently, invalid timestamps are only considered on a per .bb file basis so if for example the configure stamp has a timestamp greater than the - compile timestamp for a given target the compile task would rerun but this - has no effect on other providers depending on that target. This could - change or become configurable in future versions of BitBake. Some tasks - are marked as "nostamp" tasks which means no timestamp file will be written - and the task will always rerun. + As each task completes, a timestamp is written to the directory specified by the + STAMPS variable (usually + build/tmp/stamps/*/). + On subsequent runs, BitBake looks at the STAMPS directory and does not rerun + tasks that are already completed unless a timestamp is found to be invalid. + Currently, invalid timestamps are only considered on a per + .bb file basis. + So, for example, if the configure stamp has a timestamp greater than the + compile timestamp for a given target then the compile task would rerun. + Running the compile task again, however, has no effect on other providers + that depend on that target. + This behavior could change or become configurable in future versions of BitBake. - - Once all the tasks have been completed BitBake exits. - + + + Some tasks are marked as "nostamp" tasks. + No timestamp file is created when these tasks are run. + Consequently, "nostamp" tasks are always rerun. +
Running a Task - It's worth noting what BitBake does to run a task. A task can either - be a shell task or a python task. For shell tasks, BitBake writes a - shell script to ${WORKDIR}/temp/run.do_taskname.pid - and then executes the script. The generated - shell script contains all the exported variables, and the shell functions - with all variables expanded. Output from the shell script is - sent to the file ${WORKDIR}/temp/log.do_taskname.pid. - Looking at the - expanded shell functions in the run file and the output in the log files + Tasks can either be a shell task or a python task. + For shell tasks, BitBake writes a shell script to + ${WORKDIR}/temp/run.do_taskname.pid and then executes the script. + The generated shell script contains all the exported variables, and the shell functions + with all variables expanded. + Output from the shell script goes to the file ${WORKDIR}/temp/log.do_taskname.pid. + Looking at the expanded shell functions in the run file and the output in the log files is a useful debugging technique. - Python functions are executed internally to BitBake itself and - logging goes to the controlling terminal. Future versions of BitBake will - write the functions to files in a similar way to shell functions and - logging will also go to the log files in a similar way. + For Python tasks, BitBake executes the task internally and logs information to the + controlling terminal. + Future versions of BitBake will write the functions to files similar to the way + shell tasks are handled. + Logging will be handled in way similar to shell tasks as well. + + + Once all the tasks have been completed BitBake exits. +
- Commandline + BitBake Command Line - To quote from "bitbake --help": + Following is the bitbake manpage: - Usage: bitbake [options] [package ...] + +$ bitbake --help +Usage: bitbake [options] [package ...] Executes the specified task (default is 'build') for a given set of BitBake files. It expects that BBFILES is defined, which is a space separated list of files to @@ -275,6 +278,8 @@ Options: -a, --tryaltconfigs continue with builds by trying to use alternative providers where possible. -f, --force force run of specified cmd, regardless of stamp status + -i, --interactive drop into the interactive mode also called the BitBake + shell. -c CMD, --cmd=CMD Specify task to execute. Note that this only executes the specified task for the providee and the packages it depends on, i.e. 'compile' does not implicitly call @@ -287,9 +292,6 @@ Options: -D, --debug Increase the debug level. You can specify this more than once. -n, --dry-run don't execute, just go through the motions - -S, --dump-signatures - don't execute, just dump out the signature - construction information -p, --parse-only quit after parsing the BB files (developers only) -d, --disable-psyco disable using the psyco just-in-time compiler (not recommended) @@ -298,46 +300,45 @@ Options: what used to be bbread) -g, --graphviz emit the dependency trees of the specified packages in the dot syntax - -I EXTRA_ASSUME_PROVIDED, --ignore-deps=EXTRA_ASSUME_PROVIDED - Assume these dependencies don't exist and are already - provided (equivalent to ASSUME_PROVIDED). Useful to - make dependency graphs more appealing + -I IGNORED_DOT_DEPS, --ignore-deps=IGNORED_DOT_DEPS + Stop processing at the given list of dependencies when + generating dependency graphs. This can help to make + the graph more appealing -l DEBUG_DOMAINS, --log-domains=DEBUG_DOMAINS Show debug logging for the specified logging domains -P, --profile profile the command and print a report - -u UI, --ui=UI userinterface to use - --revisions-changed Set the exit code depending on whether upstream - floating revisions have changed or not - +
Fetchers - As well as the containing the parsing and task/dependency handling - code, BitBake also contains a set of "fetcher" modules which allow - fetching of source code from various types of sources. Example - sources might be from disk with the metadata, from websites, from - remote shell accounts or from SCM systems like cvs/subversion/git. + BitBake also contains a set of "fetcher" modules that allow + retrieval of source code from various types of sources. + For example, BitBake can get source code from a disk with the metadata, from websites, + from remote shell accounts or from Source Code Management (SCM) systems + like cvs/subversion/git. - The fetchers are usually triggered by entries in - SRC_URI. Information about the - options and formats of entries for specific fetchers can be found in the - BitBake manual. + Fetchers are usually triggered by entries in + SRC_URI. + You can find information about the options and formats of entries for specific + fetchers in the BitBake manual. One useful feature for certain SCM fetchers is the ability to - "auto-update" when the upstream SCM changes version. Since this - requires certain functionality from the SCM only certain systems - support it, currently Subversion, Bazaar and to a limited extent, Git. It - works using the SRCREV - variable. See the - developing with an external SCM based project section for more - information. + "auto-update" when the upstream SCM changes version. + Since this ability requires certain functionality from the SCM, not all + systems support it. + Currently Subversion, Bazaar and to a limited extent, Git support the ability to "auto-update". + This feature works using the SRCREV + variable. + See the + Developing within Poky with an External SCM-based Package + section for more information.