From c9f7865a347606a64696048817b0f09d9c3fcd31 Mon Sep 17 00:00:00 2001 From: Andrew Geissler Date: Fri, 18 Sep 2020 14:11:35 -0500 Subject: poky: subtree update:c67f57c09e..c6bc20857c MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Adrian Freihofer (2): oe-publish-sdk: fix layers init via ssh oe-publish-sdk: add --keep-orig option Alexander Kanavin (68): meta-selftest: correct the virgl test for 5.8 kernels bison: upgrade 3.6.4 -> 3.7.1 util-linux: upgrade 2.35.2 -> 2.36 python3-numpy: upgrade 1.19.0 -> 1.19.1 python3-setuptools: upgrade 49.3.1 -> 49.6.0 rsync: upgrade 3.2.2 -> 3.2.3 util-linux: merge .inc into .bb acpica: upgrade 20200528 -> 20200717 asciidoc: upgrade 9.0.1 -> 9.0.2 cryptodev: upgrade 1.10 -> 1.11 diffoscope: upgrade 153 -> 156 epiphany: upgrade 3.36.3 -> 3.36.4 font-alias: upgrade 1.0.3 -> 1.0.4 gtk+3: upgrade 3.24.21 -> 3.24.22 libcheck: upgrade 0.15.0 -> 0.15.2 libinput: upgrade 1.16.0 -> 1.16.1 libpipeline: upgrade 1.5.2 -> 1.5.3 libx11: upgrade 1.6.9 -> 1.6.11 linux-firmware: upgrade 20200619 -> 20200721 man-pages: upgrade 5.07 -> 5.08 mc: upgrade 4.8.24 -> 4.8.25 mesa: upgrade 20.1.4 -> 20.1.5 piglit: upgrade to latest revision re2c: upgrade 2.0 -> 2.0.2 sysstat: upgrade 12.2.2 -> 12.4.0 vala: upgrade 0.48.7 -> 0.48.9 bootchart2: update 0.14.8 -> 0.14.9 harfbuzz: convert to meson, enable gobject introspection pango: update 1.44.7 -> 1.46.0 boost: update 1.73.0 -> 1.74.0 xev: update 1.2.3 -> 1.2.4 wpebackend-fdo: update 1.6.1 -> 1.7.1 gpgme: update 1.13.1 -> 1.14.0 libpsl: update 0.21.0 -> 0.21.1. gettext: update 0.20.2 -> 0.21 cmake: update 3.17.3 -> 3.18.1 linux-firmware: update 20200721 -> 20200817 meson: update 0.55.0 -> 0.55.1 systemd-boot: bump version to 246.2 json-glib: inherit upstream-version-is-even packagegroup-core-device-devel: remove oeqa/x32lib: rework to use readelf from the host oeqa/multilib: rework to use readelf from the host oeqa/multilib: un-skip the connman test poky.conf: do not install packagegroup-core-device-devel into qemu images glib-2.0: update 2.64.4 -> 2.64.5 cmake: upgrade 3.18.1 -> 3.18.2 libxcrypt: upgrade 4.4.16 -> 4.4.17 debianutils: upgrade 4.11 -> 4.11.1 enchant2: upgrade 2.2.8 -> 2.2.9 harfbuzz: upgrade 2.7.1 -> 2.7.2 libmpc: upgrade 1.1.0 -> 1.2.0 librepo: upgrade 1.12.0 -> 1.12.1 libuv: upgrade 1.38.1 -> 1.39.0 msmtp: upgrade 1.8.11 -> 1.8.12 ninja: upgrade 1.10.0 -> 1.10.1 p11-kit: upgrade 0.23.20 -> 0.23.21 pango: upgrade 1.46.0 -> 1.46.1 re2c: upgrade 2.0.2 -> 2.0.3 resolvconf: upgrade 1.82 -> 1.83 stress-ng: upgrade 0.11.18 -> 0.11.19 gnu-config: update to latest revision nasm: update 2.15.03 -> 2.15.05 libva-utils: fix upstream version check gnupg: update 2.2.21 -> 2.2.22 libx11: update 1.6.11 -> 1.6.12 mesa: update 20.1.5 -> 20.1.6 xserver-xorg: update 1.20.8 -> 1.20.9 Andrey Zhizhikin (1): insane: check for missing update-alternatives inherit Anibal Limon (1): recipes-kernel: linux-firmware add qcom-venus-{5.2,5.4} packages Aníbal Limón (1): recipes-graphics/xorg-xserver: Add patch to fix segfault when probe Armin Kuster (2): bind: update to 9.11.22 ESV core-image-sato: qemumips use 512 mem Bruce Ashfield (30): linux-yocto/5.4: update to v5.4.59 linux-yocto/5.8: update to v5.8.2 yocto-bsp: update to v5.4.56 yocto-bsp: update to v5.4.58 qemu: bump default reference kernel to v5.8 linux-yocto/5.8: fix perf and virtio_scsi warnings linux-yocto-rt/5.8: fix lttng-modules build linux-yocto/5.8: selftests/bpf: Prevent runqslower from racing on building bpftool linux-yocto/5.8: disable CONFIG_NFS_DISABLE_UDP_SUPPORT poky: set preferred version for linux-yocto to be v5.8 poky-tiny: set preferred version to 5.8 poky: add preferred version for linux-yocto-rt linux-yocto/5.8: update to v5.8.3 linux-yocto/5.4: update to v5.4.60 kernel: config cleanups for 5.8+ linux-yocto/5.4: update to v5.4.61 linux-yocto/5.8: update to v5.8.4 linux-yocto/5.8: disable IKHEADERS in default builds kernel-yocto: allow promotion of configuration warnings to errors kernel-yocto: checksum all modifications to available kernel fragments directories lttng-modules/devupstream: bump to latest 2.12 commits linux-yocto-dev: bump to v5.9+ linux-yocto/5.8: update to v5.8.5 kernel-devsrc: account for HOSTCC and HOSTCXX linux-yocto/config: netfilter: Enable nat for ipv4 and ipv6 linux-yocto/5.8: update to v5.8.8 linux-yocto/5.4: update to v5.4.64 linux-yocto/config: configuration warning cleanup linux-yocto/5.8: update to v5.8.9 linux-yocto/5.4: update to v5.4.65 Changhyeok Bae (2): iw: upgrade 5.4 -> 5.8 iputils: upgrade s20190709 -> s20200821 Chris Laplante (12): bitbake: compat.py: remove file since it no longer actually implements anything bitbake: COW: formatting bitbake: COW: migrate test suite into tests/cow cve-update-db-native: add progress handler cve-check/cve-update-db-native: use lockfile to fix usage under multiconfig cve-update-db-native: use context manager for cve_f cve-check: avoid FileNotFoundError if no do_cve_check task has run bitbake: utils: process_profilelog: use context manager bitbake: utils: fix UnboundLocalError when _print_exception raises cve-update-db-native: be less magical about checking whether the cve-check class is enabled cve-update-db-native: move -journal checking into do_fetch cve-update-db-native: remove unused variable Christophe GUIBOUT (1): initramfs-framework: support kernel cmdline with double quotes Denys Dmytriyenko (2): weston: upgrade 8.0.0 -> 9.0.0 cryptodev: bump 1 commit past 1.11 to fix 5.9-rc1+ Diego Sueiro (2): license_image.bbclass: Create symlink to the image license manifest dir license_image.bbclass: Fix symlink to the image license manifest dir creation Douglas Royds (1): tcmode-default: Drop gcc-cross-initial, gcc-crosssdk-initial references Frazer Clews (1): bitbake: lib: fix most undefined code picked up by pylint Geoff Parker (1): systemd-serialgetty: Replace sed quoting using ' with " to allow var expansion Jacob Kroon (1): gcc10: Don't default back to -fcommon Jean-Francois Dagenais (1): bitbake: siggen: clean_basepath: remove recipe full path when virtual:xyz present Jens Rehsack (1): lttng-modules: backport patches from 2.12.x to fix 5.4.64+ and 5.8.9+ builds Joe Slater (1): pseudo: fix renaming to self Jon Mason (4): cortex-m0plus.inc: change file permissions tune-cortexa55.inc: clean-up ARMv8.2a uses tune-cortexa57-cortexa53.inc: add CRC and set march tune-cortexa*: Cleanups Joshua Watt (8): wic: Add 512 Byte alignment to --offset oeqa: runtime_tests: Extra GPG debugging oeqa: sdk: Capture stderr output oeqa: reproducible: Fix test not producing diffs diffoscope: upgrade 156 -> 158 bitbake: bitbake: Add parsing torture test bitbake: cooker: Block SIGINT in worker processes sphinx: dev-manual: Clarify that virtual providers do not apply to runtime dependencies Kai Kang (1): dhcpcd: 9.1.4 -> 9.2.0 Kevin Hao (1): meta-yocto-bsp: Bump to the v5.8 kernel Khairul Rohaizzat Jamaluddin (1): wic/bootimg-efi: IMAGE_EFI_BOOT_FILES variable added to separate bootimg-efi and bootimg-partition Khem Raj (24): gcc-cross-canadian: Install gcc/g++ wrappers for musl uninative: Upgrade to 2.9 packagegroup-core-tools-profile: Disable lttng-modules for riscv64 lttng-modules: Disable on riscv64 kexec-tools: Fix build with -fno-common on ppc lttng-tools: Do not build for riscv64 util-linux: Allow update alternatives for additional apps lttng-tools: lttng-ust works on riscv64 json-glib: Backport a build fix with clang rpcbind: Use update-alternatives for rpcinfo go: Upgrade to 1.15 major release weston-init: Redefine weston service and add socket activation option musl: Upgrade to latest master libucontext: Recognise riscv32 architecture linuxloader.bbclass: Define riscv32 ldso for musl populate_sdk_ext: Do not assume local.conf will always exist weston: plane_add_prop() calls break musl atomic modesetting weston-init: Enable RDP screen share weston-init: Do not use fbdev backend weston-init: Select drm/fbdev backends for qemu machines oeqa/weston: Fix tests to run with systemd core-image-weston: Bump qemu memory to 512M go: Update to 1.15.2 minor release bind: Inherit update-alternatives Mark Hatle (6): package_tar.bbclass: Sync to the other package_* classes kernel.bbclass: Remove do_install[prefunc] no longer needed buildhistory.bbclass: Rework to use read_subpackage_metadata kernel.bbclass: Move away from calling package_get_auto_pr package.bbclass: hash equivalency and pr service bitbake: process.py: Handle SystemExit exception to eliminate backtrace Mark Morton (1): sphinx: test-manual code block, link, and format update Martin Jansa (7): devtool: expand SRC_URI when guessing recipe update mode image-artifact-names: introduce new bbclass and move some variables into it kernel.bbclass: use bash variables like imageType, base_name without {} kernel.bbclass: eliminate (initramfs_)symlink_name variables kernel.bbclass: use camelCase notation for bash variables in do_deploy *-initramfs: don't use .rootfs IMAGE_NAME_SUFFIX bitbake.conf: use ${TCMODE}-${TCLIBC} directory for CACHE Matt Madison (1): image.bbclass: fix REPRODUCIBLE_TIMESTAMP_ROOTFS reference Michael Gloff (2): sysvinit rc: Use PSPLASH_FIFO_DIR for progress fifo sysvinit: Remove ${B} assignment Michael Tretter (1): devtool: deploy-target: Fix size calculation for hard links Ming Liu (2): systemd: split systemd specific udev rules into its own package libubootenv: inherit uboot-config Mingli Yu (3): qemu: always define unknown_lock_type qemu: override DEBUG_BUILD bison: remove the parallel build patch Naveen Saini (1): lib/oe/recipeutils.py: add support for BBFILES_DYNAMIC Nicolas Dechesne (73): linux-libc-headers: kernel headers are installed in STAGING_KERNEL_BUILDDIR bitbake: sphinx: add initial build infrastructure bitbake: sphinx: initial sphinx support bitbake: sphinx: bitbake-user-manual: use builtin sphinx glossary bitbake: sphinx: switch to readthedocs theme bitbake: sphinx: override theme CSS bitbake: sphinx: fixup for links bitbake: sphinx: fix links inside notes bitbake: sphinx: fixes all remaining warnings bitbake: sphinx: Makefile.sphinx: add clean and publish targets bitbake: sphinx: tweak html output a bit bitbake: sphinx: add SPDX headers bitbake: sphinx: index: move the boilerplate at the end of the page bitbake: sphinx: conf: enable extlinks extension bitbake: sphinx: add releases page bitbake: sphinx: bitbake-user-manual: insert additional blank line after title bitbake: sphinx: last manual round of fixes/improvements bitbake: sphinx: update style for important, caution and warnings bitbake: sphinx: remove leading '/' bitbake: sphinx: theme_override: properly set font for verbatim text bitbake: bitbake-user-manual: fix bad links sphinx: add initial build infrastructure sphinx: initial sphinx support sphinx: ref-variables: use builtin sphinx glossary sphinx: overview-manual: add figures sphinx: switch to readthedocs theme sphinx: Add SPDX license headers sphinx: add CSS theme override sphinx: bsp-guide: add figures sphinx: add Yocto project logo sphinx: conf: update copyright sphinx: conf: add substitutions/global variables sphinx: add boilerplate file sphinx: add boilerplate to manuals sphinx: ref-manual: add revision history table sphinx: add a general index sphinx: conf.py: enable sphinx.ext.autosectionlabel sphinx: ref-manual: use builtin glossary for the Terms section sphinx: fix internal links sphinx: ref-manual: fix typo sphinx: fix custom term links sphinx: manual updates for some links sphinx: dev-manual add figures sphinx: kernel-dev: add figures sphinx: profile-manual: add figures sphinx: fix up bold text for informalexample container sphinx: ref-manual: add figures sphinx: sdk-manual: add figures sphinx: test-manual: add figures sphinx: toaster-manual: add figures sphinx: add links for Yocto project website sphinx: fix links when the link text should be displayed sphinx: add links to terms in the BitBake glossary sphinx: add links to section in the Bitbake manual sphinx: setup extlink for docs.yoctoproject.org sphinx: enable intersphinx extension sphinx: insert blank below between title and toc sphinx: fix up terms related to kernel-fitimage sphinx: conf: a few rendering tweaks sphinx: makefile: add publish target sphinx: conf: include CSS/JS files, the proper way sphinx: convert 'what I wish I'd known' sphinx: convert 'transitioning to a custom environment' sphinx: ref-manual: fix heading for oe-init-build-env sphinx: brief-yoctoprojectqs: fix up all remaining rendering issues sphinx: Makefile.sphinx improvements sphinx: convert bsp-guide sphinx: remove leading '/' sphinx: update style for important, caution and warnings sphinx: profile-manual: convert profile-manual sphinx: theme_override: properly set font for verbatim text sphinx: theme_override: add tying-it-together admonition sphinx: conf: exclude adt-manual/*.rst Oleksandr Kravchuk (1): ell: update to 0.33 Ovidiu Panait (1): libxml2: Fix CVE-2020-24977 Peter A. Bigot (2): bluez5: fix builds that require ell support timezone: include leap second data in tzdata-core Peter Bergin (1): systemd: avoid failing if no udev rules provided Pierre-Jean Texier (2): libubootenv: upgrade 0.3 -> 0.3.1 diffoscope: upgrade 158 -> 160 Quentin Schulz (16): sphinx: brief-yoctoprojectqs: remove redundant welcome sphinx: brief-yoctoprojectqs: fix ambiguous note for cyclone5 example sphinx: brief-yoctoprojectqs: add missing boilerplate sphinx: overview-manual: add link to AUH how-to section sphinx: overview-manual: fix bitbake basic explanation sphinx: brief-yoctoprojectqs: add note on branch consistency between layers sphinx: what-i-wish-id-known: update "don't be fooled by doc search results" sphinx: overview-manual: remove highlight in bold section sphinx: replace special quotes with single and double quotes sphinx: fix incorrect indentations sphinx: brief-yoctoprojectqs: put other distros note after Ubuntu-specific packages sphinx: fix a few typos or missing/too many words sphinx: "highlight" some variables, tasks or files sphinx: fix or add missing links and remove mention of Eclipse workflow ref-manual: examples: hello-autotools: upgrade to 2.10 ref-manual: examples: libxpm: add relative path to .inc Rahul Kumar (1): systemd-serialgetty: Fix sed expression quoting Rasmus Villemoes (1): kernel.bbclass: run do_symlink_kernsrc before do_patch Richard Purdie (74): nativesdk-sdk-provides-dummy: Add /bin/sh bitbake: fetch2/wget: Remove buffering parameter bitbake: cooker: Ensure parse_quit thread is closed down bitbake: cooker: Explictly shut down the sync thread bitbake: fetch2: Drop cups.org from wget status checks bitbake: build/msg: Cleanup verbose option handling bitbake: cooker/cookerdata/main: Improve loglevel handling bitbake: cookerdata: Ensure UI options are updated to the server bitbake: cooker/cookerdata: Ensure UI event log is updated from commandline bitbake: cooker: Defer configuration init to after UI connection bitbake: server/process: Move the socket code to server process only bitbake: main/server/process: Drop configuration object passing bitbake: cooker: Ensure BB_ORIGENV is updated by changes to configuration.env bitbake: server/process: Log extra threads at exit bitbake: server/process: Add bitbake-server and exec() a new server process bitbake: runqueue: Don't use sys.argv bitbake: cooker: Ensure cooker's enviroment is updated on updateConfig connman-gnome/matchbox-desktop: Remove file:// globbing selftest/recipetool: Drop globbing SRC_URI test, no longer supported local.conf.sample: Document memory resident bitbake bitbake: fetch2: Drop globbing supprt in file:// SRC_URIs bitbake: server/process: Use sys.executable for bitbake-server bitbake: process: Avoid bb.utils.timeout bitbake: utils: Drop broken timeout function bitbake: server/process: Fix typo in code causing tracebacks oeqa/selftest: Apply patch to fix cpio build with -fno-common runqemu: Show an error for conflicting graphics options lttng: Move platform logic to dedicated inc file patchelf: upgrade 0.11 -> 0.12 build-appliance/packagegroup-core-base-utils: Replace dhcp-client/dhcp-server with dhcpcd/kea selftest/prservice: Improve test failure message iputils: Adapt ${PN}-tftpd package dependency to PACKAGECONFIG bitbake: process/knotty: Improve early exception handling bitbake: cooker/cookerdata: Use BBHandledException, not sys.exit() bitbake: cookerdata: Fix exception raise statements bitbake: process: Avoid printing binary strings for leftover processes bitbake: server/process: Ensure logging is flushed bitbake: server/process: Don't show tracebacks if the lockfile is removed bitbake: cooker: Ensure parser replacement calls parser final_cleanup bitbake: cooker: Assign a name to the sync thread to aid debugging bitbake: server/process: Ensure we don't keep looping if some other server is started bitbake: server/process: Prefix the log data with pid/time information bitbake: server/process: Note when commands complete in logs bitbake: cooker: Ensure parser is cleaned up runqemu: Add a hook to allow it to renice bitbake: cooker: Avoid parser deadlocks bitbake: cooker: Ensure parser worker signal handlers are default selftest/signing: Ensure build path relocation is safe oeqa/concurrencytest: Improve builddir path manipulations bitbake: cooker/command: Fix disconnection handling bitbake: tinfoil: Ensure sockets don't leak even when exceptions occur bitbake: tests/fetch: Move away from problematic freedesktop.org urls bitbake: sphinx: Enhance the sphinx experience/nagivation with: bitbake: sphinx: theme_override: Use bold for emphasis text Revert "qemu: always define unknown_lock_type" Revert "core-image-sato: qemumips use 512 mem" sphinx: Organize top level docs sphinx: releases.rst: Add index/links to docs for previous releases sphinx: boilerplate.rst: Drop versions notes as we have better navigation now sphinx: boilerplate.rst: Sphinx puts the copyright elsewhere sphinx: history: Move revision history to its own section sphinx: manuals: Move boilerplate after toctree sphinx: Add support for multiple docs version sphinx: index.rst: Fix links sphinx: ref-system-requirements: Improve formatting of the notes sections, merging them sphinx: ref-manual links fixes and many other cleanups to import sphinx: dev-manual: Various URL, code block and other fixes to imported data sphinx: sdk-manual: Various URL, code block and other fixes to imported data sphinx: kernel-dev: Various URL, code block and other fixes to imported data sphinx: theme_override: Use bold for emphasis text sphinx: ref-tasks: Add populate_sdk_ext task definition sphinx: ref-manual/migration: Split each release into its own file sphinx: overview-manual: Various URL, code block and other fixes to imported data build-appliance-image: Update to master head revision Robert Yang (3): bitbake: cooker.py: Save prioritized BBFILES to BBFILES_PRIORITIZED bitbake: utils.py: get_file_layer(): Exit the loop when file is matched bitbake: utils.py: get_file_layer(): Improve performance Ross Burton (25): package.bbclass: explode the RPROVIDES so we don't think the versions are provides elfutils: silence a new QA warning insane: improve gnu-hash-style warning gdk-pixbuf: add tests PACKAGECONFIG debianutils: change SRC_URI to use snapshot.debian.org insane: only load real files as ELF autoconf: consolidate SRC_URI autoconf: consolidate DEPENDS kea: no need to depend on kea-native kea: don't use PACKAGECONFIG inappropriately kea: bump to 1.7.10 help2man: rewrite recipe local.conf.sample.extended: remove help2man reference curl: add vendors to CVE_PRODUCT to exclude false positives harfbuzz: update patch status harfbuzz: fix a build race around hb-version.h cmake: whitelist CVE-2016-10642 ncurses: remove config.cache qemu: fix CVE-2020-14364 cve-update-db-native: remove unused import cve-update-db-native: add more logging when fetching cve-update-db-native: use fetch task alsa-plugins: improve .la removal sato-screenshot: improve .la removal buildhistory-diff: use BUILDDIR to know where buildhistory is Saul Wold (1): gnupg: uprev 2.2.22 -> 2.2.23 Stacy Gaikovaia (2): bison: uprev from 3.7.1 to 3.7.2 valgrind: fix memcheck vgtests remove fullpath-after flags Steve Sakoman (1): xinput-calibrator: change SRC_URI to branch with libinput support Sumit Garg (1): insane: fix gnu-hash-style check TeohJayShen (1): oeqa/runtime: add test for matchbox-terminal Tim Orling (1): sphinx: toaster-manual: fix vars, links, code blocks Vijai Kumar K (2): image_types_wic: Add ASSUME_PROVIDED to WICVARS wic: misc: Add /bin to the list of searchpaths Yanfei Xu (1): kernel-yocto: only replace leading -I in include paths Yi Zhao (1): glib-networking: add ptest Zhixiong Chi (1): gnutls: CVE-2020-24659 akuster (8): log4cplus: move meta-oe pkg to core kea: Move from meta-networking maintainers.inc: Add me as kea & log4plus maintainer. dhcpcd: Move from meta-network as OE-Core needs a client maintainers.inc: Add me as dhcpcd maintainer dhcp: remove from core bind: Add 9.16.x bind: 9.11 remove hongxu (1): sysstat: fix installed-vs-shipped QA Issue in systemd zangrc (4): libcap:upgrade 2.42 -> 2.43 libcap-ng:upgrade 0.7.10 -> 0.7.11 libgpg-error:upgrade 1.38 -> 1.39 at-spi2-core:upgrade 2.36.0 -> 2.36.1 Signed-off-by: Andrew Geissler Change-Id: I5542f5eea751a2641342e945725fd687cd74bebe --- .../overview-manual/overview-manual-concepts.rst | 2185 ++++++++++++++++++++ 1 file changed, 2185 insertions(+) create mode 100644 poky/documentation/overview-manual/overview-manual-concepts.rst (limited to 'poky/documentation/overview-manual/overview-manual-concepts.rst') diff --git a/poky/documentation/overview-manual/overview-manual-concepts.rst b/poky/documentation/overview-manual/overview-manual-concepts.rst new file mode 100644 index 0000000000..3d8dc7afd1 --- /dev/null +++ b/poky/documentation/overview-manual/overview-manual-concepts.rst @@ -0,0 +1,2185 @@ +.. SPDX-License-Identifier: CC-BY-2.0-UK + +********************** +Yocto Project Concepts +********************** + +This chapter provides explanations for Yocto Project concepts that go +beyond the surface of "how-to" information and reference (or look-up) +material. Concepts such as components, the :term:`OpenEmbedded Build System` +workflow, +cross-development toolchains, shared state cache, and so forth are +explained. + +Yocto Project Components +======================== + +The :term:`BitBake` task executor +together with various types of configuration files form the +:term:`OpenEmbedded-Core (OE-Core)`. This section +overviews these components by describing their use and how they +interact. + +BitBake handles the parsing and execution of the data files. The data +itself is of various types: + +- *Recipes:* Provides details about particular pieces of software. + +- *Class Data:* Abstracts common build information (e.g. how to build a + Linux kernel). + +- *Configuration Data:* Defines machine-specific settings, policy + decisions, and so forth. Configuration data acts as the glue to bind + everything together. + +BitBake knows how to combine multiple data sources together and refers +to each data source as a layer. For information on layers, see the +":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`" +section of the Yocto Project Development Tasks Manual. + +Following are some brief details on these core components. For +additional information on how these components interact during a build, +see the +":ref:`overview-manual/overview-manual-concepts:openembedded build system concepts`" +section. + +.. _usingpoky-components-bitbake: + +BitBake +------- + +BitBake is the tool at the heart of the :term:`OpenEmbedded Build System` +and is responsible +for parsing the :term:`Metadata`, generating +a list of tasks from it, and then executing those tasks. + +This section briefly introduces BitBake. If you want more information on +BitBake, see the :doc:`BitBake User Manual `. + +To see a list of the options BitBake supports, use either of the +following commands: +:: + + $ bitbake -h + $ bitbake --help + +The most common usage for BitBake is ``bitbake recipename``, where +``recipename`` is the name of the recipe you want to build (referred +to as the "target"). The target often equates to the first part of a +recipe's filename (e.g. "foo" for a recipe named ``foo_1.3.0-r0.bb``). +So, to process the ``matchbox-desktop_1.2.3.bb`` recipe file, you might +type the following: +:: + + $ bitbake matchbox-desktop + +Several different +versions of ``matchbox-desktop`` might exist. BitBake chooses the one +selected by the distribution configuration. You can get more details +about how BitBake chooses between different target versions and +providers in the +":ref:`Preferences `" section +of the BitBake User Manual. + +BitBake also tries to execute any dependent tasks first. So for example, +before building ``matchbox-desktop``, BitBake would build a cross +compiler and ``glibc`` if they had not already been built. + +A useful BitBake option to consider is the ``-k`` or ``--continue`` +option. This option instructs BitBake to try and continue processing the +job as long as possible even after encountering an error. When an error +occurs, the target that failed and those that depend on it cannot be +remade. However, when you use this option other dependencies can still +be processed. + +.. _overview-components-recipes: + +Recipes +------- + +Files that have the ``.bb`` suffix are "recipes" files. In general, a +recipe contains information about a single piece of software. This +information includes the location from which to download the unaltered +source, any source patches to be applied to that source (if needed), +which special configuration options to apply, how to compile the source +files, and how to package the compiled output. + +The term "package" is sometimes used to refer to recipes. However, since +the word "package" is used for the packaged output from the OpenEmbedded +build system (i.e. ``.ipk`` or ``.deb`` files), this document avoids +using the term "package" when referring to recipes. + +.. _overview-components-classes: + +Classes +------- + +Class files (``.bbclass``) contain information that is useful to share +between recipes files. An example is the +:ref:`autotools ` class, +which contains common settings for any application that Autotools uses. +The ":ref:`ref-manual/ref-classes:Classes`" chapter in the +Yocto Project Reference Manual provides details about classes and how to +use them. + +.. _overview-components-configurations: + +Configurations +-------------- + +The configuration files (``.conf``) define various configuration +variables that govern the OpenEmbedded build process. These files fall +into several areas that define machine configuration options, +distribution configuration options, compiler tuning options, general +common configuration options, and user configuration options in +``conf/local.conf``, which is found in the :term:`Build Directory`. + + +.. _overview-layers: + +Layers +====== + +Layers are repositories that contain related metadata (i.e. sets of +instructions) that tell the OpenEmbedded build system how to build a +target. Yocto Project's `layer model <#the-yocto-project-layer-model>`__ +facilitates collaboration, sharing, customization, and reuse within the +Yocto Project development environment. Layers logically separate +information for your project. For example, you can use a layer to hold +all the configurations for a particular piece of hardware. Isolating +hardware-specific configurations allows you to share other metadata by +using a different layer where that metadata might be common across +several pieces of hardware. + +Many layers exist that work in the Yocto Project development +environment. The `Yocto Project Curated Layer +Index `__ +and `OpenEmbedded Layer +Index `__ +both contain layers from which you can use or leverage. + +By convention, layers in the Yocto Project follow a specific form. +Conforming to a known structure allows BitBake to make assumptions +during builds on where to find types of metadata. You can find +procedures and learn about tools (i.e. ``bitbake-layers``) for creating +layers suitable for the Yocto Project in the +":ref:`dev-manual/dev-manual-common-tasks:understanding and creating layers`" +section of the Yocto Project Development Tasks Manual. + +.. _openembedded-build-system-build-concepts: + +OpenEmbedded Build System Concepts +================================== + +This section takes a more detailed look inside the build process used by +the :term:`OpenEmbedded Build System`, +which is the build +system specific to the Yocto Project. At the heart of the build system +is BitBake, the task executor. + +The following diagram represents the high-level workflow of a build. The +remainder of this section expands on the fundamental input, output, +process, and metadata logical blocks that make up the workflow. + +.. image:: figures/YP-flow-diagram.png + :align: center + +In general, the build's workflow consists of several functional areas: + +- *User Configuration:* metadata you can use to control the build + process. + +- *Metadata Layers:* Various layers that provide software, machine, and + distro metadata. + +- *Source Files:* Upstream releases, local projects, and SCMs. + +- *Build System:* Processes under the control of + :term:`BitBake`. This block expands + on how BitBake fetches source, applies patches, completes + compilation, analyzes output for package generation, creates and + tests packages, generates images, and generates cross-development + tools. + +- *Package Feeds:* Directories containing output packages (RPM, DEB or + IPK), which are subsequently used in the construction of an image or + Software Development Kit (SDK), produced by the build system. These + feeds can also be copied and shared using a web server or other means + to facilitate extending or updating existing images on devices at + runtime if runtime package management is enabled. + +- *Images:* Images produced by the workflow. + +- *Application Development SDK:* Cross-development tools that are + produced along with an image or separately with BitBake. + +User Configuration +------------------ + +User configuration helps define the build. Through user configuration, +you can tell BitBake the target architecture for which you are building +the image, where to store downloaded source, and other build properties. + +The following figure shows an expanded representation of the "User +Configuration" box of the `general workflow +figure <#general-workflow-figure>`__: + +.. image:: figures/user-configuration.png + :align: center + +BitBake needs some basic configuration files in order to complete a +build. These files are ``*.conf`` files. The minimally necessary ones +reside as example files in the ``build/conf`` directory of the +:term:`Source Directory`. For simplicity, +this section refers to the Source Directory as the "Poky Directory." + +When you clone the :term:`Poky` Git repository +or you download and unpack a Yocto Project release, you can set up the +Source Directory to be named anything you want. For this discussion, the +cloned repository uses the default name ``poky``. + +.. note:: + + The Poky repository is primarily an aggregation of existing + repositories. It is not a canonical upstream source. + +The ``meta-poky`` layer inside Poky contains a ``conf`` directory that +has example configuration files. These example files are used as a basis +for creating actual configuration files when you source +:ref:`structure-core-script`, which is the +build environment script. + +Sourcing the build environment script creates a +:term:`Build Directory` if one does not +already exist. BitBake uses the Build Directory for all its work during +builds. The Build Directory has a ``conf`` directory that contains +default versions of your ``local.conf`` and ``bblayers.conf`` +configuration files. These default configuration files are created only +if versions do not already exist in the Build Directory at the time you +source the build environment setup script. + +Because the Poky repository is fundamentally an aggregation of existing +repositories, some users might be familiar with running the +:ref:`structure-core-script` script in the context of separate +:term:`OpenEmbedded-Core (OE-Core)` and BitBake +repositories rather than a single Poky repository. This discussion +assumes the script is executed from within a cloned or unpacked version +of Poky. + +Depending on where the script is sourced, different sub-scripts are +called to set up the Build Directory (Yocto or OpenEmbedded). +Specifically, the script ``scripts/oe-setup-builddir`` inside the poky +directory sets up the Build Directory and seeds the directory (if +necessary) with configuration files appropriate for the Yocto Project +development environment. + +.. note:: + + The + scripts/oe-setup-builddir + script uses the + ``$TEMPLATECONF`` + variable to determine which sample configuration files to locate. + +The ``local.conf`` file provides many basic variables that define a +build environment. Here is a list of a few. To see the default +configurations in a ``local.conf`` file created by the build environment +script, see the +:yocto_git:`local.conf.sample ` +in the ``meta-poky`` layer: + +- *Target Machine Selection:* Controlled by the + :term:`MACHINE` variable. + +- *Download Directory:* Controlled by the + :term:`DL_DIR` variable. + +- *Shared State Directory:* Controlled by the + :term:`SSTATE_DIR` variable. + +- *Build Output:* Controlled by the + :term:`TMPDIR` variable. + +- *Distribution Policy:* Controlled by the + :term:`DISTRO` variable. + +- *Packaging Format:* Controlled by the + :term:`PACKAGE_CLASSES` + variable. + +- *SDK Target Architecture:* Controlled by the + :term:`SDKMACHINE` variable. + +- *Extra Image Packages:* Controlled by the + :term:`EXTRA_IMAGE_FEATURES` + variable. + +.. note:: + + Configurations set in the + conf/local.conf + file can also be set in the + conf/site.conf + and + conf/auto.conf + configuration files. + +The ``bblayers.conf`` file tells BitBake what layers you want considered +during the build. By default, the layers listed in this file include +layers minimally needed by the build system. However, you must manually +add any custom layers you have created. You can find more information on +working with the ``bblayers.conf`` file in the +":ref:`dev-manual/dev-manual-common-tasks:enabling your layer`" +section in the Yocto Project Development Tasks Manual. + +The files ``site.conf`` and ``auto.conf`` are not created by the +environment initialization script. If you want the ``site.conf`` file, +you need to create that yourself. The ``auto.conf`` file is typically +created by an autobuilder: + +- *site.conf:* You can use the ``conf/site.conf`` configuration + file to configure multiple build directories. For example, suppose + you had several build environments and they shared some common + features. You can set these default build properties here. A good + example is perhaps the packaging format to use through the + :term:`PACKAGE_CLASSES` + variable. + + One useful scenario for using the ``conf/site.conf`` file is to + extend your :term:`BBPATH` variable + to include the path to a ``conf/site.conf``. Then, when BitBake looks + for Metadata using ``BBPATH``, it finds the ``conf/site.conf`` file + and applies your common configurations found in the file. To override + configurations in a particular build directory, alter the similar + configurations within that build directory's ``conf/local.conf`` + file. + +- *auto.conf:* The file is usually created and written to by an + autobuilder. The settings put into the file are typically the same as + you would find in the ``conf/local.conf`` or the ``conf/site.conf`` + files. + +You can edit all configuration files to further define any particular +build environment. This process is represented by the "User +Configuration Edits" box in the figure. + +When you launch your build with the ``bitbake target`` command, BitBake +sorts out the configurations to ultimately define your build +environment. It is important to understand that the +:term:`OpenEmbedded Build System` reads the +configuration files in a specific order: ``site.conf``, ``auto.conf``, +and ``local.conf``. And, the build system applies the normal assignment +statement rules as described in the +":doc:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata`" chapter +of the BitBake User Manual. Because the files are parsed in a specific +order, variable assignments for the same variable could be affected. For +example, if the ``auto.conf`` file and the ``local.conf`` set variable1 +to different values, because the build system parses ``local.conf`` +after ``auto.conf``, variable1 is assigned the value from the +``local.conf`` file. + +Metadata, Machine Configuration, and Policy Configuration +--------------------------------------------------------- + +The previous section described the user configurations that define +BitBake's global behavior. This section takes a closer look at the +layers the build system uses to further control the build. These layers +provide Metadata for the software, machine, and policies. + +In general, three types of layer input exists. You can see them below +the "User Configuration" box in the `general workflow +figure <#general-workflow-figure>`__: + +- *Metadata (.bb + Patches):* Software layers containing + user-supplied recipe files, patches, and append files. A good example + of a software layer might be the + `meta-qt5 layer `__ from + the `OpenEmbedded Layer + Index `__. + This layer is for version 5.0 of the popular + `Qt `__ cross-platform application + development framework for desktop, embedded and mobile. + +- *Machine BSP Configuration:* Board Support Package (BSP) layers (i.e. + "BSP Layer" in the following figure) providing machine-specific + configurations. This type of information is specific to a particular + target architecture. A good example of a BSP layer from the `Poky + Reference Distribution <#gs-reference-distribution-poky>`__ is the + :yocto_git:`meta-yocto-bsp ` + layer. + +- *Policy Configuration:* Distribution Layers (i.e. "Distro Layer" in + the following figure) providing top-level or general policies for the + images or SDKs being built for a particular distribution. For + example, in the Poky Reference Distribution the distro layer is the + :yocto_git:`meta-poky ` + layer. Within the distro layer is a ``conf/distro`` directory that + contains distro configuration files (e.g. + :yocto_git:`poky.conf ` + that contain many policy configurations for the Poky distribution. + +The following figure shows an expanded representation of these three +layers from the `general workflow figure <#general-workflow-figure>`__: + +.. image:: figures/layer-input.png + :align: center + +In general, all layers have a similar structure. They all contain a +licensing file (e.g. ``COPYING.MIT``) if the layer is to be distributed, +a ``README`` file as good practice and especially if the layer is to be +distributed, a configuration directory, and recipe directories. You can +learn about the general structure for layers used with the Yocto Project +in the +":ref:`dev-manual/dev-manual-common-tasks:creating your own layer`" +section in the +Yocto Project Development Tasks Manual. For a general discussion on +layers and the many layers from which you can draw, see the +"`Layers <#overview-layers>`__" and "`The Yocto Project Layer +Model <#the-yocto-project-layer-model>`__" sections both earlier in this +manual. + +If you explored the previous links, you discovered some areas where many +layers that work with the Yocto Project exist. The `Source +Repositories `__ also shows layers +categorized under "Yocto Metadata Layers." + +.. note:: + + Layers exist in the Yocto Project Source Repositories that cannot be + found in the OpenEmbedded Layer Index. These layers are either + deprecated or experimental in nature. + +BitBake uses the ``conf/bblayers.conf`` file, which is part of the user +configuration, to find what layers it should be using as part of the +build. + +Distro Layer +~~~~~~~~~~~~ + +The distribution layer provides policy configurations for your +distribution. Best practices dictate that you isolate these types of +configurations into their own layer. Settings you provide in +``conf/distro/distro.conf`` override similar settings that BitBake finds +in your ``conf/local.conf`` file in the Build Directory. + +The following list provides some explanation and references for what you +typically find in the distribution layer: + +- *classes:* Class files (``.bbclass``) hold common functionality that + can be shared among recipes in the distribution. When your recipes + inherit a class, they take on the settings and functions for that + class. You can read more about class files in the + ":ref:`ref-manual/ref-classes:Classes`" chapter of the Yocto + Reference Manual. + +- *conf:* This area holds configuration files for the layer + (``conf/layer.conf``), the distribution + (``conf/distro/distro.conf``), and any distribution-wide include + files. + +- *recipes-*:* Recipes and append files that affect common + functionality across the distribution. This area could include + recipes and append files to add distribution-specific configuration, + initialization scripts, custom image recipes, and so forth. Examples + of ``recipes-*`` directories are ``recipes-core`` and + ``recipes-extra``. Hierarchy and contents within a ``recipes-*`` + directory can vary. Generally, these directories contain recipe files + (``*.bb``), recipe append files (``*.bbappend``), directories that + are distro-specific for configuration files, and so forth. + +BSP Layer +~~~~~~~~~ + +The BSP Layer provides machine configurations that target specific +hardware. Everything in this layer is specific to the machine for which +you are building the image or the SDK. A common structure or form is +defined for BSP layers. You can learn more about this structure in the +:doc:`../bsp-guide/bsp-guide`. + +.. note:: + + In order for a BSP layer to be considered compliant with the Yocto + Project, it must meet some structural requirements. + +The BSP Layer's configuration directory contains configuration files for +the machine (``conf/machine/machine.conf``) and, of course, the layer +(``conf/layer.conf``). + +The remainder of the layer is dedicated to specific recipes by function: +``recipes-bsp``, ``recipes-core``, ``recipes-graphics``, +``recipes-kernel``, and so forth. Metadata can exist for multiple +formfactors, graphics support systems, and so forth. + +.. note:: + + While the figure shows several + recipes-\* + directories, not all these directories appear in all BSP layers. + +Software Layer +~~~~~~~~~~~~~~ + +The software layer provides the Metadata for additional software +packages used during the build. This layer does not include Metadata +that is specific to the distribution or the machine, which are found in +their respective layers. + +This layer contains any recipes, append files, and patches, that your +project needs. + +.. _sources-dev-environment: + +Sources +------- + +In order for the OpenEmbedded build system to create an image or any +target, it must be able to access source files. The `general workflow +figure <#general-workflow-figure>`__ represents source files using the +"Upstream Project Releases", "Local Projects", and "SCMs (optional)" +boxes. The figure represents mirrors, which also play a role in locating +source files, with the "Source Materials" box. + +The method by which source files are ultimately organized is a function +of the project. For example, for released software, projects tend to use +tarballs or other archived files that can capture the state of a release +guaranteeing that it is statically represented. On the other hand, for a +project that is more dynamic or experimental in nature, a project might +keep source files in a repository controlled by a Source Control Manager +(SCM) such as Git. Pulling source from a repository allows you to +control the point in the repository (the revision) from which you want +to build software. Finally, a combination of the two might exist, which +would give the consumer a choice when deciding where to get source +files. + +BitBake uses the :term:`SRC_URI` +variable to point to source files regardless of their location. Each +recipe must have a ``SRC_URI`` variable that points to the source. + +Another area that plays a significant role in where source files come +from is pointed to by the +:term:`DL_DIR` variable. This area is +a cache that can hold previously downloaded source. You can also +instruct the OpenEmbedded build system to create tarballs from Git +repositories, which is not the default behavior, and store them in the +``DL_DIR`` by using the +:term:`BB_GENERATE_MIRROR_TARBALLS` +variable. + +Judicious use of a ``DL_DIR`` directory can save the build system a trip +across the Internet when looking for files. A good method for using a +download directory is to have ``DL_DIR`` point to an area outside of +your Build Directory. Doing so allows you to safely delete the Build +Directory if needed without fear of removing any downloaded source file. + +The remainder of this section provides a deeper look into the source +files and the mirrors. Here is a more detailed look at the source file +area of the `general workflow figure <#general-workflow-figure>`__: + +.. image:: figures/source-input.png + :align: center + +Upstream Project Releases +~~~~~~~~~~~~~~~~~~~~~~~~~ + +Upstream project releases exist anywhere in the form of an archived file +(e.g. tarball or zip file). These files correspond to individual +recipes. For example, the figure uses specific releases each for +BusyBox, Qt, and Dbus. An archive file can be for any released product +that can be built using a recipe. + +Local Projects +~~~~~~~~~~~~~~ + +Local projects are custom bits of software the user provides. These bits +reside somewhere local to a project - perhaps a directory into which the +user checks in items (e.g. a local directory containing a development +source tree used by the group). + +The canonical method through which to include a local project is to use +the :ref:`externalsrc ` +class to include that local project. You use either the ``local.conf`` +or a recipe's append file to override or set the recipe to point to the +local directory on your disk to pull in the whole source tree. + +.. _scms: + +Source Control Managers (Optional) +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Another place from which the build system can get source files is with +:ref:`fetchers ` employing various Source +Control Managers (SCMs) such as Git or Subversion. In such cases, a +repository is cloned or checked out. The +:ref:`ref-tasks-fetch` task inside +BitBake uses the :term:`SRC_URI` +variable and the argument's prefix to determine the correct fetcher +module. + +.. note:: + + For information on how to have the OpenEmbedded build system generate + tarballs for Git repositories and place them in the + DL_DIR + directory, see the :term:`BB_GENERATE_MIRROR_TARBALLS` + variable in the Yocto Project Reference Manual. + +When fetching a repository, BitBake uses the +:term:`SRCREV` variable to determine +the specific revision from which to build. + +Source Mirror(s) +~~~~~~~~~~~~~~~~ + +Two kinds of mirrors exist: pre-mirrors and regular mirrors. The +:term:`PREMIRRORS` and +:term:`MIRRORS` variables point to +these, respectively. BitBake checks pre-mirrors before looking upstream +for any source files. Pre-mirrors are appropriate when you have a shared +directory that is not a directory defined by the +:term:`DL_DIR` variable. A Pre-mirror +typically points to a shared directory that is local to your +organization. + +Regular mirrors can be any site across the Internet that is used as an +alternative location for source code should the primary site not be +functioning for some reason or another. + +.. _package-feeds-dev-environment: + +Package Feeds +------------- + +When the OpenEmbedded build system generates an image or an SDK, it gets +the packages from a package feed area located in the +:term:`Build Directory`. The `general +workflow figure <#general-workflow-figure>`__ shows this package feeds +area in the upper-right corner. + +This section looks a little closer into the package feeds area used by +the build system. Here is a more detailed look at the area: + +.. image:: figures/package-feeds.png + :align: center + +Package feeds are an intermediary step in the build process. The +OpenEmbedded build system provides classes to generate different package +types, and you specify which classes to enable through the +:term:`PACKAGE_CLASSES` +variable. Before placing the packages into package feeds, the build +process validates them with generated output quality assurance checks +through the :ref:`insane ` +class. + +The package feed area resides in the Build Directory. The directory the +build system uses to temporarily store packages is determined by a +combination of variables and the particular package manager in use. See +the "Package Feeds" box in the illustration and note the information to +the right of that area. In particular, the following defines where +package files are kept: + +- :term:`DEPLOY_DIR`: Defined as + ``tmp/deploy`` in the Build Directory. + +- ``DEPLOY_DIR_*``: Depending on the package manager used, the package + type sub-folder. Given RPM, IPK, or DEB packaging and tarball + creation, the + :term:`DEPLOY_DIR_RPM`, + :term:`DEPLOY_DIR_IPK`, + :term:`DEPLOY_DIR_DEB`, or + :term:`DEPLOY_DIR_TAR`, + variables are used, respectively. + +- :term:`PACKAGE_ARCH`: Defines + architecture-specific sub-folders. For example, packages could exist + for the i586 or qemux86 architectures. + +BitBake uses the +:ref:`do_package_write_* ` +tasks to generate packages and place them into the package holding area +(e.g. ``do_package_write_ipk`` for IPK packages). See the +":ref:`ref-tasks-package_write_deb`", +":ref:`ref-tasks-package_write_ipk`", +":ref:`ref-tasks-package_write_rpm`", +and +":ref:`ref-tasks-package_write_tar`" +sections in the Yocto Project Reference Manual for additional +information. As an example, consider a scenario where an IPK packaging +manager is being used and package architecture support for both i586 and +qemux86 exist. Packages for the i586 architecture are placed in +``build/tmp/deploy/ipk/i586``, while packages for the qemux86 +architecture are placed in ``build/tmp/deploy/ipk/qemux86``. + +.. _bitbake-dev-environment: + +BitBake Tool +------------ + +The OpenEmbedded build system uses +:term:`BitBake` to produce images and +Software Development Kits (SDKs). You can see from the `general workflow +figure <#general-workflow-figure>`__, the BitBake area consists of +several functional areas. This section takes a closer look at each of +those areas. + +.. note:: + + Separate documentation exists for the BitBake tool. See the + BitBake User Manual + for reference material on BitBake. + +.. _source-fetching-dev-environment: + +Source Fetching +~~~~~~~~~~~~~~~ + +The first stages of building a recipe are to fetch and unpack the source +code: + +.. image:: figures/source-fetching.png + :align: center + +The :ref:`ref-tasks-fetch` and +:ref:`ref-tasks-unpack` tasks fetch +the source files and unpack them into the +:term:`Build Directory`. + +.. note:: + + For every local file (e.g. + file:// + ) that is part of a recipe's + SRC_URI + statement, the OpenEmbedded build system takes a checksum of the file + for the recipe and inserts the checksum into the signature for the + do_fetch + task. If any local file has been modified, the + do_fetch + task and all tasks that depend on it are re-executed. + +By default, everything is accomplished in the Build Directory, which has +a defined structure. For additional general information on the Build +Directory, see the ":ref:`structure-core-build`" section in +the Yocto Project Reference Manual. + +Each recipe has an area in the Build Directory where the unpacked source +code resides. The :term:`S` variable points +to this area for a recipe's unpacked source code. The name of that +directory for any given recipe is defined from several different +variables. The preceding figure and the following list describe the +Build Directory's hierarchy: + +- :term:`TMPDIR`: The base directory + where the OpenEmbedded build system performs all its work during the + build. The default base directory is the ``tmp`` directory. + +- :term:`PACKAGE_ARCH`: The + architecture of the built package or packages. Depending on the + eventual destination of the package or packages (i.e. machine + architecture, :term:`Build Host`, SDK, or + specific machine), ``PACKAGE_ARCH`` varies. See the variable's + description for details. + +- :term:`TARGET_OS`: The operating + system of the target device. A typical value would be "linux" (e.g. + "qemux86-poky-linux"). + +- :term:`PN`: The name of the recipe used + to build the package. This variable can have multiple meanings. + However, when used in the context of input files, ``PN`` represents + the name of the recipe. + +- :term:`WORKDIR`: The location + where the OpenEmbedded build system builds a recipe (i.e. does the + work to create the package). + + - :term:`PV`: The version of the + recipe used to build the package. + + - :term:`PR`: The revision of the + recipe used to build the package. + +- :term:`S`: Contains the unpacked source + files for a given recipe. + + - :term:`BPN`: The name of the recipe + used to build the package. The ``BPN`` variable is a version of + the ``PN`` variable but with common prefixes and suffixes removed. + + - :term:`PV`: The version of the + recipe used to build the package. + +.. note:: + + In the previous figure, notice that two sample hierarchies exist: one + based on package architecture (i.e. + PACKAGE_ARCH + ) and one based on a machine (i.e. + MACHINE + ). The underlying structures are identical. The differentiator being + what the OpenEmbedded build system is using as a build target (e.g. + general architecture, a build host, an SDK, or a specific machine). + +.. _patching-dev-environment: + +Patching +~~~~~~~~ + +Once source code is fetched and unpacked, BitBake locates patch files +and applies them to the source files: + +.. image:: figures/patching.png + :align: center + +The :ref:`ref-tasks-patch` task uses a +recipe's :term:`SRC_URI` statements +and the :term:`FILESPATH` variable +to locate applicable patch files. + +Default processing for patch files assumes the files have either +``*.patch`` or ``*.diff`` file types. You can use ``SRC_URI`` parameters +to change the way the build system recognizes patch files. See the +:ref:`ref-tasks-patch` task for more +information. + +BitBake finds and applies multiple patches for a single recipe in the +order in which it locates the patches. The ``FILESPATH`` variable +defines the default set of directories that the build system uses to +search for patch files. Once found, patches are applied to the recipe's +source files, which are located in the +:term:`S` directory. + +For more information on how the source directories are created, see the +"`Source Fetching <#source-fetching-dev-environment>`__" section. For +more information on how to create patches and how the build system +processes patches, see the +":ref:`dev-manual/dev-manual-common-tasks:patching code`" +section in the +Yocto Project Development Tasks Manual. You can also see the +":ref:`sdk-manual/sdk-extensible:use \`\`devtool modify\`\` to modify the source of an existing component`" +section in the Yocto Project Application Development and the Extensible +Software Development Kit (SDK) manual and the +":ref:`kernel-dev/kernel-dev-common:using traditional kernel development to patch the kernel`" +section in the Yocto Project Linux Kernel Development Manual. + +.. _configuration-compilation-and-staging-dev-environment: + +Configuration, Compilation, and Staging +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +After source code is patched, BitBake executes tasks that configure and +compile the source code. Once compilation occurs, the files are copied +to a holding area (staged) in preparation for packaging: + +.. image:: figures/configuration-compile-autoreconf.png + :align: center + +This step in the build process consists of the following tasks: + +- :ref:`ref-tasks-prepare_recipe_sysroot`: + This task sets up the two sysroots in + ``${``\ :term:`WORKDIR`\ ``}`` + (i.e. ``recipe-sysroot`` and ``recipe-sysroot-native``) so that + during the packaging phase the sysroots can contain the contents of + the + :ref:`ref-tasks-populate_sysroot` + tasks of the recipes on which the recipe containing the tasks + depends. A sysroot exists for both the target and for the native + binaries, which run on the host system. + +- *do_configure*: This task configures the source by enabling and + disabling any build-time and configuration options for the software + being built. Configurations can come from the recipe itself as well + as from an inherited class. Additionally, the software itself might + configure itself depending on the target for which it is being built. + + The configurations handled by the + :ref:`ref-tasks-configure` task + are specific to configurations for the source code being built by the + recipe. + + If you are using the + :ref:`autotools ` class, + you can add additional configuration options by using the + :term:`EXTRA_OECONF` or + :term:`PACKAGECONFIG_CONFARGS` + variables. For information on how this variable works within that + class, see the + :ref:`autotools ` class + :yocto_git:`here `. + +- *do_compile*: Once a configuration task has been satisfied, + BitBake compiles the source using the + :ref:`ref-tasks-compile` task. + Compilation occurs in the directory pointed to by the + :term:`B` variable. Realize that the + ``B`` directory is, by default, the same as the + :term:`S` directory. + +- *do_install*: After compilation completes, BitBake executes the + :ref:`ref-tasks-install` task. + This task copies files from the ``B`` directory and places them in a + holding area pointed to by the :term:`D` + variable. Packaging occurs later using files from this holding + directory. + +.. _package-splitting-dev-environment: + +Package Splitting +~~~~~~~~~~~~~~~~~ + +After source code is configured, compiled, and staged, the build system +analyzes the results and splits the output into packages: + +.. image:: figures/analysis-for-package-splitting.png + :align: center + +The :ref:`ref-tasks-package` and +:ref:`ref-tasks-packagedata` +tasks combine to analyze the files found in the +:term:`D` directory and split them into +subsets based on available packages and files. Analysis involves the +following as well as other items: splitting out debugging symbols, +looking at shared library dependencies between packages, and looking at +package relationships. + +The ``do_packagedata`` task creates package metadata based on the +analysis such that the build system can generate the final packages. The +:ref:`ref-tasks-populate_sysroot` +task stages (copies) a subset of the files installed by the +:ref:`ref-tasks-install` task into +the appropriate sysroot. Working, staged, and intermediate results of +the analysis and package splitting process use several areas: + +- :term:`PKGD`: The destination + directory (i.e. ``package``) for packages before they are split into + individual packages. + +- :term:`PKGDESTWORK`: A + temporary work area (i.e. ``pkgdata``) used by the ``do_package`` + task to save package metadata. + +- :term:`PKGDEST`: The parent + directory (i.e. ``packages-split``) for packages after they have been + split. + +- :term:`PKGDATA_DIR`: A shared, + global-state directory that holds packaging metadata generated during + the packaging process. The packaging process copies metadata from + ``PKGDESTWORK`` to the ``PKGDATA_DIR`` area where it becomes globally + available. + +- :term:`STAGING_DIR_HOST`: + The path for the sysroot for the system on which a component is built + to run (i.e. ``recipe-sysroot``). + +- :term:`STAGING_DIR_NATIVE`: + The path for the sysroot used when building components for the build + host (i.e. ``recipe-sysroot-native``). + +- :term:`STAGING_DIR_TARGET`: + The path for the sysroot used when a component that is built to + execute on a system and it generates code for yet another machine + (e.g. cross-canadian recipes). + +The :term:`FILES` variable defines the +files that go into each package in +:term:`PACKAGES`. If you want +details on how this is accomplished, you can look at +:yocto_git:`package.bbclass `. + +Depending on the type of packages being created (RPM, DEB, or IPK), the +:ref:`do_package_write_* ` +task creates the actual packages and places them in the Package Feed +area, which is ``${TMPDIR}/deploy``. You can see the "`Package +Feeds <#package-feeds-dev-environment>`__" section for more detail on +that part of the build process. + +.. note:: + + Support for creating feeds directly from the + deploy/\* + directories does not exist. Creating such feeds usually requires some + kind of feed maintenance mechanism that would upload the new packages + into an official package feed (e.g. the Ångström distribution). This + functionality is highly distribution-specific and thus is not + provided out of the box. + +.. _image-generation-dev-environment: + +Image Generation +~~~~~~~~~~~~~~~~ + +Once packages are split and stored in the Package Feeds area, the build +system uses BitBake to generate the root filesystem image: + +.. image:: figures/image-generation.png + :align: center + +The image generation process consists of several stages and depends on +several tasks and variables. The +:ref:`ref-tasks-rootfs` task creates +the root filesystem (file and directory structure) for an image. This +task uses several key variables to help create the list of packages to +actually install: + +- :term:`IMAGE_INSTALL`: Lists + out the base set of packages from which to install from the Package + Feeds area. + +- :term:`PACKAGE_EXCLUDE`: + Specifies packages that should not be installed into the image. + +- :term:`IMAGE_FEATURES`: + Specifies features to include in the image. Most of these features + map to additional packages for installation. + +- :term:`PACKAGE_CLASSES`: + Specifies the package backend (e.g. RPM, DEB, or IPK) to use and + consequently helps determine where to locate packages within the + Package Feeds area. + +- :term:`IMAGE_LINGUAS`: + Determines the language(s) for which additional language support + packages are installed. + +- :term:`PACKAGE_INSTALL`: + The final list of packages passed to the package manager for + installation into the image. + +With :term:`IMAGE_ROOTFS` +pointing to the location of the filesystem under construction and the +``PACKAGE_INSTALL`` variable providing the final list of packages to +install, the root file system is created. + +Package installation is under control of the package manager (e.g. +dnf/rpm, opkg, or apt/dpkg) regardless of whether or not package +management is enabled for the target. At the end of the process, if +package management is not enabled for the target, the package manager's +data files are deleted from the root filesystem. As part of the final +stage of package installation, post installation scripts that are part +of the packages are run. Any scripts that fail to run on the build host +are run on the target when the target system is first booted. If you are +using a +:ref:`read-only root filesystem `, +all the post installation scripts must succeed on the build host during +the package installation phase since the root filesystem on the target +is read-only. + +The final stages of the ``do_rootfs`` task handle post processing. Post +processing includes creation of a manifest file and optimizations. + +The manifest file (``.manifest``) resides in the same directory as the +root filesystem image. This file lists out, line-by-line, the installed +packages. The manifest file is useful for the +:ref:`testimage ` class, +for example, to determine whether or not to run specific tests. See the +:term:`IMAGE_MANIFEST` +variable for additional information. + +Optimizing processes that are run across the image include ``mklibs``, +``prelink``, and any other post-processing commands as defined by the +:term:`ROOTFS_POSTPROCESS_COMMAND` +variable. The ``mklibs`` process optimizes the size of the libraries, +while the ``prelink`` process optimizes the dynamic linking of shared +libraries to reduce start up time of executables. + +After the root filesystem is built, processing begins on the image +through the :ref:`ref-tasks-image` +task. The build system runs any pre-processing commands as defined by +the +:term:`IMAGE_PREPROCESS_COMMAND` +variable. This variable specifies a list of functions to call before the +build system creates the final image output files. + +The build system dynamically creates ``do_image_*`` tasks as needed, +based on the image types specified in the +:term:`IMAGE_FSTYPES` variable. +The process turns everything into an image file or a set of image files +and can compress the root filesystem image to reduce the overall size of +the image. The formats used for the root filesystem depend on the +``IMAGE_FSTYPES`` variable. Compression depends on whether the formats +support compression. + +As an example, a dynamically created task when creating a particular +image type would take the following form: +:: + + do_image_type + +So, if the type +as specified by the ``IMAGE_FSTYPES`` were ``ext4``, the dynamically +generated task would be as follows: +:: + + do_image_ext4 + +The final task involved in image creation is the +:ref:`do_image_complete ` +task. This task completes the image by applying any image post +processing as defined through the +:term:`IMAGE_POSTPROCESS_COMMAND` +variable. The variable specifies a list of functions to call once the +build system has created the final image output files. + +.. note:: + + The entire image generation process is run under + Pseudo. Running under Pseudo ensures that the files in the root filesystem + have correct ownership. + +.. _sdk-generation-dev-environment: + +SDK Generation +~~~~~~~~~~~~~~ + +The OpenEmbedded build system uses BitBake to generate the Software +Development Kit (SDK) installer scripts for both the standard SDK and +the extensible SDK (eSDK): + +.. image:: figures/sdk-generation.png + :align: center + +.. note:: + + For more information on the cross-development toolchain generation, + see the ":ref:`overview-manual/overview-manual-concepts:cross-development toolchain generation`" + section. For information on advantages gained when building a + cross-development toolchain using the do_populate_sdk task, see the + ":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`" section in + the Yocto Project Application Development and the Extensible Software + Development Kit (eSDK) manual. + +Like image generation, the SDK script process consists of several stages +and depends on many variables. The +:ref:`ref-tasks-populate_sdk` +and +:ref:`ref-tasks-populate_sdk_ext` +tasks use these key variables to help create the list of packages to +actually install. For information on the variables listed in the figure, +see the "`Application Development SDK <#sdk-dev-environment>`__" +section. + +The ``do_populate_sdk`` task helps create the standard SDK and handles +two parts: a target part and a host part. The target part is the part +built for the target hardware and includes libraries and headers. The +host part is the part of the SDK that runs on the +:term:`SDKMACHINE`. + +The ``do_populate_sdk_ext`` task helps create the extensible SDK and +handles host and target parts differently than its counter part does for +the standard SDK. For the extensible SDK, the task encapsulates the +build system, which includes everything needed (host and target) for the +SDK. + +Regardless of the type of SDK being constructed, the tasks perform some +cleanup after which a cross-development environment setup script and any +needed configuration files are created. The final output is the +Cross-development toolchain installation script (``.sh`` file), which +includes the environment setup script. + +Stamp Files and the Rerunning of Tasks +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +For each task that completes successfully, BitBake writes a stamp file +into the :term:`STAMPS_DIR` +directory. The beginning of the stamp file's filename is determined by +the :term:`STAMP` variable, and the end +of the name consists of the task's name and current `input +checksum <#overview-checksums>`__. + +.. note:: + + This naming scheme assumes that + BB_SIGNATURE_HANDLER + is "OEBasicHash", which is almost always the case in current + OpenEmbedded. + +To determine if a task needs to be rerun, BitBake checks if a stamp file +with a matching input checksum exists for the task. If such a stamp file +exists, the task's output is assumed to exist and still be valid. If the +file does not exist, the task is rerun. + +.. note:: + + The stamp mechanism is more general than the shared state (sstate) + cache mechanism described in the "`Setscene Tasks and Shared + State <#setscene-tasks-and-shared-state>`__" section. BitBake avoids + rerunning any task that has a valid stamp file, not just tasks that + can be accelerated through the sstate cache. + + However, you should realize that stamp files only serve as a marker + that some work has been done and that these files do not record task + output. The actual task output would usually be somewhere in + :term:`TMPDIR` (e.g. in some + recipe's :term:`WORKDIR`.) What + the sstate cache mechanism adds is a way to cache task output that + can then be shared between build machines. + +Since ``STAMPS_DIR`` is usually a subdirectory of ``TMPDIR``, removing +``TMPDIR`` will also remove ``STAMPS_DIR``, which means tasks will +properly be rerun to repopulate ``TMPDIR``. + +If you want some task to always be considered "out of date", you can +mark it with the :ref:`nostamp ` +varflag. If some other task depends on such a task, then that task will +also always be considered out of date, which might not be what you want. + +For details on how to view information about a task's signature, see the +":ref:`dev-manual/dev-manual-common-tasks:viewing task variable dependencies`" +section in the Yocto Project Development Tasks Manual. + +Setscene Tasks and Shared State +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The description of tasks so far assumes that BitBake needs to build +everything and no available prebuilt objects exist. BitBake does support +skipping tasks if prebuilt objects are available. These objects are +usually made available in the form of a shared state (sstate) cache. + +.. note:: + + For information on variables affecting sstate, see the + :term:`SSTATE_DIR` + and + :term:`SSTATE_MIRRORS` + variables. + +The idea of a setscene task (i.e ``do_``\ taskname\ ``_setscene``) is a +version of the task where instead of building something, BitBake can +skip to the end result and simply place a set of files into specific +locations as needed. In some cases, it makes sense to have a setscene +task variant (e.g. generating package files in the +:ref:`do_package_write_* ` +task). In other cases, it does not make sense (e.g. a +:ref:`ref-tasks-patch` task or a +:ref:`ref-tasks-unpack` task) since +the work involved would be equal to or greater than the underlying task. + +In the build system, the common tasks that have setscene variants are +:ref:`ref-tasks-package`, +``do_package_write_*``, +:ref:`ref-tasks-deploy`, +:ref:`ref-tasks-packagedata`, and +:ref:`ref-tasks-populate_sysroot`. +Notice that these tasks represent most of the tasks whose output is an +end result. + +The build system has knowledge of the relationship between these tasks +and other preceding tasks. For example, if BitBake runs +``do_populate_sysroot_setscene`` for something, it does not make sense +to run any of the ``do_fetch``, ``do_unpack``, ``do_patch``, +``do_configure``, ``do_compile``, and ``do_install`` tasks. However, if +``do_package`` needs to be run, BitBake needs to run those other tasks. + +It becomes more complicated if everything can come from an sstate cache +because some objects are simply not required at all. For example, you do +not need a compiler or native tools, such as quilt, if nothing exists to +compile or patch. If the ``do_package_write_*`` packages are available +from sstate, BitBake does not need the ``do_package`` task data. + +To handle all these complexities, BitBake runs in two phases. The first +is the "setscene" stage. During this stage, BitBake first checks the +sstate cache for any targets it is planning to build. BitBake does a +fast check to see if the object exists rather than a complete download. +If nothing exists, the second phase, which is the setscene stage, +completes and the main build proceeds. + +If objects are found in the sstate cache, the build system works +backwards from the end targets specified by the user. For example, if an +image is being built, the build system first looks for the packages +needed for that image and the tools needed to construct an image. If +those are available, the compiler is not needed. Thus, the compiler is +not even downloaded. If something was found to be unavailable, or the +download or setscene task fails, the build system then tries to install +dependencies, such as the compiler, from the cache. + +The availability of objects in the sstate cache is handled by the +function specified by the +:term:`bitbake:BB_HASHCHECK_FUNCTION` +variable and returns a list of available objects. The function specified +by the +:term:`bitbake:BB_SETSCENE_DEPVALID` +variable is the function that determines whether a given dependency +needs to be followed, and whether for any given relationship the +function needs to be passed. The function returns a True or False value. + +.. _images-dev-environment: + +Images +------ + +The images produced by the build system are compressed forms of the root +filesystem and are ready to boot on a target device. You can see from +the `general workflow figure <#general-workflow-figure>`__ that BitBake +output, in part, consists of images. This section takes a closer look at +this output: + +.. image:: figures/images.png + :align: center + +.. note:: + + For a list of example images that the Yocto Project provides, see the + ":doc:`../ref-manual/ref-images`" chapter in the Yocto Project Reference + Manual. + +The build process writes images out to the :term:`Build Directory` +inside the +``tmp/deploy/images/machine/`` folder as shown in the figure. This +folder contains any files expected to be loaded on the target device. +The :term:`DEPLOY_DIR` variable +points to the ``deploy`` directory, while the +:term:`DEPLOY_DIR_IMAGE` +variable points to the appropriate directory containing images for the +current configuration. + +- kernel-image: A kernel binary file. The + :term:`KERNEL_IMAGETYPE` + variable determines the naming scheme for the kernel image file. + Depending on this variable, the file could begin with a variety of + naming strings. The ``deploy/images/``\ machine directory can contain + multiple image files for the machine. + +- root-filesystem-image: Root filesystems for the target device (e.g. + ``*.ext3`` or ``*.bz2`` files). The + :term:`IMAGE_FSTYPES` + variable determines the root filesystem image type. The + ``deploy/images/``\ machine directory can contain multiple root + filesystems for the machine. + +- kernel-modules: Tarballs that contain all the modules built for the + kernel. Kernel module tarballs exist for legacy purposes and can be + suppressed by setting the + :term:`MODULE_TARBALL_DEPLOY` + variable to "0". The ``deploy/images/``\ machine directory can + contain multiple kernel module tarballs for the machine. + +- bootloaders: If applicable to the target machine, bootloaders + supporting the image. The ``deploy/images/``\ machine directory can + contain multiple bootloaders for the machine. + +- symlinks: The ``deploy/images/``\ machine folder contains a symbolic + link that points to the most recently built file for each machine. + These links might be useful for external scripts that need to obtain + the latest version of each file. + +.. _sdk-dev-environment: + +Application Development SDK +--------------------------- + +In the `general workflow figure <#general-workflow-figure>`__, the +output labeled "Application Development SDK" represents an SDK. The SDK +generation process differs depending on whether you build an extensible +SDK (e.g. ``bitbake -c populate_sdk_ext`` imagename) or a standard SDK +(e.g. ``bitbake -c populate_sdk`` imagename). This section takes a +closer look at this output: + +.. image:: figures/sdk.png + :align: center + +The specific form of this output is a set of files that includes a +self-extracting SDK installer (``*.sh``), host and target manifest +files, and files used for SDK testing. When the SDK installer file is +run, it installs the SDK. The SDK consists of a cross-development +toolchain, a set of libraries and headers, and an SDK environment setup +script. Running this installer essentially sets up your +cross-development environment. You can think of the cross-toolchain as +the "host" part because it runs on the SDK machine. You can think of the +libraries and headers as the "target" part because they are built for +the target hardware. The environment setup script is added so that you +can initialize the environment before using the tools. + +.. note:: + + - The Yocto Project supports several methods by which you can set up + this cross-development environment. These methods include + downloading pre-built SDK installers or building and installing + your own SDK installer. + + - For background information on cross-development toolchains in the + Yocto Project development environment, see the "`Cross-Development + Toolchain Generation <#cross-development-toolchain-generation>`__" + section. + + - For information on setting up a cross-development environment, see + the :doc:`../sdk-manual/sdk-manual` manual. + +All the output files for an SDK are written to the ``deploy/sdk`` folder +inside the :term:`Build Directory` as +shown in the previous figure. Depending on the type of SDK, several +variables exist that help configure these files. The following list +shows the variables associated with an extensible SDK: + +- :term:`DEPLOY_DIR`: Points to + the ``deploy`` directory. + +- :term:`SDK_EXT_TYPE`: + Controls whether or not shared state artifacts are copied into the + extensible SDK. By default, all required shared state artifacts are + copied into the SDK. + +- :term:`SDK_INCLUDE_PKGDATA`: + Specifies whether or not packagedata is included in the extensible + SDK for all recipes in the "world" target. + +- :term:`SDK_INCLUDE_TOOLCHAIN`: + Specifies whether or not the toolchain is included when building the + extensible SDK. + +- :term:`SDK_LOCAL_CONF_WHITELIST`: + A list of variables allowed through from the build system + configuration into the extensible SDK configuration. + +- :term:`SDK_LOCAL_CONF_BLACKLIST`: + A list of variables not allowed through from the build system + configuration into the extensible SDK configuration. + +- :term:`SDK_INHERIT_BLACKLIST`: + A list of classes to remove from the + :term:`INHERIT` value globally + within the extensible SDK configuration. + +This next list, shows the variables associated with a standard SDK: + +- :term:`DEPLOY_DIR`: Points to + the ``deploy`` directory. + +- :term:`SDKMACHINE`: Specifies + the architecture of the machine on which the cross-development tools + are run to create packages for the target hardware. + +- :term:`SDKIMAGE_FEATURES`: + Lists the features to include in the "target" part of the SDK. + +- :term:`TOOLCHAIN_HOST_TASK`: + Lists packages that make up the host part of the SDK (i.e. the part + that runs on the ``SDKMACHINE``). When you use + ``bitbake -c populate_sdk imagename`` to create the SDK, a set of + default packages apply. This variable allows you to add more + packages. + +- :term:`TOOLCHAIN_TARGET_TASK`: + Lists packages that make up the target part of the SDK (i.e. the part + built for the target hardware). + +- :term:`SDKPATH`: Defines the + default SDK installation path offered by the installation script. + +- :term:`SDK_HOST_MANIFEST`: + Lists all the installed packages that make up the host part of the + SDK. This variable also plays a minor role for extensible SDK + development as well. However, it is mainly used for the standard SDK. + +- :term:`SDK_TARGET_MANIFEST`: + Lists all the installed packages that make up the target part of the + SDK. This variable also plays a minor role for extensible SDK + development as well. However, it is mainly used for the standard SDK. + +Cross-Development Toolchain Generation +====================================== + +The Yocto Project does most of the work for you when it comes to +creating :ref:`sdk-manual/sdk-intro:the cross-development toolchain`. This +section provides some technical background on how cross-development +toolchains are created and used. For more information on toolchains, you +can also see the :doc:`../sdk-manual/sdk-manual` manual. + +In the Yocto Project development environment, cross-development +toolchains are used to build images and applications that run on the +target hardware. With just a few commands, the OpenEmbedded build system +creates these necessary toolchains for you. + +The following figure shows a high-level build environment regarding +toolchain construction and use. + +.. image:: figures/cross-development-toolchains.png + :align: center + +Most of the work occurs on the Build Host. This is the machine used to +build images and generally work within the the Yocto Project +environment. When you run +:term:`BitBake` to create an image, the +OpenEmbedded build system uses the host ``gcc`` compiler to bootstrap a +cross-compiler named ``gcc-cross``. The ``gcc-cross`` compiler is what +BitBake uses to compile source files when creating the target image. You +can think of ``gcc-cross`` simply as an automatically generated +cross-compiler that is used internally within BitBake only. + +.. note:: + + The extensible SDK does not use + gcc-cross-canadian + since this SDK ships a copy of the OpenEmbedded build system and the + sysroot within it contains + gcc-cross + . + +The chain of events that occurs when ``gcc-cross`` is bootstrapped is as +follows: +:: + + gcc -> binutils-cross -> gcc-cross-initial -> linux-libc-headers -> glibc-initial -> glibc -> gcc-cross -> gcc-runtime + +- ``gcc``: The build host's GNU Compiler Collection (GCC). + +- ``binutils-cross``: The bare minimum binary utilities needed in order + to run the ``gcc-cross-initial`` phase of the bootstrap operation. + +- ``gcc-cross-initial``: An early stage of the bootstrap process for + creating the cross-compiler. This stage builds enough of the + ``gcc-cross``, the C library, and other pieces needed to finish + building the final cross-compiler in later stages. This tool is a + "native" package (i.e. it is designed to run on the build host). + +- ``linux-libc-headers``: Headers needed for the cross-compiler. + +- ``glibc-initial``: An initial version of the Embedded GNU C Library + (GLIBC) needed to bootstrap ``glibc``. + +- ``glibc``: The GNU C Library. + +- ``gcc-cross``: The final stage of the bootstrap process for the + cross-compiler. This stage results in the actual cross-compiler that + BitBake uses when it builds an image for a targeted device. + + .. note:: + + If you are replacing this cross compiler toolchain with a custom + version, you must replace + gcc-cross + . + + This tool is also a "native" package (i.e. it is designed to run on + the build host). + +- ``gcc-runtime``: Runtime libraries resulting from the toolchain + bootstrapping process. This tool produces a binary that consists of + the runtime libraries need for the targeted device. + +You can use the OpenEmbedded build system to build an installer for the +relocatable SDK used to develop applications. When you run the +installer, it installs the toolchain, which contains the development +tools (e.g., ``gcc-cross-canadian``, ``binutils-cross-canadian``, and +other ``nativesdk-*`` tools), which are tools native to the SDK (i.e. +native to :term:`SDK_ARCH`), you +need to cross-compile and test your software. The figure shows the +commands you use to easily build out this toolchain. This +cross-development toolchain is built to execute on the +:term:`SDKMACHINE`, which might or +might not be the same machine as the Build Host. + +.. note:: + + If your target architecture is supported by the Yocto Project, you + can take advantage of pre-built images that ship with the Yocto + Project and already contain cross-development toolchain installers. + +Here is the bootstrap process for the relocatable toolchain: +:: + + gcc -> binutils-crosssdk -> gcc-crosssdk-initial -> linux-libc-headers -> glibc-initial -> nativesdk-glibc -> gcc-crosssdk -> gcc-cross-canadian + +- ``gcc``: The build host's GNU Compiler Collection (GCC). + +- ``binutils-crosssdk``: The bare minimum binary utilities needed in + order to run the ``gcc-crosssdk-initial`` phase of the bootstrap + operation. + +- ``gcc-crosssdk-initial``: An early stage of the bootstrap process for + creating the cross-compiler. This stage builds enough of the + ``gcc-crosssdk`` and supporting pieces so that the final stage of the + bootstrap process can produce the finished cross-compiler. This tool + is a "native" binary that runs on the build host. + +- ``linux-libc-headers``: Headers needed for the cross-compiler. + +- ``glibc-initial``: An initial version of the Embedded GLIBC needed to + bootstrap ``nativesdk-glibc``. + +- ``nativesdk-glibc``: The Embedded GLIBC needed to bootstrap the + ``gcc-crosssdk``. + +- ``gcc-crosssdk``: The final stage of the bootstrap process for the + relocatable cross-compiler. The ``gcc-crosssdk`` is a transitory + compiler and never leaves the build host. Its purpose is to help in + the bootstrap process to create the eventual ``gcc-cross-canadian`` + compiler, which is relocatable. This tool is also a "native" package + (i.e. it is designed to run on the build host). + +- ``gcc-cross-canadian``: The final relocatable cross-compiler. When + run on the :term:`SDKMACHINE`, + this tool produces executable code that runs on the target device. + Only one cross-canadian compiler is produced per architecture since + they can be targeted at different processor optimizations using + configurations passed to the compiler through the compile commands. + This circumvents the need for multiple compilers and thus reduces the + size of the toolchains. + +.. note:: + + For information on advantages gained when building a + cross-development toolchain installer, see the + ":ref:`sdk-manual/sdk-appendix-obtain:building an sdk installer`" appendix + in the Yocto Project Application Development and the + Extensible Software Development Kit (eSDK) manual. + +Shared State Cache +================== + +By design, the OpenEmbedded build system builds everything from scratch +unless :term:`BitBake` can determine +that parts do not need to be rebuilt. Fundamentally, building from +scratch is attractive as it means all parts are built fresh and no +possibility of stale data exists that can cause problems. When +developers hit problems, they typically default back to building from +scratch so they have a know state from the start. + +Building an image from scratch is both an advantage and a disadvantage +to the process. As mentioned in the previous paragraph, building from +scratch ensures that everything is current and starts from a known +state. However, building from scratch also takes much longer as it +generally means rebuilding things that do not necessarily need to be +rebuilt. + +The Yocto Project implements shared state code that supports incremental +builds. The implementation of the shared state code answers the +following questions that were fundamental roadblocks within the +OpenEmbedded incremental build support system: + +- What pieces of the system have changed and what pieces have not + changed? + +- How are changed pieces of software removed and replaced? + +- How are pre-built components that do not need to be rebuilt from + scratch used when they are available? + +For the first question, the build system detects changes in the "inputs" +to a given task by creating a checksum (or signature) of the task's +inputs. If the checksum changes, the system assumes the inputs have +changed and the task needs to be rerun. For the second question, the +shared state (sstate) code tracks which tasks add which output to the +build process. This means the output from a given task can be removed, +upgraded or otherwise manipulated. The third question is partly +addressed by the solution for the second question assuming the build +system can fetch the sstate objects from remote locations and install +them if they are deemed to be valid. + +.. note:: + + - The build system does not maintain + :term:`PR` information as part of + the shared state packages. Consequently, considerations exist that + affect maintaining shared state feeds. For information on how the + build system works with packages and can track incrementing ``PR`` + information, see the ":ref:`dev-manual/dev-manual-common-tasks:automatically incrementing a package version number`" + section in the Yocto Project Development Tasks Manual. + + - The code in the build system that supports incremental builds is + not simple code. For techniques that help you work around issues + related to shared state code, see the + ":ref:`dev-manual/dev-manual-common-tasks:viewing metadata used to create the input signature of a shared state task`" + and + ":ref:`dev-manual/dev-manual-common-tasks:invalidating shared state to force a task to run`" + sections both in the Yocto Project Development Tasks Manual. + +The rest of this section goes into detail about the overall incremental +build architecture, the checksums (signatures), and shared state. + +.. _concepts-overall-architecture: + +Overall Architecture +-------------------- + +When determining what parts of the system need to be built, BitBake +works on a per-task basis rather than a per-recipe basis. You might +wonder why using a per-task basis is preferred over a per-recipe basis. +To help explain, consider having the IPK packaging backend enabled and +then switching to DEB. In this case, the +:ref:`ref-tasks-install` and +:ref:`ref-tasks-package` task outputs +are still valid. However, with a per-recipe approach, the build would +not include the ``.deb`` files. Consequently, you would have to +invalidate the whole build and rerun it. Rerunning everything is not the +best solution. Also, in this case, the core must be "taught" much about +specific tasks. This methodology does not scale well and does not allow +users to easily add new tasks in layers or as external recipes without +touching the packaged-staging core. + +.. _overview-checksums: + +Checksums (Signatures) +---------------------- + +The shared state code uses a checksum, which is a unique signature of a +task's inputs, to determine if a task needs to be run again. Because it +is a change in a task's inputs that triggers a rerun, the process needs +to detect all the inputs to a given task. For shell tasks, this turns +out to be fairly easy because the build process generates a "run" shell +script for each task and it is possible to create a checksum that gives +you a good idea of when the task's data changes. + +To complicate the problem, there are things that should not be included +in the checksum. First, there is the actual specific build path of a +given task - the :term:`WORKDIR`. It +does not matter if the work directory changes because it should not +affect the output for target packages. Also, the build process has the +objective of making native or cross packages relocatable. + +.. note:: + + Both native and cross packages run on the + build host. However, cross packages generate output for the target + architecture. + +The checksum therefore needs to exclude ``WORKDIR``. The simplistic +approach for excluding the work directory is to set ``WORKDIR`` to some +fixed value and create the checksum for the "run" script. + +Another problem results from the "run" scripts containing functions that +might or might not get called. The incremental build solution contains +code that figures out dependencies between shell functions. This code is +used to prune the "run" scripts down to the minimum set, thereby +alleviating this problem and making the "run" scripts much more readable +as a bonus. + +So far, solutions for shell scripts exist. What about Python tasks? The +same approach applies even though these tasks are more difficult. The +process needs to figure out what variables a Python function accesses +and what functions it calls. Again, the incremental build solution +contains code that first figures out the variable and function +dependencies, and then creates a checksum for the data used as the input +to the task. + +Like the ``WORKDIR`` case, situations exist where dependencies should be +ignored. For these situations, you can instruct the build process to +ignore a dependency by using a line like the following: +:: + + PACKAGE_ARCHS[vardepsexclude] = "MACHINE" + +This example ensures that the :term:`PACKAGE_ARCHS` variable +does not depend on the value of :term:`MACHINE`, even if it does +reference it. + +Equally, there are cases where you need to add dependencies BitBake is +not able to find. You can accomplish this by using a line like the +following: +:: + + PACKAGE_ARCHS[vardeps] = "MACHINE" + +This example explicitly +adds the ``MACHINE`` variable as a dependency for ``PACKAGE_ARCHS``. + +As an example, consider a case with in-line Python where BitBake is not +able to figure out dependencies. When running in debug mode (i.e. using +``-DDD``), BitBake produces output when it discovers something for which +it cannot figure out dependencies. The Yocto Project team has currently +not managed to cover those dependencies in detail and is aware of the +need to fix this situation. + +Thus far, this section has limited discussion to the direct inputs into +a task. Information based on direct inputs is referred to as the +"basehash" in the code. However, the question of a task's indirect +inputs still exits - items already built and present in the +:term:`Build Directory`. The checksum (or +signature) for a particular task needs to add the hashes of all the +tasks on which the particular task depends. Choosing which dependencies +to add is a policy decision. However, the effect is to generate a master +checksum that combines the basehash and the hashes of the task's +dependencies. + +At the code level, a variety of ways exist by which both the basehash +and the dependent task hashes can be influenced. Within the BitBake +configuration file, you can give BitBake some extra information to help +it construct the basehash. The following statement effectively results +in a list of global variable dependency excludes (i.e. variables never +included in any checksum): +:: + + BB_HASHBASE_WHITELIST ?= "TMPDIR FILE PATH PWD BB_TASKHASH BBPATH DL_DIR \\ + SSTATE_DIR THISDIR FILESEXTRAPATHS FILE_DIRNAME HOME LOGNAME SHELL TERM \\ + USER FILESPATH STAGING_DIR_HOST STAGING_DIR_TARGET COREBASE PRSERV_HOST \\ + PRSERV_DUMPDIR PRSERV_DUMPFILE PRSERV_LOCKDOWN PARALLEL_MAKE \\ + CCACHE_DIR EXTERNAL_TOOLCHAIN CCACHE CCACHE_DISABLE LICENSE_PATH SDKPKGSUFFIX" + +The +previous example excludes +:term:`WORKDIR` since that variable +is actually constructed as a path within +:term:`TMPDIR`, which is on the +whitelist. + +The rules for deciding which hashes of dependent tasks to include +through dependency chains are more complex and are generally +accomplished with a Python function. The code in +``meta/lib/oe/sstatesig.py`` shows two examples of this and also +illustrates how you can insert your own policy into the system if so +desired. This file defines the two basic signature generators +:term:`OpenEmbedded-Core (OE-Core)` uses: "OEBasic" and +"OEBasicHash". By default, a dummy "noop" signature handler is enabled +in BitBake. This means that behavior is unchanged from previous +versions. OE-Core uses the "OEBasicHash" signature handler by default +through this setting in the ``bitbake.conf`` file: +:: + + BB_SIGNATURE_HANDLER ?= "OEBasicHash" + +The "OEBasicHash" ``BB_SIGNATURE_HANDLER`` is the same +as the "OEBasic" version but adds the task hash to the `stamp +files <#stamp-files-and-the-rerunning-of-tasks>`__. This results in any +metadata change that changes the task hash, automatically causing the +task to be run again. This removes the need to bump +:term:`PR` values, and changes to metadata +automatically ripple across the build. + +It is also worth noting that the end result of these signature +generators is to make some dependency and hash information available to +the build. This information includes: + +- ``BB_BASEHASH_task-``\ taskname: The base hashes for each task in the + recipe. + +- ``BB_BASEHASH_``\ filename\ ``:``\ taskname: The base hashes for each + dependent task. + +- ``BBHASHDEPS_``\ filename\ ``:``\ taskname: The task dependencies for + each task. + +- ``BB_TASKHASH``: The hash of the currently running task. + +Shared State +------------ + +Checksums and dependencies, as discussed in the previous section, solve +half the problem of supporting a shared state. The other half of the +problem is being able to use checksum information during the build and +being able to reuse or rebuild specific components. + +The :ref:`sstate ` class is a +relatively generic implementation of how to "capture" a snapshot of a +given task. The idea is that the build process does not care about the +source of a task's output. Output could be freshly built or it could be +downloaded and unpacked from somewhere. In other words, the build +process does not need to worry about its origin. + +Two types of output exist. One type is just about creating a directory +in :term:`WORKDIR`. A good example is +the output of either +:ref:`ref-tasks-install` or +:ref:`ref-tasks-package`. The other +type of output occurs when a set of data is merged into a shared +directory tree such as the sysroot. + +The Yocto Project team has tried to keep the details of the +implementation hidden in ``sstate`` class. From a user's perspective, +adding shared state wrapping to a task is as simple as this +:ref:`ref-tasks-deploy` example taken +from the :ref:`deploy ` class: +:: + + DEPLOYDIR = "${WORKDIR}/deploy-${PN}" + SSTATETASKS += "do_deploy" + do_deploy[sstate-inputdirs] = "${DEPLOYDIR}" + do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}" + + python do_deploy_setscene () { + sstate_setscene(d) + } + addtask do_deploy_setscene + do_deploy[dirs] = "${DEPLOYDIR} ${B}" + do_deploy[stamp-extra-info] = "${MACHINE_ARCH}" + +The following list explains the previous example: + +- Adding "do_deploy" to ``SSTATETASKS`` adds some required + sstate-related processing, which is implemented in the + :ref:`sstate ` class, to + before and after the + :ref:`ref-tasks-deploy` task. + +- The ``do_deploy[sstate-inputdirs] = "${DEPLOYDIR}"`` declares that + ``do_deploy`` places its output in ``${DEPLOYDIR}`` when run normally + (i.e. when not using the sstate cache). This output becomes the input + to the shared state cache. + +- The ``do_deploy[sstate-outputdirs] = "${DEPLOY_DIR_IMAGE}"`` line + causes the contents of the shared state cache to be copied to + ``${DEPLOY_DIR_IMAGE}``. + + .. note:: + + If ``do_deploy`` is not already in the shared state cache or if its input + checksum (signature) has changed from when the output was cached, the task + runs to populate the shared state cache, after which the contents of the + shared state cache is copied to ${:term:`DEPLOY_DIR_IMAGE`}. If + ``do_deploy`` is in the shared state cache and its signature indicates + that the cached output is still valid (i.e. if no relevant task inputs + have changed), then the contents of the shared state cache copies + directly to ${``DEPLOY_DIR_IMAGE``} by the ``do_deploy_setscene`` task + instead, skipping the ``do_deploy`` task. + +- The following task definition is glue logic needed to make the + previous settings effective: + :: + + python do_deploy_setscene () { + sstate_setscene(d) + } + addtask do_deploy_setscene + + ``sstate_setscene()`` takes the flags above as input and accelerates the ``do_deploy`` task + through the shared state cache if possible. If the task was + accelerated, ``sstate_setscene()`` returns True. Otherwise, it + returns False, and the normal ``do_deploy`` task runs. For more + information, see the ":ref:`setscene `" + section in the BitBake User Manual. + +- The ``do_deploy[dirs] = "${DEPLOYDIR} ${B}"`` line creates + ``${DEPLOYDIR}`` and ``${B}`` before the ``do_deploy`` task runs, and + also sets the current working directory of ``do_deploy`` to ``${B}``. + For more information, see the ":ref:`bitbake:bitbake-user-manual/bitbake-user-manual-metadata:variable flags`" + section in the BitBake + User Manual. + + .. note:: + + In cases where ``sstate-inputdirs`` and ``sstate-outputdirs`` would be + the same, you can use ``sstate-plaindirs``. For example, to preserve the + ${:term:`PKGD`} and ${:term:`PKGDEST`} output from the ``do_package`` + task, use the following: + :: + + do_package[sstate-plaindirs] = "${PKGD} ${PKGDEST}" + + +- The ``do_deploy[stamp-extra-info] = "${MACHINE_ARCH}"`` line appends + extra metadata to the `stamp + file <#stamp-files-and-the-rerunning-of-tasks>`__. In this case, the + metadata makes the task specific to a machine's architecture. See + ":ref:`bitbake:ref-bitbake-tasklist`" + section in the BitBake User Manual for more information on the + ``stamp-extra-info`` flag. + +- ``sstate-inputdirs`` and ``sstate-outputdirs`` can also be used with + multiple directories. For example, the following declares + ``PKGDESTWORK`` and ``SHLIBWORK`` as shared state input directories, + which populates the shared state cache, and ``PKGDATA_DIR`` and + ``SHLIBSDIR`` as the corresponding shared state output directories: + :: + + do_package[sstate-inputdirs] = "${PKGDESTWORK} ${SHLIBSWORKDIR}" + do_package[sstate-outputdirs] = "${PKGDATA_DIR} ${SHLIBSDIR}" + +- These methods also include the ability to take a lockfile when + manipulating shared state directory structures, for cases where file + additions or removals are sensitive: + :: + + do_package[sstate-lockfile] = "${PACKAGELOCK}" + +Behind the scenes, the shared state code works by looking in +:term:`SSTATE_DIR` and +:term:`SSTATE_MIRRORS` for +shared state files. Here is an example: +:: + + SSTATE_MIRRORS ?= "\ + file://.\* http://someserver.tld/share/sstate/PATH;downloadfilename=PATH \n \ + file://.\* file:///some/local/dir/sstate/PATH" + +.. note:: + + The shared state directory (``SSTATE_DIR``) is organized into two-character + subdirectories, where the subdirectory names are based on the first two + characters of the hash. + If the shared state directory structure for a mirror has the same structure + as ``SSTATE_DIR``, you must specify "PATH" as part of the URI to enable the build + system to map to the appropriate subdirectory. + +The shared state package validity can be detected just by looking at the +filename since the filename contains the task checksum (or signature) as +described earlier in this section. If a valid shared state package is +found, the build process downloads it and uses it to accelerate the +task. + +The build processes use the ``*_setscene`` tasks for the task +acceleration phase. BitBake goes through this phase before the main +execution code and tries to accelerate any tasks for which it can find +shared state packages. If a shared state package for a task is +available, the shared state package is used. This means the task and any +tasks on which it is dependent are not executed. + +As a real world example, the aim is when building an IPK-based image, +only the +:ref:`ref-tasks-package_write_ipk` +tasks would have their shared state packages fetched and extracted. +Since the sysroot is not used, it would never get extracted. This is +another reason why a task-based approach is preferred over a +recipe-based approach, which would have to install the output from every +task. + +Automatically Added Runtime Dependencies +======================================== + +The OpenEmbedded build system automatically adds common types of runtime +dependencies between packages, which means that you do not need to +explicitly declare the packages using +:term:`RDEPENDS`. Three automatic +mechanisms exist (``shlibdeps``, ``pcdeps``, and ``depchains``) that +handle shared libraries, package configuration (pkg-config) modules, and +``-dev`` and ``-dbg`` packages, respectively. For other types of runtime +dependencies, you must manually declare the dependencies. + +- ``shlibdeps``: During the + :ref:`ref-tasks-package` task of + each recipe, all shared libraries installed by the recipe are + located. For each shared library, the package that contains the + shared library is registered as providing the shared library. More + specifically, the package is registered as providing the + `soname `__ of the library. The + resulting shared-library-to-package mapping is saved globally in + :term:`PKGDATA_DIR` by the + :ref:`ref-tasks-packagedata` + task. + + Simultaneously, all executables and shared libraries installed by the + recipe are inspected to see what shared libraries they link against. + For each shared library dependency that is found, ``PKGDATA_DIR`` is + queried to see if some package (likely from a different recipe) + contains the shared library. If such a package is found, a runtime + dependency is added from the package that depends on the shared + library to the package that contains the library. + + The automatically added runtime dependency also includes a version + restriction. This version restriction specifies that at least the + current version of the package that provides the shared library must + be used, as if "package (>= version)" had been added to ``RDEPENDS``. + This forces an upgrade of the package containing the shared library + when installing the package that depends on the library, if needed. + + If you want to avoid a package being registered as providing a + particular shared library (e.g. because the library is for internal + use only), then add the library to + :term:`PRIVATE_LIBS` inside + the package's recipe. + +- ``pcdeps``: During the ``do_package`` task of each recipe, all + pkg-config modules (``*.pc`` files) installed by the recipe are + located. For each module, the package that contains the module is + registered as providing the module. The resulting module-to-package + mapping is saved globally in ``PKGDATA_DIR`` by the + ``do_packagedata`` task. + + Simultaneously, all pkg-config modules installed by the recipe are + inspected to see what other pkg-config modules they depend on. A + module is seen as depending on another module if it contains a + "Requires:" line that specifies the other module. For each module + dependency, ``PKGDATA_DIR`` is queried to see if some package + contains the module. If such a package is found, a runtime dependency + is added from the package that depends on the module to the package + that contains the module. + + .. note:: + + The + pcdeps + mechanism most often infers dependencies between + -dev + packages. + +- ``depchains``: If a package ``foo`` depends on a package ``bar``, + then ``foo-dev`` and ``foo-dbg`` are also made to depend on + ``bar-dev`` and ``bar-dbg``, respectively. Taking the ``-dev`` + packages as an example, the ``bar-dev`` package might provide headers + and shared library symlinks needed by ``foo-dev``, which shows the + need for a dependency between the packages. + + The dependencies added by ``depchains`` are in the form of + :term:`RRECOMMENDS`. + + .. note:: + + By default, ``foo-dev`` also has an ``RDEPENDS``-style dependency on + ``foo``, because the default value of ``RDEPENDS_${PN}-dev`` (set in + bitbake.conf) includes "${PN}". + + To ensure that the dependency chain is never broken, ``-dev`` and + ``-dbg`` packages are always generated by default, even if the + packages turn out to be empty. See the + :term:`ALLOW_EMPTY` variable + for more information. + +The ``do_package`` task depends on the ``do_packagedata`` task of each +recipe in :term:`DEPENDS` through use +of a ``[``\ :ref:`deptask `\ ``]`` +declaration, which guarantees that the required +shared-library/module-to-package mapping information will be available +when needed as long as ``DEPENDS`` has been correctly set. + +Fakeroot and Pseudo +=================== + +Some tasks are easier to implement when allowed to perform certain +operations that are normally reserved for the root user (e.g. +:ref:`ref-tasks-install`, +:ref:`do_package_write* `, +:ref:`ref-tasks-rootfs`, and +:ref:`do_image* `). For example, +the ``do_install`` task benefits from being able to set the UID and GID +of installed files to arbitrary values. + +One approach to allowing tasks to perform root-only operations would be +to require :term:`BitBake` to run as +root. However, this method is cumbersome and has security issues. The +approach that is actually used is to run tasks that benefit from root +privileges in a "fake" root environment. Within this environment, the +task and its child processes believe that they are running as the root +user, and see an internally consistent view of the filesystem. As long +as generating the final output (e.g. a package or an image) does not +require root privileges, the fact that some earlier steps ran in a fake +root environment does not cause problems. + +The capability to run tasks in a fake root environment is known as +"`fakeroot `__", which is derived from +the BitBake keyword/variable flag that requests a fake root environment +for a task. + +In the :term:`OpenEmbedded Build System`, +the program that +implements fakeroot is known as +`Pseudo `__. Pseudo +overrides system calls by using the environment variable ``LD_PRELOAD``, +which results in the illusion of running as root. To keep track of +"fake" file ownership and permissions resulting from operations that +require root permissions, Pseudo uses an SQLite 3 database. This +database is stored in +``${``\ :term:`WORKDIR`\ ``}/pseudo/files.db`` +for individual recipes. Storing the database in a file as opposed to in +memory gives persistence between tasks and builds, which is not +accomplished using fakeroot. + +.. note:: + + If you add your own task that manipulates the same files or + directories as a fakeroot task, then that task also needs to run + under fakeroot. Otherwise, the task cannot run root-only operations, + and cannot see the fake file ownership and permissions set by the + other task. You need to also add a dependency on + virtual/fakeroot-native:do_populate_sysroot + , giving the following: + :: + + fakeroot do_mytask () { + ... + } + do_mytask[depends] += "virtual/fakeroot-native:do_populate_sysroot" + + +For more information, see the +:term:`FAKEROOT* ` variables in the +BitBake User Manual. You can also reference the "`Why Not +Fakeroot? `__" +article for background information on Fakeroot and Pseudo. -- cgit v1.2.3