Build internals
To build a package with pmbootstrap, you will only need the command pmbootstrap build hello-world. Optionally with --force to build even if the package was already built, and with --arch=armhf to build for another architecture, replace armhf accordingly. This wiki page lists some more information about what is going on in the background.
initramfs
The initramfs shows the boot splash images, and allows the root partition to be unlocked (currently via telnet). You can add a hook to inspect the initramfs running on the device, as described in Inspecting the initramfs.
To rebuild the initramfs, run mkinitfs inside the chroot with the right parameters (or - much easier - pmbootstrap initfs build). This gets done automatically, whenever a new kernel gets installed, or when the postmarketos-mkinitfs package gets installed the first time.
pmbootstrap vs. abuild
pmbootstrap wraps around abuild (Alpine's official program to build apks), but it does a few things different than abuild (which internally often calls apk):
pmbootstrapcan cross-compile out of the box, utilizing different chroots as needed (see below for details)pmbootstrapdoes dependency parsing on its own (so it works across theaportsfolder and the binary repository and can detect across chroots when a package is outdated and explicitly install them).pmbootstrapdoes not honor operators in dependencies, such as:<,>,=,!. These simply get ignored (!packages don't count as dependencies). This may lead to errors, if it does please report them. However, since we're callingapkto install the packages, it does the real dependency checking and so far it's working well enough.pmbootstrapparsesAPKINDEXandAPKBUILDfiles on its own.APKINDEXparsing is considered to be pretty good (because the format is dead simple!)APKBUILDparsing would require a shell to be done perfectly (which would in turn kill performance). The way it is implemented right now, is that the variables we care about are hardcoded inside thepbm/config/__config__.pyor if not possible otherwise directly inpmb/parse/apkbuild.py. That is really fast and works for all packages we care about. If it breaks somewhere, it should be easy to patch.pmbootstrapdoes not remove build dependencies after a build is done (except when using--strict). This is for performance reasons - if you want a clean start, runpmbootstrap zap.pmbootstraphas a hack right now, thatgzipalways uses weak compression (also for speed)
Cross-compile types
This section has moved to: https://docs.postmarketos.org/pmbootstrap/cross_compiling.html
Caches
pmbootstrap uses various caches. They can all be found inside the work folder, and start with cache_. All cache folders get mounted to the appropriate chroots, depending on $ARCH. They are shared among the chroots, when it makes sense (e.g. cache_distfiles).
cache_apk_$ARCH: APK files from binary repositories (see also: Local APK cache)cache_ccache_$ARCH: ccache: Whenever you compile something withpmbootstrap, the output gets cached in this folder (depending on the architecture). When you compile the same code for the second time, the cached output gets used, thus saving you a lot of time (think of re-compiling kernels, because you want to test another kernel config option etc.)cache_distfiles: Whenever you build a package,abuild(which pmbootstrap wraps) will download the source files to thedistfilescache (and skip these downloads, when they already exist). The exact file name can be controlled inside the APKBUILD (more info).cache_git:pmbootstrapcan download git repositories. This gets used inpmbootstrap aportgen, which copies a package (aka. aport) from Alpine Linux and customizes it (for example:gcc-armhf), so we inherit all patches and changes automatically, without much maintenance work. The git repos get stored inside this folder.cache_http: This stores files, that get downloaded withpmb.helpers.http.download(), so they don't need to be downloaded again every time. Currently, this gets used for the initial download of Alpine Linux' main repositoriesAPKINDEX.tar.gzand apk-tools-static (which is a static build of theapkpackage manager, used to set up the chroot).
Why noarch packages are built for each architecture
For a noarch package, we could in theory compile it once and then create symlinks to all arches pointing to the package where we have created it. And previous versions of pmbootstrap used to do that. But that makes dependency parsing hard.
For example: device packages are always noarch, so in theory you could compile the device package for your armhf device in x86_64, and then symlink it to the armhf package folder. But it would still depend on the kernel, which is armhf only for that device (assuming it is not mainlined, like most devices are right now). So it would not make sense to install it in x86_64 anyway, and if you would want to build it, you could only really do it in armhf anyway, because that's where the kernel is available.
So to simplify it, it is handled like in Alpine now; noarch packages just get built for each arch independently.
pmbootstrap specific APKBUILD options
For various reasons, we have added support for the following pmbootstrap specific values in APKBUILD options.
!pmb:crossdirect: do not use the crossdirect method (!1922). pmbootstrap will just build completely in qemu (slow).!pmb:kconfigcheck: for linux-* packages only. When set, the given linux package does not fail "pmbootstrap kconfig check" (!1753).pmb:cross-native: build the package using the "cross-native" cross compilation method !1920pmb:cross-native2: build the package using the improved "cross-native2" cross compilation method !2474pmb:gpu-accel: used for UI specific packages to define GPU acceleration requirement !2043pmb:strict: always build the package in strict mode, even if --strict is not passed to "pmbootstrap build" (!1771).