bitbake for XCP-ng

This is a set of Bitbake classes and recipes to build packages that make up a XCP-ng distribution, on top of an upstream distribution (namely AlmaLinux 10 + EPEL). The intention is to build XCP-ng 9.0 with such a system.

Note: although there is some level of separation between generic code and XCP-ng/Alma-specific code, this is essentially a prototype, don't count on reusability yet.

status

• prototype
• content limitations
  • can only generate part of the packages that make up XCP-ng, some of them not even having the XCP-ng patches added onto the newer upstream version
  • x86_64-v2 arch only
• tooling limitations
  • no caching of RPMs downloaded from upstream Alma/EPEL/Fedora
  • native build only (no cross-compilation)
  • no support for some features we don't seem to need yet:
    • rpm dynamic build requirements

quick start

Setup a build environment:

. oe-init-build-env

Build everything (packages, repository) up to an installation image:

bitbake install-image-iso

recipe classes

Those are the .bb files under meta-xcpng/recipes-*/.

xcp-ng-rpm

Describes how to build RPM packages (artifacts) from a specfile in a RPM source repository, and how to produce repositories including all packages required to install those RPM packages.

Minimal example: libempserver is a package without any build dependencies, and whose RPM artifacts have no dependency outside of the upstream distro (i.e. none that we build from another recipe).

Baseline example: xs-opam-repo is a package declaring both build-time dependencies (DEPENDS) and run-time depends (RDEPENDS) on other recipes. Both are slightly different from the BuildRequires and Requires fields in the RPM specfile:

• the recipe fields use the name of the recipe (which is the name of the SRPM package, and the name of the git repository holding it), whereas the specfile fields refer to (something provided by) RPM packages built out of those
• the specfile fields do not know which packages come from upstream distro, and which ones we build from other recipes

Complex example: xen, in addition to the above, currently relies, both for at build-time and at run-time, on Fedora packages we hope to get into upstream EPEL, but are not yet there, and we currently pull the RPMs from Fedora directly rather than building them ourselves. This is done by specifying direct URLs to the relevant RPMs, respectively using EXTRA_UPSTREAM_DEPENDS and EXTRA_UPSTREAM_RDEPENDS.

The guidelines we use for AlmaLinux10-compatible RPMs is:

• pick most packages from Fedora 41
• pick python packages from Fedora 40 (which has the same python interpreter version)

filling those *DEPENDS variables

Looking at the specfile with grep is the best way to identify build dependencies, looking at the generated RPMs's Requires fields is the best way to identify runtime ones.

If any packages are missed for retrievial by one task, the next step one will error out and you will see in the task log what packages should be added to the previous task. E.g., if you miss a recipe in DEPENDS (used by the do_collect_managed_builddeps task, then the do_fetch_upstream_builddeps will try to find the relevant packages in Alma, and will fail (unless we're talking about a package that also exists in Alma, which adds yet another reason to avoid that situation).

dev cheat sheet

You will find in the conf/local.conf installed in your build tree when it got created a few examples of tuning for some specific tasks, including:

• activation of ccache
• building from a local xcp-ng-rpms commit to test it before pushing it