Overlay Extension Builder

Build system extensions for live systemd-sysupdate managed systems using mkosi

Usage: overlay-ext [OPTIONS]

Options:
  -f, --force    Whether to forceably rebuild the overlay for the booted deployment
  -h, --help     Print help
  -V, --version  Print version

Warning

This program is very early in development and will probably not work for most systems.

This program is designed to build a system extension containing additional packages built against the same snapshot as the base system. It is intended primarily for image-based systems managed by systemd-sysupdate.

The actual sysext builds are handled by mkosi and the end user can configure which packages are included at /etc/overlay-ext/mkosi/, which acts as a fully-featured mkosi directory.

When building the sysext with mkosi, the following template is used: overlay-ext-skeleton.

Some systems may require os-specific hacks. Currently only implemented for Arch Linux with a custom db path of /usr/lib/sysimage/lib/pacman, but can be adapted to other distributions by matching os-release files.

Requirements

In order to use this tool, the following requirements must be met by the system:

• The system is installed and updated via systemd-sysupdate, and installed /usr trees are located on physical partitions. Loopback files may be supported at some point, but are not currently.

• The package database is included on the image. This also means that if the package manager does not put it in /usr, it must be copied there.

• The image is built against a fixed snapshot, e.g. the Arch Linux Archive. This is achieved in mkosi using the configuration option Snapshot=

• In /etc/os-release, VERSION_ID is populated and updated every single image version. I may change this to SYSEXT_LEVEL later for better support for Fedora.

• In /etc/os-release, a custom field IMAGE_SNAPSHOT is set to a valid mkosi snapshot reference, either grabbed from the build itself or replicated to be what it would be if using another buildsystem (typically this would be YYYY/MM/DD)

Note that the system need not contain a package manager, but mkosi will delete package metadata by default if the package manager is not included on the final image.