The version option is needed if you want to implement partition &
systemd-boot based A/B booting where the version information is encoded
in the files on the ESP. See systemd-sysupate docs for more details on
this:
https://www.freedesktop.org/software/systemd/man/latest/sysupdate.d.html
Note, however, that this is not *only* useful for systemd-sysupdate but
also for other similar updating tools/mechanisms.
Since the repart image is built on the build platform, use
`buildPackages` to construct the image. This allows for systemd-repart
images for cross-compiled nixos configurations to work properly.
literalExpression triggers the following error when building the
manual:
Cacheable portion of option doc build failed.
Usually this means that an option attribute that ends up in documentation (eg `default` or `description`) depends on the restricted module arguments `config` or `pkgs`.
Allow giving a custom package containing the `systemd-repart` binary.
Defaults to `pkgs.systemd`. This option opens up the possibility to use
a different package for the image builder and the system configuration.
For example, someone could use this option to build an image with a
patched systemd while still using the upstream nixpkgs systemd package
(i.e., `pkgs.systemd`) for the system configuration installed to the
created image.
Write the output of `systemd-repart` as a JSON file to
`$out/repart-output.json`.
Depending on the repart configuration, the output of `systemd-repart`
contains important information, for example, when creating verity
partitions:
> The verity root hash itself will be included in the output of
> systemd-repart.
See `Verity=` in repart.d(5).
