Current situation

For building kernel modules or debug symbols, the devcontainer in systemd-nspawn (or the third-party Docker images) has to be used.

Impact

The UX with the second environment that's persisted to disk and only has access to some host paths is not the best.

Ideal future situation

Build developer container packages into a systemd-sysext image and publish as release artifact and as signed update payload for consumption as official Flatcar extension. It gets activated through a line with NAME in /etc/flatcar/enabled-sysext.conf.

Implementation options

Call it Flatcar "dev", Flatcar "devtools", or Flatcar "compiler" extension.
Consider to provide debug symbols for the base image as part of it or in a second extension.

Additional information

Depending on when the "extra" extension gets implemented, make sure that there is no conflict in files they provide. If the "dev" extension requires tools from "extra", activation of "extra" will be implied by "dev".

Note that for debugging with gdb the current library path is something like /build/ARCH but it should become the host path.