When adding a sysext image to the system and manuall merging it, a
later "systemctl (re)start systemd-sysext" won't work because "merge"
refuses to work when something is merged already. Another problem with
"merge" at start plus "unmerge" at stop is that a service restart can't
make use of the new MOVE_MOUNT_BENEATH in the future even which would
only be available in "refresh". It also prepares us for setting up the
merged overlay for the sysroot from the initrd already, which also
would lead to the mentioned start problem of the service (One
optimization could be to skip the loading but only if we are sure that
all images were loaded and weren't modified since - this assumption is
hard because early services could want to inject a sysext, too).
Use "refresh" on service start to fix the problem that the service
can't start as soon as a manual merge was done. Also add a reload
action that allows to issue "systemctl reload systemd-sysext" and it
will make use of MOVE_MOUNT_BENEATH once we implement this in
systemd-sysext refresh (and it's available from the kernel).
The /usr/lib/extensions/ location for systemd-sysext images is not
supported anymore. In https://github.com/systemd/systemd/pull/26013
systemd-confext images got introduced and we can list its path under
/usr instead.
The loading of an extension image from a symlink "NAME.raw" to
"NAME-VERSION.raw" failed because the release file name check worked
with the backing file of the loop device which already resolves the
symlink and thus the found name "NAME-VERSION" mismatched "NAME".
Pass the original filename and use it instead of the backing file
when available. This fixes the loading of "NAME.raw" extensions which
are a symlink to "NAME-VERSION.raw" as, e.g., may be the case when
systemd-sysupdate manages multiple versions.
Fixes https://github.com/systemd/systemd/issues/24293
While I had tested that a symlink to /dev/null works to "mask" a sysext
I must have gotten something wrong and thus the instructions in
519c2f0d6b don't work. What works,
at least at the moment, is to instead have an empty directory with the
extension name under /etc/extensions/.
Correct the info in the man page and add a test for it.
When an extension image has binaries they should match the host
architecture. Currently there is no way to specify this requirement.
Introduce an ARCHITECTURE field in the extension's release file that
may be set to prevent loading on the wrong host architecture.
Since this new field is introduced late, we don't want to make
specifying it mandatory as it would break existing sysext images.
See https://github.com/systemd/systemd/issues/24061
A sysext image that merely contains static binaries has no dependency
on the host distribution and should be able to be used anywhere.
Support the special '_any' value for the ID field in the extension to
opt-out of ID and VERSION_ID/SYSEXT_LEVEL matching.
See https://github.com/systemd/systemd/issues/24061
While Type=file works because it seems to be the default, the line gets
ignored as printed on the stderr output.
Use the correct value "regular-file" for the target type.
A read-only /usr may ship a sysext image by default and the user wants
to opt out. Currently it's not clear how to do this.
Document that a /dev/null symlink in /etc/extensions/ works to "mask" a
sysext image in a folder with lower precedence.
While overlaying files with a sysext can be useful, it may lead to
unexpected problems depending on when a process got started and which
version of the file it gets.
Call out that overlaying files is possible but don't recommend to make
use of it.
Kai Lueke