To me this is the last major basic functionality that couldn't be
configured via credentials: the network.
We do not invent any new format for this, but simply copy relevant creds
1:1 into /run/systemd/network/ to open up the full functionality of
networkd to VM hosts.
For shutdown, we queue shutdown.target/start, so in every unit which should be
stopped *before* shutdown, we need both Conflicts and an ordering dependency
with shutdown.target (either Before= or After= would work, because stop jobs
are always ordered before start jobs).
For initrd transition, we queue initrd-switch-root.service/isolate. This
automatically creates a /stop job for every running unit without
IgnoreOnIsolate. But no ordering dependency is created, unless the unit has a
(possibly transitive) ordering dependency on initrd-switch-root.service.
Since most units must stop before the transition, we should add the ordering
dependency. It is nicer to use Before=initrd-switch-root.target for this.
initrd-switch-root.target is ordered before initrd-switch-root.service, so
the effect it the same when both are in a transaction.
Fixes#23745.
To also cover the case where somebody is emergency mode in the initrd and
queues initrd-switch-root.service/start (not isolate), also add
Conflicts=initrd-switch-root.target, so various units are stopped properly.
This extends 2525682565 to cover all the other
services that are touched. It could be consider "operator error", but it's
easy to make and it's nicer if we can make this more foolproof.
The block is reordered and split to have:
1. description + documentation
2. (optionally) conditions
3. all the dependencies
I think it's easier to read the units this way.
Also, the Conflicts+Before is seperated out to separate lines.
The ordering dependency is "fake", because it could just as well be
After=, we are adding it to force ordering wrt. shutdown.target, and
it plays a different role than the other Before=, which are about a
real ordering on boot.
We don't need two (and half) templating systems anymore, yay!
I'm keeping the changes minimal, to make the diff manageable. Some enhancements
due to a better templating system might be possible in the future.
For handling of '## ' — see the next commit.
