Hi Martin,
Am 01.12.2016 um 10:20 schrieb Martin Pitt:
Hello André,
André Hartmann [2016-12-01 9:50 +0100]:
So I naively created the following link structure (which works):
/etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service ->
/mnt/writeable/systemd-timesyncd ->
/lib/systemd/system/systemd-timesyncd.service
But if I remove /mnt/writeable/systemd-timesyncd and reboot,
the command 'timedatectl status' still reports enabled, which is unexpected.
This is because systemd only really looks at the foo.wants/bar.service
symlink itself -- it's actually okay for that to point into
nothingness. I think this is mostly due to the fact that the actual
units can be in /etc, /usr, or /run, and even move between those.
The funny thing is, that foo.wants/bar.service can also point to
../baz.service, i.e. the name of the symlink does not matter. Somehow
systemd seems to recognize when such a link is created and "cache" this
result somewhere.
In other words: once this symlink is valid, you cannot invalidate it by
make it a dangling symlink, you have to remove it. Can somebody confirm
this observation?
And ... any other ideas how to enable/disable timesyncd?
I'd like to keep as much as possible read-only, including the
configurations.
Thanks, Andre
For example, you might have
/usr/lib/systemd/system/foo.service
/usr/lib/systemd/system/multi-user.target.wants/foo.service → ../foo.service
and then override this with
/etc/systemd/system/foo.service
Then multi-user.target will still use the unit from /etc, *not* the
one from /usr, even though that's where the symlink points to. In
this case this is pretty obviously the correct behaviour; in your case
it's admittedly confusing.
I'm not entirely sure if dangling symlinks should be counted as
"enabled", but this should least explain your observation.
Martin
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