transmission-daemon settings gone after system halt

[Thomas M Steenholdt]

Ubuntu-15.10, amd64
systemd-225-1ubuntu9
transmission-daemon-2.84-1ubuntu1

I've noticed more than once, that "halt" can cause transmission-daemon to loose it's settings. AFAIK, "halt" is not that different from "poweroff" or "reboot" in regards to the shutdown sequence, so it is probably a problem for those as well.

What I've noticed is that after my system comes back up after being halted, transmission-daemon won't start, citing config issues. Looking at /etc/transmission-daemon/settings.json, it's there but it's empty.

This does not happen every time, but I've seen it on at least 3 different occasions.

My guess (and I'm relatively new to systemd) is that while the transmission-daemon systemd unit-file wants to start after network.target, there is nothing that would prompt a "stop" of the service during shutdown. This seems to leave a race where the transmission-daemon is killed too close to remounting the / filesystem read-only, giving the daemon enough time to truncate it's config, yet making it impossible for the daemon to write it's settings, as it likes to do on "stop".

My / filesystem is XFS, but that does not seem to have anything to do with this.

I'm still looking for a way to map out the dependencies of systemd on shutdown, but it seems to me that perhaps adding Require=network.target to the unit-file might cause the daemon to stop early and solve this issue.

Please let me know if you need anything else

[Thomas M Steenholdt (tmus)]

I was wrong. It appears as if the XFS filesystem on / is the actual culprit here.
The way XFS works, makes it lose last-second changes such as the new settings file written by transmission-daemon, whet the power is cut after halt. I've added a "sync" to my UPS power-off script and everything appears to be much more stable now.

[Thomas M Steenholdt (tmus)]

After this, I have no indication that anything should be wrong with transmission-daemon regarding this, so I'm closing the case.