Bug#777164: systemd: libvirt cgroups start to disappear from machine.slice after systemctl daemon-reload

[Christian Seiler]

Control: severity -1 serious
Control: tags -1 + patch

Dear Maintainers,

this doesn't only affect libvirt/KVM somewhat, but it also breaks LXC,
which also uses its own cgropus. lxc-attach will stop working once
systemctl daemon-reload has been issued with a running LXC instance.
Since this breaks two unrelated pieces of software, I think the
severity 'serious' is justified.[1]

I've backported the commit that was used to fix this upstream and
attached it to this mail. The original commit was committed after the
Delegate= property was added to units, I left out that part (i.e. it
will only consider slice units). I've tested the patch and libvirt/KVM
and LXC now remain in their cgroups with systemctl daemon-reload (I've
tested both here).


(Side note: daemon-reload alone is not necessarily sufficient to
reproduce this issue, but if one starts a unit afterwards, it will
occur. Therefore, using systemctl daemon-reload + systemctl restart
exim4.service will consistently reproduce the issue on my systems.)



Christian

[1] I do feel a bit bad because I've already reported / upgraded the
severity of a couple of systemd bugs, but I do think that in every
case I can justify this being RC... Please don't consider this to be
criticism of your work, I just want to make sure that systemd in Jessie
is in a very good shape.
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