It looks like what broke your setup is actually a bugfix in LXC wrt config inheritance.
Your config contains:
- lxc.mount.auto =
- lxc.mount.auto = cgroup:mixed
This instructs LXC (and that wasn't implemented right at first) to wipe all of lxc.mount.auto, and then set cgroup:mixed.
Doing so unsets the default which did contain sys:mixed, causing the breakage you had.
So the issue is that LXC actually does what you ask it to do now :)
Just re-read through this whole bug.
It looks like what broke your setup is actually a bugfix in LXC wrt config inheritance.
Your config contains:
- lxc.mount.auto =
- lxc.mount.auto = cgroup:mixed
This instructs LXC (and that wasn't implemented right at first) to wipe all of lxc.mount.auto, and then set cgroup:mixed.
Doing so unsets the default which did contain sys:mixed, causing the breakage you had.
So the issue is that LXC actually does what you ask it to do now :)