Comment 1 for bug 1934108

For further info, I'm seeing this on a couple units of etcd as well.

running the command manually, you see this error

root@juju-f98bb9-2-lxd-1:/sys/fs/cgroup/freezer# etcd.etcdctl version
cannot open cgroup hierarchy /sys/fs/cgroup/freezer: No such file or directory

But oddly, the cgroup exists and should be readable, but may not be available due to snap confinement. I'd guess that cgroups got a new plug in upstream snapd, hence the effect taking place after restart. It seems that the issue is the charm's attempt to run etcdctl version command, but that etcd itself is running and functioning.

root@juju-f98bb9-2-lxd-1:/sys/fs/cgroup/freezer# find -ls
       32 0 drwxrwxr-x 4 nobody root 0 Jul 20 20:25 .
       33 0 -rw-rw-r-- 1 nobody root 0 Oct 1 21:03 ./cgroup.procs
       38 0 -r--r--r-- 1 nobody nogroup 0 Jan 7 23:31 ./freezer.self_freezing
      120 0 drwxr-xr-x 2 root root 0 Jul 20 20:25 ./snap.etcd
      121 0 -rw-r--r-- 1 root root 0 Jul 20 20:25 ./snap.etcd/cgroup.procs
      126 0 -r--r--r-- 1 root root 0 Jul 20 20:25 ./snap.etcd/freezer.self_freezing
      123 0 -rw-r--r-- 1 root root 0 Jul 20 20:25 ./snap.etcd/tasks
      127 0 -r--r--r-- 1 root root 0 Jul 20 20:25 ./snap.etcd/freezer.parent_freezing
      125 0 -rw-r--r-- 1 root root 0 Dec 20 00:00 ./snap.etcd/freezer.state
      124 0 -rw-r--r-- 1 root root 0 Jul 20 20:25 ./snap.etcd/notify_on_release
      122 0 -rw-r--r-- 1 root root 0 Jul 20 20:25 ./snap.etcd/cgroup.clone_children
       35 0 -rw-rw-r-- 1 nobody root 0 Jul 20 20:22 ./tasks
       39 0 -r--r--r-- 1 nobody nogroup 0 Jan 7 23:31 ./freezer.parent_freezing
       37 0 -rw-r--r-- 1 nobody nogroup 0 Jan 7 23:31 ./freezer.state
       88 0 drwxr-xr-x 2 root root 0 Jul 20 20:23 ./snap.lxd
       89 0 -rw-r--r-- 1 root root 0 Jul 20 20:23 ./snap.lxd/cgroup.procs
       94 0 -r--r--r-- 1 root root 0 Jul 20 20:23 ./snap.lxd/freezer.self_freezing
       91 0 -rw-r--r-- 1 root root 0 Jul 20 20:23 ./snap.lxd/tasks
       95 0 -r--r--r-- 1 root root 0 Jul 20 20:23 ./snap.lxd/freezer.parent_freezing
       93 0 -rw-r--r-- 1 root root 0 Dec 20 00:00 ./snap.lxd/freezer.state
       92 0 -rw-r--r-- 1 root root 0 Jul 20 20:23 ./snap.lxd/notify_on_release
       90 0 -rw-r--r-- 1 root root 0 Jul 20 20:23 ./snap.lxd/cgroup.clone_children
       36 0 -rw-r--r-- 1 nobody nogroup 0 Jan 7 23:31 ./notify_on_release
       34 0 -rw-r--r-- 1 nobody nogroup 0 Jan 7 23:31 ./cgroup.clone_children