Proxmox/ZFS: Containers do not start after upgrade

Publication date: 2020-02-28

Issue: Proxmox cannot start containers and ZFS mounts complains on non-empty directories

After upgrading to Debian Buster and a new Proxmox version, containers did no longer start.

Solution: Allow mounting ZFS filesystems into non-empty existing directory

In "/lib/systemd/system/zfs-mount.service" change

ExecStart=/sbin/zfs mount -a

ExecStart=/sbin/zfs mount -O -a

Afterwards restart.

Hint towards the solution

There are some forum posts from 2016 pointing to the solution suggested above:

https://forum.proxmox.com/threads/proxmox-ve-zfs-does-not-mount-on-boot.15387/

https://forum.proxmox.com/threads/mount-zfs-when-directory-not-empty.29657/