Proxmox: Snapshots not possible for containers with bind mount

Publication date: 2024-06-08

Issue: Snapshots not possible for Proxmox containers with bind mount

I have many containers that use bind mounts to the host for their persistent storage. This looks as follows in the lxc container config:

mp0: /home/containers/dh-test,mp=/home

However, with such bind mounts it is no longer possible to create snapshots for the storage of such containers. The Proxmox UI shows: "The current guest configuration does not support taking new snapshots".

This is quite annoying to me since snapshots are a very helpful feature.

Solution: Use raw lxc directives

Instead of using mpX: ..., one can use lxc directives directly as follows:

lxc.mount.entry: /directory/on/host directory/in/container none bind,rw 0 0

Note the missing leading slash in the second argument. That is important.

Example:

#mp0: /home/containers/dh-test,mp=/home
#can be replaced by:
lxc.mount.entry: /home/containers/dh-test home none bind,rw 0 0

The directory to mount to within the container must already exist. To be tolerant on that, one can add create=dir:

lxc.mount.entry: /home/containers/dh-test home none bind,rw,create=dir 0 0

Using lxc.mount directly allows for more powerful options, e.g. for including submounts as well (using rbind):

lxc.mount.entry: /vault vault none rbind,rw,create=dir,optional 0 0

Hint towards the solution

There is a helpful thread in the Proxmox forum on this, see https://forum.proxmox.com/threads/why-do-bind-mounts-prevent-snapshots.85495/. Apparently, Proxmox considers the restriction a feature.