mkdir /mnt/vzsnap0 permission denied proxmox: it’s not /mnt, it’s your storage

mkdir /mnt/vzsnap0 permission denied proxmox is almost never about /mnt permissions. The real problem is your backup storage doesn’t support snapshots. Here’s how to check and fix it.

Why the error happens

When you back up an LXC container, Proxmox first creates a snapshot of the container’s filesystem. It mounts that snapshot at /mnt/vzsnap0 and then copies the data. If the storage where the container lives doesn’t support snapshots, the mount fails and you get that stupid permission denied error.

Note: /mnt itself is usually writable by root, and the backup runs as root. So chmod 777 /mnt is a waste of time and a security hole. Don’t do that.

Check your storage type

First, find out what storage your container is on:

pct config <VMID> | grep rootfs

Then check the storage type in the Proxmox web UI under Datacenter → Storage, or run:

pvesm status

Common culprits:

• Directory storage on ext4 or xfs: no snapshot support. You’ll get this error.
• ZFS: supports snapshots, but only if the dataset is set up correctly.
• LVM-thin: supports snapshots, but not if the container is on a plain LVM volume.
• NFS: depends on the underlying filesystem. If it’s ext4, no snapshots.

If your storage doesn’t support snapshots, you have two options: move the container to a snapshot-capable storage, or change the backup mode to stop instead of snapshot. Stop mode shuts down the container during backup, so no snapshot is needed. It’s less convenient but works everywhere.

Fix it without moving storage

If you can’t move the container, just change the backup mode. In the web UI, go to the container → Backup → Edit, and set Mode to Stop. Or from the command line:

vzdump <VMID> --mode stop --storage <backup-storage>

That will work on any storage type. The container will be down for the duration of the backup, so schedule it for low-usage hours.

If you’re on ZFS

ZFS supports snapshots, but sometimes the dataset has the wrong properties. Make sure the container’s dataset is mounted and has the right mountpoint. You can list datasets with:

zfs list

If the container’s dataset is there, try a manual snapshot to see if it works:

zfs snapshot rpool/data/subvol-<VMID>-disk-0@test

If that fails, you have a ZFS issue, not a Proxmox one.

My take

This error is annoying because the message points you in the wrong direction. It’s not about /mnt permissions; it’s about storage capabilities. Before you go chmod’ing things, check your storage type. And if you’re on a homelab, keep it simple: use directory storage with stop-mode backups, or switch to ZFS if you want snapshot backups. Don’t overcomplicate it.

If you’re dealing with other weird Proxmox errors, check out my post on IO delay or UID/GID mapping in unprivileged containers.

Part of Proxmox in a homelab — the backup and storage section.