Best Practive Backup ext4 Mountpoints (.raw-files)

[Pascal1991]

Hello everyone,

I’m running into an issue that I can’t quite wrap my head around.

I’ve been using Proxmox Backup Server (PBS) for about a week now and I’m very happy with the setup so far. I’ve already solved a few roadblocks by reading through this forum, but I couldn’t find a solution for the following problem.

I have an iSCSI LUN mounted on PBS (I know this isn’t best practice, but this is a homelab). PBS is configured as a storage target in Proxmox VE, and backing up and restoring VMs and LXCs works perfectly.

The problem is backing up mount points from unprivileged containers (all of my containers are unprivileged).

I can back up a mount point manually using something like:

proxmox-backup-client backup 158.pxar:/mnt/pve/media/images/158 \
--repository 'xxxxx'
--backup-id 'ct-158-mp0'

However, this ends up backing up the underlying .raw file. The raw file is 4 TB in size, while only about 1 TB is actually used, which makes this approach impractical.
What options do I have to efficiently back up mount points from unprivileged containers without backing up the full raw disk size?

Thanks in advance for any pointers.

 

[Pascal1991]

Update:
I tried to run proxmox-backup-client inside the container.
But this seems not to work because of the a permission issue. (Which i dont understand why there is one).

I used:
proxmox-backup-client backup test.pxar:/test/ \
--repository 'xxxx@pbs@xxx.xxx.xx.xxxroxmox-backup' \
--backup-id 'test'

result:
root@totodile:~# proxmox-backup-client backup test.pxar:/test/ --repository 'xxxx@pbs@xxx.xxx.xx.xxxroxmox-backup' \ --backup-id 'test'

Starting backup: host/test/2026-01-04T07:48:57Z
Client name: totodile
Starting backup protocol: Sun Jan 4 08:48:57 2026
Error: permission check failed.
root@totodile:~#

What kind of permission check fails here? I used the token, that works on the host.

 

[Pascal1991]

solved.