Strange problem running vzdump command

Apr 30, 2026
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Hello,

I am seeing a very strange error when running backups (via vzdump) from command line instead of via the GUI.

I have created a backup job on my datacenter:
Code:
vzdump: backup-a4770096-56f9
        schedule weekly
        compress zstd
        enabled 0
        fleecing 0
        mode snapshot
        node pve4
        notes-template {{guestname}}
        notification-mode notification-system
        prune-backups keep-last=1
        repeat-missed 0
        storage NAS1
        vmid 136

When I run this backup with 'run now', it works and I get the log:

Code:
INFO: starting new backup job: vzdump 136 --fleecing 0 --storage NAS1 --prune-backups 'keep-last=1' --all 0 --node pve4 --notification-mode notification-system --compress zstd --mode snapshot --notes-template '{{guestname}}'
INFO: Starting Backup of VM 136 (lxc)
INFO: Backup started at 2026-08-05 12:11:51
INFO: status = running
INFO: CT Name: ExportSanctionChecker
INFO: including mount point rootfs ('/') in backup
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: create storage snapshot 'vzdump'
freeze guest filesystem
Creating snap: 10% complete...
Creating snap: 100% complete...done.
thaw guest filesystem
/dev/rbd4
INFO: creating vzdump archive '/mnt/pve/NAS1/dump/vzdump-lxc-136-2026_08_05-12_11_51.tar.zst'
INFO: Total bytes written: 663418880 (633MiB, 30MiB/s)
INFO: archive file size: 189MB
INFO: adding notes to backup
INFO: prune older backups with retention: keep-last=1
INFO: removing backup 'NAS1:backup/vzdump-lxc-136-2026_08_05-12_09_27.tar.zst'
INFO: pruned 1 backup(s) not covered by keep-retention policy
INFO: cleanup temporary 'vzdump' snapshot
Removing snap: 100% complete...done.
INFO: Finished Backup of VM 136 (00:00:24)
INFO: Backup finished at 2026-08-05 12:12:15
INFO: Backup job finished successfully
TASK OK

Whe I run the same vzdump command from the console (as root), I get a report:

Code:
vzdump 136 --notes-template '{{guestname}}' --compress zstd --node pve4 --mode snapshot --notification-mode notification-system --all 0 --fleecing 0 --storage NAS1 --prune-backups 'keep-last=1'


136: 2026-08-05 12:11:01 INFO: Starting Backup of VM 136 (lxc)
136: 2026-08-05 12:11:01 INFO: status = running
136: 2026-08-05 12:11:01 INFO: CT Name: ExportSanctionChecker
136: 2026-08-05 12:11:01 INFO: including mount point rootfs ('/') in backup
136: 2026-08-05 12:11:01 INFO: backup mode: snapshot
136: 2026-08-05 12:11:01 INFO: ionice priority: 7
136: 2026-08-05 12:11:01 INFO: create storage snapshot 'vzdump'
136: 2026-08-05 12:11:02 INFO: creating vzdump archive '/mnt/pve/NAS1/dump/vzdump-lxc-136-2026_08_05-12_11_01.tar.zst'
136: 2026-08-05 12:11:02 INFO: tar: failed to return to initial working directory: Permission denied
136: 2026-08-05 12:11:02 INFO: cleanup temporary 'vzdump' snapshot
136: 2026-08-05 12:11:02 ERROR: Backup of VM 136 failed - command 'set -o pipefail && lxc-usernsexec -m u:0:100000:65536 -m g:0:100000:65536 -- tar cpf - --totals --one-file-system -p --sparse --numeric-owner --acls --xattrs '--xattrs-include=user.*' '--xattrs-include=security.capability' '--warning=no-file-ignored' '--warning=no-xattr-write' --one-file-system '--warning=no-file-ignored' '--directory=/mnt/pve/NAS1/dump/vzdump-lxc-136-2026_08_05-12_11_01.tmp' ./etc/vzdump/pct.conf ./etc/vzdump/pct.fw '--directory=/mnt/vzsnap0' --no-anchored '--exclude=lost+found' --anchored '--exclude=./tmp/?*' '--exclude=./var/tmp/?*' '--exclude=./var/run/?*.pid' ./ | zstd '--threads=1' >/mnt/pve/NAS1/dump/vzdump-lxc-136-2026_08_05-12_11_01.tar.dat' failed: exit code 2
 
Cause: vzdump for unprivileged containers runs tar through lxc-usernsexec, which remaps uid/gid 0 → 100000 for the duration of the archive


When Proxmox runs the job itself (GUI/scheduler), the worker's cwd is /, which is world-traversable, so it just works. Nothing wrong with your CT or storage config.


Fix: cd / (or /tmp) before running vzdump manually: