Backup of LXC containers to NFS mount fail

[rogierl]

I have my Synology NAS mounted as NFS share to proxmox 7.0-11. Now I'm perfectly able to backup the VMs to the synology, but I cannot backup LXC containers.
The error which I get can be found below. Please notice that backing up LXC containers to local storage works fine!

INFO: starting new backup job: vzdump 106 --mode snapshot --node pve --compress zstd --remove 0 --storage synology
INFO: Starting Backup of VM 106 (lxc)
INFO: Backup started at 2021-08-26 14:01:50
INFO: status = running
INFO: CT Name: unifi
INFO: including mount point rootfs ('/') in backup
INFO: backup mode: snapshot
INFO: ionice priority: 7
INFO: create storage snapshot 'vzdump'
WARNING: You have not turned on protection against thin pools running out of space.
WARNING: Set activation/thin_pool_autoextend_threshold below 100 to trigger automatic extension of thin pools before they get full.
Logical volume "snap_vm-106-disk-0_vzdump" created.
WARNING: Sum of all thin volume sizes (118.00 GiB) exceeds the size of thin pool pve/data and the amount of free space in volume group (14.75 GiB).
INFO: creating vzdump archive '/mnt/pve/synology/dump/vzdump-lxc-106-2021_08_26-14_01_50.tar.zst'
INFO: tar: /mnt/pve/synology/dump/vzdump-lxc-106-2021_08_26-14_01_50.tmp: Cannot open: Permission denied
INFO: tar: Error is not recoverable: exiting now
INFO: cleanup temporary 'vzdump' snapshot
Logical volume "snap_vm-106-disk-0_vzdump" successfully removed
ERROR: Backup of VM 106 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/synology/dump/vzdump-lxc-106-2021_08_26-14_01_50.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 --rsyncable '--threads=1' >/mnt/pve/synology/dump/vzdump-lxc-106-2021_08_26-14_01_50.tar.dat' failed: exit code 2
INFO: Failed at 2021-08-26 14:01:50
INFO: Backup job finished with errors
TASK ERROR: job errors

 

[oguz]

hi,

INFO: tar: /mnt/pve/synology/dump/vzdump-lxc-106-2021_08_26-14_01_50.tmp: Cannot open: Permission denied

try setting the tmpdir parameter in /etc/vzdump.conf to a writable directory (backups for containers are made within the context of the unprivileged user in the container, which doesn't have write access to the folder on your NAS)

 

[rogierl]

hi,


try setting the tmpdir parameter in /etc/vzdump.conf to a writable directory (backups for containers are made within the context of the unprivileged user in the container, which doesn't have write access to the folder on your NAS)

Thanks for your help! Do you have any suggestions? What directory can I use for that? /tmp ?

 

[oguz]

What directory can I use for that? /tmp ?

/tmp can be too small for big disks. you can try /var/tmp

 

[rogierl]

/tmp can be too small for big disks. you can try /var/tmp

Thanks; this worked! Now I'm wondering... isn't this something which should be solved in a more structural way?