[SOLVED] Backup to Dropbox works for VM but not LXC

[Sandbo]

Hi,

I am trying to setup an automatic backup of the disk image to dropbox for my VM.
First I install dropbox on my proxmox root, then I created a symlink folder where then I assign as the backup directory in the GUI.
With this, I have no problem backing up a VM and have it uploaded to dropbox.

However, when I tried to do the same for LXC it fails:

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-102-disk-0_vzdump" created.
WARNING: Sum of all thin volume sizes (<352.02 GiB) exceeds the size of thin pool pve/data and the amount of free space in volume group (<16.00 GiB).
INFO: creating archive '/CSQT_RAID1/BKUPs/BKUP_CSMS1/dump/vzdump-lxc-102-2020_02_24-03_33_25.tar.lzo'
INFO: tar: /CSQT_RAID1/BKUPs/BKUP_CSMS1/dump/vzdump-lxc-102-2020_02_24-03_33_25.tmp: Cannot open: Permission denied
INFO: tar: Error is not recoverable: exiting now
INFO: remove vzdump snapshot
Logical volume "snap_vm-102-disk-0_vzdump" successfully removed
ERROR: Backup of VM 102 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=/CSQT_RAID1/BKUPs/BKUP_CSMS1/dump/vzdump-lxc-102-2020_02_24-03_33_25.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' ./ | lzop >/CSQT_RAID1/BKUPs/BKUP_CSMS1/dump/vzdump-lxc-102-2020_02_24-03_33_25.tar.dat' failed: exit code 2
INFO: Failed at 2020-02-24 03:33:28
INFO: Backup job finished with errors
TASK ERROR: job errors

Any idea would be appreciated.

 

[Stoiko Ivanov]

I guess the container for dropbox is unprivileged - in that case the backup is done with root inside the container and that is UID 100000 on the host:
make sure that the backup-storage is writable by all users (or at least by UID 100000)

I hope this helps!

 

[Sandbo]

I guess the container for dropbox is unprivileged - in that case the backup is done with root inside the container and that is UID 100000 on the host:
make sure that the backup-storage is writable by all users (or at least by UID 100000)

I hope this helps!

Thanks a lot for your reply.
The container is indeed unprivileged and what you suggest is highly likely the case.

I didn't know the backup was done by the root of the container, but not of the Proxmox host, and this is probably the reason.

 

[Stoiko Ivanov]

Let us know if that fixed your problem (and if yes - please mark the thread as 'SOLVED')
Thanks!

 

[Sandbo]

Let us know if that fixed your problem (and if yes - please mark the thread as 'SOLVED')
Thanks!

Yes, I can confirm it solves my problem. Just a bit more:
Apart from setting the destination folder to 777, I do have to set the /root and /root/Dropbox directories to 755, as I understand that the execution bit is required in order for the child directory to be written by other users.

I might just work on setting a special group for the backup task later to avoid exposing the folder to everyone though.

 

[Stoiko Ivanov]

glad that solved the issue!
Please consider the security implications of changing the permissions of /root (it does contain sensitive data)
maybe creating a dedicated backup user seems like a better alternative

 

[Sandbo]

glad that solved the issue!
Please consider the security implications of changing the permissions of /root (it does contain sensitive data)
maybe creating a dedicated backup user seems like a better alternative

Yes, I think the simplest solution is just to move the Dropbox folder out of root to my attached drive.
Thanks again for your help!