Hello my dears,
I am still relatively inexperienced and new to self-hosting. So far, I have always managed to solve my problems with trial and error, help, instructions and guides. However, I’m desperate with this one and can’t find a solution. I have already written a post about this in the (german) CB forum but am now relying on the concentrated NC power of this board.
I have installed the latest, updated Ubuntu Server LTS version on a MinisForum GK41. It runs Docker, which I visualize with Portainer. It runs several containers (including Wireguard and Nextcloud). Remote access and daily work with my Nextcloud (current, stable version) works perfectly.
I have installed OMV on my RaspberryPi and mounted an external WD Elements there and made it available as a NAS in the network. Updating Windows (Windows restore) and MacOS (via Timemachine) works flawlessly.
I have already successfully added the NAS as external storage to Nextcloud. In the app or on the NC web interface, I can move data from the server to the NAS and vice versa.
My problem: the Nextcloud backup app. This is set up but there still seem to be problems.
If I switch to the admin view of Backup, a red message appears directly in the top right corner: “App data cannot be retrieved”.
If I want to create the restore point “now”, the red warning appears: “The creation of a restore point has been requested and will start soon.”. This disappears after a few hours when I reload the interface. However, a restore point has not been created.
I have specified two locations for restore points:
(a) local::/var/lib/docker/volumes/external-disk/_data/subfolder (my attempt to set up an SSD, connected to the MinisForum server, as a backup location did not work either).
b) smb::nastobo@192.168.178.29//NASBerry//Backup_Nextcloud/Unterordner
The history/schedule shows the scheduled backup processes, runs down to “Next full restore point: in 5 minutes” and stops at that point.
Under app data I can choose between local, 3a) or 3b), but I can specify a path in the path specification, but I cannot confirm any variant with “Set for app data”.
I have already created a cronjob script. This triggers Cronjob.php every 5 minutes (I can also see this in the Nextcloud settings under Basic settings → Background jobs).
I know that there are very individual solutions for backups, but I would be happy if I could implement this as planned and select my NAS as the backup location.
Thank you very much and if you have any questions, just let me know 
!
Best regards
Erik