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How to Mount Synology NFS Share on Proxmox Backup Server

Synology DSM: 6.2.4-25556 Update 3, with BTRFS volume (required) [1.2.3.4]
Proxmox Backup Server: 2.1-1 [1.2.3.5]

On Synology

  1. Create a Shared Folder named xxxx on a BTRFS Volume (in this case, volume1), and give the user admin Read/Write permission.
  2. In the NFS Permissions tab, set:
  3. Privilege: Read/Write
  4. Squash: No mapping
  5. Security: sys
  6. Enabled Async: checked
  7. Allow Connections: unchecked
  8. Allow Subfolders: checked

On PBS

  1. Create and mount xxxx:

    mkdir /mnt/xxxx
mount 1.2.3.4:/volume1/xxxx /mnt/xxxx

  2. Add a Datastore named xxxx using the Backing path: /mnt/xxxx

  3. Open/Refresh the Datastore page (you should see Error 13 on xxxx).

  4. Unmount xxxx:

    umount /mnt/xxxx

Back on Synology

  1. Open Shared Folder xxxx, go to NFS Permissions, and change Squash to: Map all users to admin.
  2. Browse to xxxx and delete the .lock file.

Back on PBS

  1. Remount xxxx:

    mount 1.2.3.4:/volume1/xxxx /mnt/xxxx

  2. Open/Refresh the Datastore page (Error 13 should clear).

  3. Perform a host backup on a Proxmox Node to verify (e.g., backup the /etc folder which is usually small). This assumes you've already connected the Node to PBS (add Cluster Storage PBS Server).

    proxmox-backup-client backup nodeABC-etc.pxar:/etc --repository 1.2.3.5:xxxx

Notes

@grantph:
"I suspect this process highlights a bug in PBS datastore creation. It requires backup uid/gid 34:34 to create the .chunks folders but seems to prefer root after creation (for the UI and client backups). It wasn't necessary to create a backup user on Synology; that just led to uid/gid headaches."

Special thanks