Atomic rename error

A

ajimeno

New Member
Jan 28, 2026
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I have a proxmox backup server version 3.4.2, the backups are on a folder mounted via NFS and CIFS that originally is in a Synology.

The permissions are correct to write in the current proxmox backup server, but when I try to do the backup of the virtual machines in the cluster it sais this:
ERROR: backup finish failed: command error: unable to update manifest blob - Atomic rename failed for file "/mnt/backupsit/vm/102/2026-01-28T12:53:43Z/index.json.blob" - Permission denied (os error 13)

The version of NFS is 3 and the version of CIFS is 3.1.1
 
yes, it works:
root@bqvmproxmoxbackupit:/mnt/backupsit# sudo -u backup bash
backup@bqvmproxmoxbackupit:/mnt/backupsit$ touch testfile
mv testfile testfile2
rm testfile2
backup@bqvmproxmoxbackupit:/mnt/backupsit$ # touch testfile
backup@bqvmproxmoxbackupit:/mnt/backupsit$ #
mv testfile testfile2
backup@bqvmproxmoxbackupit:/mnt/backupsit$ ls -l
total 0
drwxr-xr-x 2 backup backup 0 Oct 14 12:43 ct
-rwxr-xr-x 1 backup backup 0 Jan 28 14:35 testfile2
drwxr-xr-x 2 backup backup 0 Jan 19 13:54 vm
backup@bqvmproxmoxbackupit:/mnt/backupsit$
 
Have you checked the ownership and permissions of the entire path of the offending file? Can you perform same operations in that path? With that file?
Have you checked your NAS log files? Can you increase verbosity of the logs on the NAS side? Essentially, the "permission denied" comes from the NFS/NAS layer.
I know you said that "permissions are correct", but something is clearly not working and there are no widespread user reports of similar issues. So that leads me to believe that it is something specific to your environment.

ls -ld /mnt/backupsit
ls -ld /mnt/backupsit/vm
ls -ld /mnt/backupsit/vm/102
id backup
mount | grep /mnt/backupsit

What type of file system is it on Synology side? Has this ever worked?

sudo -u backup sh -c 'echo test > /mnt/backupsit/vm/102/test.tmp && mv /mnt/backupsit/vm/102/test.tmp /mnt/backupsit/vm/102/test'

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox
 
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So, I've doing some test and the folders of the backups aren't being created, I think thats the problem.
If I try to create o rename a folder on that path I can do it, so maybe the problem is with another user that I'm not seeing who it is.

The datastore on the cluster has been added with the user pbs_backups_ it@pbs that is created on the Proxmox backup server and has backup and datastore privileges.

The folder on the synology I think is created with the user backup who is the owner of the datastore created on Proxmox Backup server and is connected via CIFS v3.1.

Can you help me? what can I check?

Thanks a lot!
 
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It sounds like you have a user-mapping issue between Synology and PBS. Or perhaps root folder permission issue. You could open it up to the world as a test: chmod 777 /mnt/backupsit/

My Multiprotocol (NFS/CIFS) file access are long behind me. I can only recommend that you consolidate Linux NAS access to native Linux protocol - NFS.

Familiarize yourself with Synology NFS options (root squash, user mapping, etc). Perhaps, reach out to Synology support, or inquire on their forum. Think of PVE/PBS as a Linux host trying to access an NFS volume - something that has been done for over 30 years now.

Blockbridge : Ultra low latency all-NVME shared storage for Proxmox - https://www.blockbridge.com/proxmox
 
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