Unable to acquire lock "/etc/proxmox-backup/.datastore.lck"

I

idoc_sys

New Member
Jan 8, 2026
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Hello there!
Started getting such error on both datastores "unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - interrupted system call (os error 4)"

I have already checked the user and the group, checked how datastores mounted to server. Tried to stop proxmox-backup and proxmox-backup-proxy processes and delete .datastore.lck file. Didn't help. Upgraded to version "proxmox-backup-server 3.4.8-1 running version: 3.4.8"

Any ideas how to fix?
 
Hi,
did you check that there is no lingering PBS task which might still hold the datastore lock. Maybe stop the PBS systemd services and check the output of ps auwx | grep proxmox-backup
 
Chris said:
Hi,
did you check that there is no lingering PBS task which might still hold the datastore lock. Maybe stop the PBS systemd services and check the output of ps auwx | grep proxmox-backup
Click to expand...
Seems nothing
root@pvebackup:~# systemctl stop proxmox-backup.service proxmox-backup-proxy.service
root@pvebackup:~# ps auwx | grep proxmox-backup
root 10866 0.0 0.0 6332 1600 pts/0 S+ 15:08 0:00 grep proxmox-backup
 
How frequent are the locking errors? Do you see a lot of api requests which might lead to lock contention?
 
Yes, it looks like
Jan 08 15:01:10 pvebackup proxmox-backup-proxy[2087]: lookup_datastore failed - Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - Interrupted system call (os error 4)
Jan 08 15:01:20 pvebackup proxmox-backup-proxy[2087]: lookup_datastore failed - Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - Interrupted system call (os error 4)
Jan 08 15:01:30 pvebackup proxmox-backup-proxy[2087]: lookup_datastore failed - Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - Interrupted system call (os error 4)
Jan 08 15:01:40 pvebackup proxmox-backup-proxy[2087]: unable to start datastore prune job s-e66c92c1-a661 - Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - Interrupted system call (os error 4)
Jan 08 15:01:50 pvebackup proxmox-backup-proxy[2087]: unable to start datastore verification job v-56b0ba95-8500 - Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - Interrupted system call (os error 4)
Jan 08 15:02:08 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:60116] Device or resource busy (os error 16)
Jan 08 15:02:18 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:50978] Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - I>
Jan 08 15:02:29 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:39794] Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - I>
Jan 08 15:02:39 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:33022] Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - I>
Jan 08 15:02:50 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:36456] Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - I>
Jan 08 15:03:00 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:37930] Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - I>
Jan 08 15:03:10 pvebackup proxmox-backup-proxy[2087]: GET /api2/json/admin/datastore/storagebox/status: 400 Bad Request: [client [::ffff:IP]:39928] Unable to acquire lock "/etc/proxmox-backup/.datastore.lck" - I>

And frozen storage
Screenshot 2026-01-08 171251.png
 
Please post the output of ls -la /etc/proxmox-backup/ and fuser /etc/proxmox-backup/.datastore.lck. What PBS version was running previous to the upgrade?
 
is this datastore backed by a hetzner storagebox?
 
its performance and reliablity are not on a level where I would consider using it directly as a datastore. the lock failures are likely (transient?) issues on their end, either ratelimiting or service interruptions.
 
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