PBS Backup Fails/Stalls around 21%-23% on Stopped VM (PVE 9.0.3) Web UI Freeze

kaysho

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Jun 4, 2026
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I'm hitting a consistent roadblock trying to back up a specific 100GB Ubuntu VM (VM 601) to my Proxmox Backup Server. The backup consistently stalls or terminates right around the 21% to 23% mark, which subsequently causes the PBS Web UI to freeze up.

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On the PBS side follow the task log as well as journalctl -f. Also check the system logs for the PVE node.
 
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This is the log from pbs, with the corresponding progress. At this point, the pbs web ui is frozen. I have tried to delete the backup folder multiple times and start afresh, but it still does the same thing.


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Hi, there was a similar report [1], which lead to this bugfix [2]. This is however currently not packaged yet, will be available in proxmox-backup-server with version 4.2.2 or later.

Could you provide a backtrace as described here [3] and attach it here for us to verify this is indeed the same issue?

[1] https://forum.proxmox.com/threads/pbs-stops-working-while-backing-up-vm-at-the-same-point.183705/
[2] https://git.proxmox.com/?p=proxmox-backup.git;a=commit;h=23400016322c7a6981f111558e8d22666e32ee8c
[3] https://forum.proxmox.com/threads/p...ng-up-vm-at-the-same-point.183705/post-853962

Edit: clarify that the backtrace should be attached here, no need to send it via private channels.
 
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I went through the issue raised in [1]. It is the same issue as mine. I have attached the backtrace log.

Edit: I have added the backtrace file as a .txt file.
 

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