Windows Client Error Hyper-V: "At this time nothing can be backed up" (Service hangs completely)

client
1

Hi everyone,

I am facing a critical issue with my UrBackup Windows client. The client’s GUI displays the following error message:

[Window Title] UrBackup [Content] There is an error. At this time nothing can be backed up.

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The main issue is that whenever this error occurs, the UrBackup background service on Windows completely stops/crashes. It aborts all operations and does not attempt to run again, leaving the entire backup routine paralyzed until the service is manually restarted.

We are currently deploying the UrBackup Hyper-V module on this server, which hosts about 10 Hyper-V VMs. For context on hardware resources, the host server currently has about 32GB of free RAM available, so it shouldn’t be running out of physical memory.

Does anyone know what might be causing the background service to completely halt while displaying this message on the frontend? Is there any configuration or workaround to prevent the service from simply “dying” when VSS or network failures occur?

Instead of attaching the full file, here is the relevant snippet from the debug.log where the fatal exceptions (Application Crashed / SIGABRT / bad allocation) happen:

2026-05-08 10:41:15: ClientService cmd: STATUS DETAIL#pw=[REDACTED]
2026-05-08 10:41:16: ClientService cmd: STATUS DETAIL#pw=[REDACTED]
2026-05-08 10:41:16: ClientService cmd: STATUS#pw=[REDACTED]
2026-05-08 10:41:16: WARNING: No reference point found. Resetting CBT
2026-05-08 10:41:16: Hyper-V save_id 12
2026-05-08 10:41:16: Script “C:\Program Files\UrBackup\preimagebackup.bat” does not exist
2026-05-08 10:41:16: Creating shadowcopy of “hyperv://[VM-NOME]/SCSI:0:0”…
2026-05-08 10:41:16: ERROR: Thread exit with unhandled std::exception bad allocation
2026-05-08 10:41:16: ERROR: Fatal exception code 3765269347 at address 0x00007FFD063EA80A
2026-05-08 10:41:17: ERROR: Fatal exception (APPLICATION CRASHED). Crash dump written to “C:\Windows\TEMP\UrBackup\v2.0.0-20260508-104116-18992-28916.dmp”
2026-05-08 10:41:17: ERROR: Program abort (SIGABRT)
2026-05-08 10:41:17: ClientService cmd: STATUS DETAIL#pw=[REDACTED]
2026-05-08 10:41:18: ClientService cmd: STATUS DETAIL#pw=[REDACTED]

Another instance:

2026-05-08 10:30:29: rc=0 hasError=true state=0
2026-05-08 10:30:29: SERVICE_COMMANDS finished
2026-05-08 10:30:29: Started connection to SERVICE_COMMANDS
2026-05-08 10:30:29: ClientService cmd: #[REDACTED]#INCRINTERVALL “259203?startup_delay=120”
2026-05-08 10:30:29: rc=0 hasError=true state=0
2026-05-08 10:30:29: SERVICE_COMMANDS finished
2026-05-08 10:30:29: WARNING: No reference point found. Resetting CBT
2026-05-08 10:30:29: Hyper-V save_id 7
2026-05-08 10:30:29: Script “C:\Program Files\UrBackup\preimagebackup.bat” does not exist
2026-05-08 10:30:29: Creating shadowcopy of “hyperv://[VM-NOME]/SCSI:0:0”…
2026-05-08 10:30:29: ERROR: Fatal exception code 3221225477 at address 0x00007FFC81861500
2026-05-08 10:30:29: Started connection to SERVICE_COMMANDS
2026-05-08 10:30:29: ClientService cmd: #[REDACTED]#CAPA clientsubname=[VM-NOME]
2026-05-08 10:30:29: ERROR: Fatal exception (APPLICATION CRASHED). Crash dump written to “C:\Windows\TEMP\UrBackup\v2.0.0-20260508-103029-34944-14856.dmp”
2026-05-08 10:30:29: ERROR: Program abort (SIGABRT)

2

Sorry you are having this issue. Could you send me the zipped dump file. E.g. at bugreports@urbackup.org . I can also give you a location to upload it if required.

3

Just sent the .dmp files via email to bugreports@urbackup.org. Thanks for the support!

4

Thanks for sending the dump file.

Could you send me the log file as well?

If it has a log line like Did not find select hard disk [...] in it than that is the cause of the issue.

5

is Windows Server 2025 with April 2025 CU installed ?

6

Thank you for the reply. I have just sent the requested log files to your email. I will also look out for the “Did not find select hard disk” line you mentioned.

However, today I am facing an additional problem. I am trying to back up a 1TB VM, and the backup starts normally but stops right in the middle of the process, returning an “Opening filesystem on device failed” error. I have already verified our storage repository, and we definitely have plenty of free space available for this backup.

Here is the log snippet for this new error:

2026-05-11 08:04:59: ClientService cmd:Starting unscheduled full image backup of volume “SCSI:0:0”…
0-1778493577-Basing image backup on last incremental or full image backup
1-1778493577-Error retrieving last image backup. Doing full image backup instead.
0-1778493577-Loading ZIP metadata from urbackup/mbr_data_sissv-rds01–SCSI_0_0.zip
0-1778493577-sissh-hv02[sissv-rds01]: Loading MBR zip file…
0-1778493600-sissh-hv02[sissv-rds01]: Loaded MBR zip file (10.2305 KB)
2-1778497477-Error on client occurred: Opening filesystem on device failed. Stopping.
0-1778497507-Time taken for backing up client sissh-hv02[sissv-rds01]: 1h 5m 30s
2-1778497507-Backup failed

Could you please take a look at this as well? Let me know if the logs I emailed help clarify both issues.

Best regards

7

It wasn’t updated, but I have just applied the April 2025 Cumulative Update. Have you come across anything similar or seen this issue happen before?