Error in Comet Backup: Couldn't take snapshot (VSS Warning: An imminent failure indicates either bad privileges or WOW64.)

Kuzma Ivanov
Updated

Symptoms

When running a backup job that uses VSS, the backup fails, and Comet Backup reports an error similar to:

VSS Error: Couldn't take snapshot (VSS Warning: An imminent failure indicates either bad privileges or WOW64.)

Cause

This warning originates from Microsoft's VSS subsystem and usually indicates insufficient privileges.

  • The Comet Backup delegate service is not running under an account with the required administrative permissions.
  • On a server that is joined to an Active Directory domain, a domain-level Group Policy Object (GPO) can override or strip the privileges required to take a VSS snapshot, even when those privileges are set correctly on the local machine.

Resolution

Solution 1
  1. Open the Windows services menu on the affected endpoint (run services.msc)
  2. Locate backup.delegate or Brandname (delegate service) in the list.
  3. Open the service properties.
  4. Switch the "logon as" value to Local System.
Local System.jpg
Solution 2

Keep the delegate service running as the backup.delegate account, and ensure it has the required permissions.

  1. Confirm that backup.delegate is a member of the Backup Operators local group.
  2. Ensure the account holds the following privileges: 
    • SeBackupPrivilege, 
    • SeRestorePrivilege, 
    • SeShutdownPrivilege, 
    • SeChangeNotifyPrivilege, 
    • SeServiceLogonRight, and 
    • SeCreateSymbolicLinkPrivilege.
  3. If the server is joined to an Active Directory domain, check the local and domain Group Policy for User Rights Assignment settings that remove these privileges from backup.delegate, and add an exception or adjust the policy accordingly.
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