Core Issue
The (error) in cmbBackup routine : Permission denied number= 0 error message appears in the backup log when the Cisco Unity Disaster Recovery Tools (DiRT) are used in order to back up the server before rebuild. This happens whether the Administrator, Unityinstall, or UnityAdmin accounts are used.
Resolution
This issue is documented in Cisco bug ID CCSec58822. This issue occurs when an attempt is made to take a DiRT backup to a backup directory that already exists. The problem is related to Enterprise Management System (EMS) file permissions written in the DiRT backup directory. In order to resolve this issue, specify a different backup directory. Then, do the backup.
Refer to Backing Up and Restoring a Cisco Unity System for more information about the DiRT.