About external access to NetBackup controlled devices on UNIX
On UNIX hosts, the NetBackup Device Manager restricts access to drives that are in an UP state by changing the permissions of the device files for those drives. The Device Manager changes the permissions to 0600 when it starts and back to their original settings when it is terminated. The permissions also are returned to their original settings when a drive's state is changed to DOWN.
See About the NetBackup Device Manager.
Do not modify the permissions of these device files when the Device Manager is active. The automatic volume recognition process (avrd) periodically tries to rewind and read data from media in the drives that are UP and are not currently assigned in NetBackup.
To ensure reliable operation, do not use UNIX tape and drive commands on the drives that are UP and controlled by the Device Manager. Users can use the NetBackup tpreq and tpunmount commands and the drive_mount_notify and drive_unmount_notify scripts on those drives.
See "NetBackup notify scripts" in the NetBackup Administrator's Guide, Volume II