By default, the backup runs on a live system. If people are using the system, jobs running, etc. files can be modified while tar is backing them up. This generates the error you're seeing in the log. There are two solutions for this. The first is to schedule the backup when the system is idle. However, if LMS is managing a large network, this may not be possible. The other solution is to set BACKUP_OFFLINE=YES in NMSROOT\conf\backup.properties. This will cause the backup script to shutdown all of the LMS daemons prior to backing up the system, then restart them when the backup is done.