re. Agent in NetBackup context can relate to a Database plugin for that DBMS backup when the DB is online. So I assume you want to backup only the OS file system
Steps
1. identify the Linux OS and bits you have installed and also the kernel level 2.4 or 2.6, this can be important too.
2. Check its listed in the latest OS Compatibility Matrix for the version of NetBackup you wish to install
3. Go here
How to obtain the installation source download and license keys for NetBackup Server, NetBackup Ent...
Some other URLs
http://seer.entsupport.symantec.com/docs/290620.htm
http://seer.entsupport.symantec.com/docs/315276.htm
