Most SMS/ConfigMgr administrators are aware of the importance of backing up the ConfigMgr database itself. The recommended approach, is configuring the SMS/ConfigMgr backup task to run on a pre-defined schedule.
However, SQL Server has system databases which are not backed up by the backup task process mentioned above. SQL Server System databases include; master, msdb, model and tempdb. Of these, master and msdb should be backed up.
At a minimum, I recommend setting a scheduled system database backup for Master and MSDB, as this will give you additional options in the event you need to perform an SQL Server recovery.
What are the SQL Server system databases? Here are their descriptions (from MSDN)
System databases
Description
master Database
Records all the system-level information for an instance of SQL Server.
msdb Database
Is used by SQL Server Agent for scheduling alerts and jobs.
model Database
Is used as the template for all databases created on the instance of SQL Server. Modifications made to the model database, such as database size, collation, recovery model, and other database options, are applied to any databases created afterward.
Resource Database
Is a read-only database that contains system objects that are included with SQL Server. System objects are physically persisted in the Resource database, but they logically appear in the sys schema of every database.
tempdb Database
Is a workspace for holding temporary objects or intermediate result sets.
Use the Maintenance Plan Wizard to perform the system database backups. Steps are described here, here and finally.
Select the Master and MSDB databases, usually 1x/week is sufficient for a schedule, keeping the last 4 backups. Be sure to back these up to tape or disk!