I have received following questions many times. I will list all the questions here and answer them together.
What is the purpose of Master database?
Should we backup Master database?
Which database is must have database for SQL Server for startup?
Which are the default system database created when SQL Server 2005 is installed for first time?
What happens if Master database is corrupted?
Answers to all of the questions are very much related. Master database is system database and it contains information about running server’s configuration. When SQL Server 2005 is installed it usually creates master, model, msdb, tempdb resource and distribution (last two depends on version of SQL Server) system database by default. Only Master database is the one which is absolutely must have database. Without Master database SQL Server can not be started. This is the reason it is extremely important to backup Master database.
If Master database is corrupted it should be restored from the latest backup, considering SQL Server was able to start with damaged Master database. Sometimes Master database is corrupted so much it can not start SQL Server at all and it can not be restored. SQL Server should be rebuild using command prompt and restored from latest backup once again.
I am very much interested to know the feedback of readers who have asked questions regarding this issues.
Reference : Pinal Dave (http://blog.SQLAuthority.com)