master database contains server-wide information about the SQL Server system. This server-wide information includes logins, linked server information, configuration information for the server, and information about user databases created in the SQL Server instance. The actual locations of the database files and key properties that relate to each user database are stored in the
SQL Server cannot start without a
master database. This is not surprising, given the type of information it contains. Without the
master database, SQL Server does not know the location of the databases it services and does not know how the server is configured to run.