How to: Restore the master Database (Transact-SQL)
This topic explains how to restore the master database from a full database backup.
To restore the master database
Start the server instance in single-user mode.
For information about how to specify the single-user startup parameter (-m), see How to: Configure Server Startup Options (SQL Server Configuration Manager).
To restore a full database backup of master, use the following RESTORE DATABASE Transact-SQL statement:
RESTORE DATABASE master FROM <backup_device> WITH REPLACE
The REPLACE option instructs SQL Server to restore the specified database even when a database of the same name already exists. The existing database, if any, is deleted. In single-user mode, we recommend that you enter the RESTORE DATABASE statement in the sqlcmd utility. For more information, see Using the sqlcmd Utility.
After master is restored, the instance of SQL Server shuts down and terminates the sqlcmd process. Before you restart the server instance, remove the single-user startup parameter. For more information, see How to: Configure Server Startup Options (SQL Server Configuration Manager).
Restart the server instance and continue other recovery steps such as restoring other databases, attaching databases, and correcting user mismatches.
The following example restores the master database on the default server instance. The example assumes that the server instance is already running in single-user mode. The example starts sqlcmd and executes a RESTORE DATABASE statement that restores a full database backup of master from a disk device: Z:\SQLServerBackups\master.bak.
For a named instance, the sqlcmd command must specify the -S<ComputerName>\<InstanceName> option.
C:\> sqlcmd 1> RESTORE DATABASE master FROM DISK = 'Z:\SQLServerBackups\master.bak' WITH REPLACE; 2> GO