According to this Microsoft documentation site, the master database “records all of the system-level information for a SQL Server system.” This system-level information includes all the user database logins, linked servers, endpoints, and other system-wide configuration settings. Of these, the master database is the most important.

Your configuration may also have an additional one called Configuring Distribution if you have set up database replication, and the server is configured as a replication distributor. There are five main system databases: master, model, msdb, tempdb, and Resource. The system databases are important because they hold important system and database meta-information, without which your SQL Server will not work properly or even start. The SQL Server system databases are system-created and maintained meta-databases that is, they contain data about other databases (in this case, your user-created databases). So should you also back these up? Well, the answer isn’t a simple yes or no … System Databases – What Are They?

But SQL Server also automatically creates and maintains a number of system databases. But by ‘databases’ here, we usually mean your user-created databases. It goes without saying that as a DBA, one of your most important tasks is to schedule and ensure regular backups of your databases.

Sql back up master