Plan rebuilding system databases with Setup when master has no usable backup, then restore logins, jobs, and configuration.
What the model Database Passes to Every New Database
Audit the model database template for recovery model, options, objects, and file size, then verify growth settings on new databases.
Rehearsing a master Database Restore on a Test Instance
Rehearse a master database restore on a matching test instance, including single-user sqlcmd, automatic shutdown, and configuration checks.
SQL SERVER – guest User and MSDB Database – Enable guest User on MSDB Database
I advise disabling the guest user in user databases, but it should stay enabled in the MSDB Database. Here is why, and how to enable it again if it was turned off.
Resource Database Quiz: Where Do the System Objects Live?
This Resource Database Quiz asks where SQL Server stores the definition of sys.objects and whether BACKUP DATABASE can protect it. The answer is the hidden Resource database. A tested script shows its version, its date and the system objects every database sees.