Quick steps to restore the SQL Server system database – msdb from a valid backup file, especially useful if you run SSIS packages stored in the msdb database and SQL server agent jobs. Doing this will bring back all SSIS packages as well as existing job schedules.
– Set msdb database to restricted access
ALTER DATABASE [msdb] SET RESTRICTED_USER WITH ROLLBACK IMMEDIATE
– shut down the SQL server agent service for the SQL instance you are running
– restore the msdb database from a good backup file
– restart the SQL server agent service