Renaming SQL Server Instances

Working with virtual machines frequently now I often duplicate entire systems for testing purposes and rename the newly created machine. When SQL Server is included in these images, the new copy is left not knowing what it's own name is.

To tell SQL it has been renamed, you need to run the following.

sp_helpserver
select @@servername
go
 
sp_dropserver 'OLDSNAME'
go
sp_addserver 'NEWNAME','local'
go
 
sp_helpserver
select @@servername
go

Remember you will need to restart the SQL Server service after executing this. You could even do it automatically using this Rename SQL Installation script from back in the day. It will detect the names automatically.