Recover SQL Server 'sa' password

recover_sa_pwd

#1 Change the DB to single-user mode;
e.g. in SQL Configuration Manager, SQL Server services / <Your Server> / Properties / Startup Parameters
-f (Add, Apply)
RESTART (or stop, start)

#2
C:\Users\Administrator>SQLCMD -H $localhost
1> CREATE LOGIN newSA WITH PASSWORD = 'Pass@123'
2> go
1> ALTER SERVER ROLE sysadmin ADD MEMBER newSA
2> go


#3 change to multi-user mode (i.e. remove -f parameter) 
RESTART (or stop, start)

Then, you should be able to login as newSA in SSMS, and reset the pwd for 'sa'