Howto recover SQL 2016 cluster instance with bad tempdb path setting? Today I have changed the tempdb's file locations using the ALTER DATABASE MODIFY command and I have accidentaly set it to use the root of the volume. The SQL Server service failed to restart and came up with Access denied errors in eventlog. It is a 2016 Sp1 failover cluster.
I tried to workaround this using 

NET START MSSQL$INST1 /f /T3608


but it does not work.

What can I do about this? How can I restart the service to get able to re-define the setting to use a subfolder.
Pinal Dave wrote up a nice article on how to fix this. Have you tried this?


How to Start SQL Server Service Without tempdb?



  
  NET START MSSQLSERVER /f
  Connect to SQL via SQLCMD
  Run ALTER DATABASE tempdb command
  Restart SQL Server
  


From the looks of things you are having an issue starting SQL that is a named instance. This Microsoft article explains how to use that command with a named instance:


How to: Start an Instance of SQL Server (net Commands)
Start, Stop, Pause, Resume, Restart the Database Engine, SQL Server Agent, or SQL Server Browser Service


Are you getting any errors in the error log for the service startup failure?