Ouch !
The only way to reset the root password is through the boot menu.
(press CTRL-C when prompted during the kernel boot)
This is a console operation. Do you have termserver access to the console ?
Given that you can't log in to halt the filer, you'd have to power cycle to re-boot.
You'd want to shut down all hosts using the filer to do this as cleanly as possible.
(or trust in cluster failover when you power cycle the head)
You may do it remotely through the RLM, if you still have the RLM password...
I hope this response has been helpful to you.
At your service,
Eugene E. Kashpureff
ekashp@kashpureff.org
Senior Systems Architect / NetApp Certified Instructor
http://www.linkedin.com/in/eugenekashpureff
(P.S. I appreciate points for helpful or correct answers.)