If you enable SSH access on the controller, just access it using terminal console.
Or do as cjoseph says, using serial.
For reset procedure :
- Login
- Enable
# write erase
# write erase all
# reload
Issuing the write erase command on a controller running software licenses does not affect the license key
management database on the controller.
Issuing the write erase all command resets the controller to factory defaults, and deletes all databases on
the controller including the license key management database. You must reinstall all previously-installed
license keys.