To recover ASA password where password is not known:

1. Connect to the ASA console port
2. Power off the ASA, and then power it on.

After start-up, press the Escape key when you are prompted to enter ROMMON
mode.

To update the configuration register value, Enter the following command:

rommon #1> confreg 0x41

To boot with fresh config:

rommon #2> boot