Thanks!
This is how it worked for me:
- On the web UI go to: System / SSH Access and check [x] SSH Access, click “Stop SSH…in 15 min” button. Now the SSH service is active for 15 min.
- Open console, e.g. with PuTTY on Windows
- login as: root
- enter password for root
- type “setup”, press enter, a menu appears.
- navigate to ‘admin’ password and select [OK]
- enter new password twice and select [OK]
Mission accomplished 