NeXt Cube

From http://www.bangmoney.org/nextstep/root_password.html

Lost Root Password

If you've forgotten the root password, you'll need to follow the following procedure to reset it so you can login as root. This is most helpful to people who've just purchased a used NeXT but don't know what the root password is.

Reboot the system.
Immdeiately after the "Testing System" message is replaced with "Loading from disk", hold down the right command key and press the tilde (~) on the numeric keypad. You are now at the ROM monitor.
Boot the machine into single user mode. Most people boot off the hard disk, and should type the following at the ROM monitor prompt:
NeXT> bsd -s
Once the system has started and dumps you at a root prompt, you need to make sure NetInfo and other services get started. Do this by typing:
# sh /etc/rc &
Set the root password using:
# passwd root
Now, reboot the system and you can use the new password.