Why would one want to do this? Well I have had to perform this funtion for a number of Unix students who have forgotten their root passwords. Not that I've ever forgotten my root password myself, oh, no, no, no.
Start the FreeBSD system. At the Welcome to FreeBSD! boot menu, press Option 4 to Boot into Single User Mode
When prompted, enter full pathname of your preferred shell or press ENTER for the default /bin/sh
You will be immediately dropped into a single user mode without a root password.
Mount the / file system in read and write mode with the mount
command, by typing the following two commands..
mount -u /
Set up a new password with passwd
Finally reboot the system. Done. Scary eh? Too easy. Makes you think doesn't it! Time to lock that server up somewhere safe..