It’s not unusual that, as your FreeBSD server is so stable, you end not knowing what your password was.

Under other systems the location of webmin is clear and most of the documentation will point you to /usr/libexec/webmin or something like that, in FreeBSD, by default (and after some updates) webmin is installed under

/usr/local/lib/webmin-1.300

Where 1.300 is the running version

And it’s configuration file is located at:

/usr/local/etc/webmin

So, to change the password of let’s say user foo to bar you’ll have to type:

/usr/local/lib/webmin-1.300/changepass.pl /usr/local/etc/webmin foo bar