LILO >>>
ok, i found the easiest way to change a root passwd on a physically accessed machine is to apply the boot params "init=/bin/bash rw" ie if you use lilo, and your image is "linux" try
press "esc" when lilo prompt comes out, and press "tab"
linux init=/bin/bash rw
this should drop you to a root shell.
use passwd to change the root password and enter your new password.
and run "sync" before you reboot.
finally use ctlr+alt+del for reboot
GRUB >>>
if you use grub, try
(1) At grub boot screen (after restart)
(2) Select the kernel
(3) Press the e key to edit the entry
(4) Select second line (the line starting with the word kernel)
(5) Press the e key to edit kernel entry so that you can append single user mode
(6) Append the letter S (or word Single) to the end of the (kernel) line
(7) Press ENTER key
(8) Now press the b key to boot the Linux kernel into single user mode
(9) When prompted give root password and you be allowed to login into single user mode.
