When GRUB loads up, select the Red Hat Linux entry on the GRUB menu and then press “e” to edit the boot configuration.
Locate a line like this:
kernel /boot/vmlinuz-x.x.xx-x.xxx root=LABEL=/hdc
– type the number ‘1’ at the end.
Doing so boots the computer into run level 1- single user mode you will automatically be logged in as root.
Type ‘passwd’ at the prompt, now you can enter a new password here.