LOST LINUX PASSWORD?

This is a trick to retrive it

FIRST

Using Knoppix CD http://www.knoppix.net/

take the system offline by removing its ethernet connection and reboot the
system with a knoppix cd in it. remount the HD in read/write mode and edit
the /etc/passwd file. in it you will see the entry for root will read
something like
root:x:0:0:root,,,:/root:/bin/bash

remove the x from between the two :: an save the file. reboot the system and
log in as root, change the password as root now has no password. put system
back online after you have changed the root password to something secure

SECOND

Using GRUB

boot into single-user mode from GRUB, do the following from
the GRUB menu screen:

1. Select the desired kernel.

2. Press the 'e' key to edit that entry.

3. Use the arrow keys to navigate to the kernel line
(for example: kernel /vmlinuz-2.6.x-x ro root=/dev/hdx2)

4. Press the 'e' key to edit the line.

5. Add the argument 'single' to the end of the line and
press return.

6. Press the 'b' key to boot.

7. at promt type passwd

taken from various source