Reset forgotten root password under Linux

Method : 1

You can reset forgotten root password under Linux by booting system into single user mode or emergency mode (also known as rescue mode).

My boot loader is GRUB (see LILO boot loader below)
)Following is the procedure to reset root password if you are using GRUB as a boot loader:

Select the kernel
Press the e key to edit the entry
Select second line (the line starting with the word kernel)
Press the e key to edit kernel entry so that you can append single user mode
Append the letter S (or word Single) to the end of the (kernel) line
Press ENTER key
Now press the b key to boot the Linux kernel into single user mode
At prompt type passwd command to reset password:
You need to mount at least / and other partitions:
# mount -t proc proc /proc
# mount -o remount,rw /

Change the root password, enter:
# passwd

Finally reboot system:
# sync
# reboot


My boot loader is LILO
At LILO boot loader type linux single and press [ENTER] key:
Boot: linux single

When you get the # prompt you will need to type passwd root to reset password:
# passwd

Reboot system:
# sync
# reboot

Method : 2


If you don't have a LiveCD, or the system doesn't have CDROM drive, you can reboot the system into single user mode to reset the password. Simply pass the options "init=/bin/sh" to the kernel from the bootloader menu. When the system boots it will drop you into a root shell. The disk will be mounted read-only so remount it read-write with

mount -o rw,remount /dev/ROOT

(be sure to change ROOT to your actual root partition). Edit /etc/shadow and remove the encrypted password. Reset the root password with passwd and reboot the system.
You should now be able to login with the new password.