Reset password of an Linux system

Step 1: Boot into another Linux system

This can be any other Linux system on your computer. It can be another installed distribution, or a live CD such as RIP (Recovery is Possible) or Knoppix.

Step 2: Open a terminal

If you have booted into a system such as Knoppix or the Ubuntu Live CD, you will need to open a terminal first. Alternatively, you can switch to a virtual terminal by pressing CTRL+ALT+F2. You will need root access on this system to gain access to your system.

Step 3: Mount your root filesystem to be rescued

This will be the filesystem that contains your /bin, /etc and /sbin directories, typically /dev/sda1 or /dev/hda1.

Typing the following can give you a list of partitions with sizes, this might give you a clue as to which partition your root partition is:

#cat /proc/partitions

To mount your root partition, type:

#mount /dev/hda1 /mnt  – (Ubuntu Live CD: #sudo mount /dev/hda1 /mnt)

To gain access to your system, type:

#chroot /mnt – (Ubuntu Live CD: #sudo chroot /mnt)

You will now have full access to your old system. To change your root password, type:

#passwd (username if not root – Ubuntu: it’s mandatory to add the username here)

Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

To exit from the chroot, type ‘exit’. You can now reboot (by typing ‘reboot’ and to press enter’) and gain root access to your system again.

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