Change Root Password Using a Live/Bootable USB

Document Scope

This article provides step-by-step instructions to change the root password if you have forgotten it or are having trouble with it. By following these steps, you should be able to successfully change the root password on your Linux system. 

Prerequisites

This guide assumes the following:

1. You have already created a bootable USB containing a live Linux distribution (such as Ubuntu or Fedora). If you haven't please see the KB article Prepare a Bootable USB.
2. The drive containing the boot partition you want to change the password for is physically installed.
3. You can access the BIOS boot menu to boot from the live USB

Step 1: Create a Directory for Mounting the Target Drive

First, open a terminal window on the live distribution. Once opened, Create a directory to mount the target drive containing the boot partition:

• root@live:~$ mkdir /home/exx/target

Step 2: Locate the Boot Partition of the Target Drive

Identify the boot partition of the target drive using the fdisk -l command (in this example, it would be '/dev/sdb1'):

root@live:~$ fdisk -l
Disk /dev/sda: 32.1 GB, 32094814208 bytes, 62685184 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000a0fa4

Device Boot Start End Blocks Id System
/dev/sda1 * 32 62685183 31342576 c W95 FAT32 (LBA)


Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes, 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0007fbf1

Device Boot Start End Blocks Id System
/dev/sdb1 2048 1026047 512000 83 Linux
/dev/sdb2 1026048 1953523711 976248832 8e Linux LVM

Step 3: Mount the Target Drive Partition

Mount the target drive partition to the directory you just created:

root@live:~$ mount /dev/sdb1 /home/exx/target

Step 4: Change Root to the Mounted File System

Use the chroot command to change root to the mounted file system:

root@live:~$ chroot /home/exx/target

Step 5: Change the Root Password

Use the passwd command to change the root password:

root@live:~$ passwd
Changing password for user root.
New password:

Step 6: Exit the chroot Shell

Exit the chroot shell by typing:

root@live:~$ exit

Step 7: Safely Unmount the Drive

Unmount the drive from the filesystem you created:

root@live:~$ umount /dev/sdb1 /home/exx/target