Friday, 8 March 2013

Resetting Linux root password from single user mode

You should have console access to your physical machine such KVM,IPMI..etc.,

At the grub prompt press e to enter edit mode.

Select the second line press e again.

At the end of a similar entry, Your Grub entry will probablly not look the same as this.
kernel /vmlinuz-2.6.18-308.4.1.el5 ro root=/dev/sda3

Add init=/bin/sh (The steps so far should work on Debian/Ubuntu servers although with Ubuntu you might need to use /bin/bash instead of /bin/sh)
kernel /vmlinuz-2.6.18-308.4.1.el5 ro root=/dev/sda3 init=/bin/sh

Now press the enter key and then b to boot.

This will take you into single user mode.

Now mount the root partition in read and write mode so that the changes can be commited.
# mount -o remount,rw /

Once the file system is mounted type the following.
# passwd root
You will prompted for the new password and then to confirm.

Job done reboot.