Authentication token manipulation error

One of my friend forgot his ubuntu password and i tried to fix it by going to recovery mode dropping into root shell and resetting the password for the user

root@username-PC:~# passwd username
Enter new UNIX password:
Retype new UNIX password:
passwd: Authentication token manipulation error
passwd: password unchanged

But this time it didn’t work as usual. It showed an error “Authentication token manipulation error”.
I tried googling an found that the file system is not mounted with read/write permission.
From root shell remount file system with read/write permission.

mount -rw -o remount /

Then try changing the password using

passwd username

Some times it may may throw the same error again, then delete the password for the user from /etc/shadow file using the fllowing command

sudo passwd -d username

Replace username with your’s. Then again change the password using

passwd username

Happy Hacking 🙂