reference:https://linhost.info/2013/08/passwd-authentication-token-manipulation-error-ubuntu/
You probably encountered this error while trying to reset the password on a Ubuntu system.
root@u13-04:~# passwd nyuser
Enter new UNIX password: Retype new UNIX password: passwd: Authentication token manipulation error passwd: password unchanged This is the result of trying to work on a file system while mounted as read-only. The solution is a simple one. Before making changes to the users password mount the filesystem as read-write which allows for the necessary changes to be made.
mount -o rw,remount / Now try to change the users passwords again.
root@u13-04:~# passwd nyuser
Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully