Here are some Password-Change related issues in ubuntu linux and their tested solutions:
1.”Authentication token manipulation error“, while trying to change a Ubuntu user’s password:
Possible resaon for this error is that the filesystem night be mounted as read only. To fix it, simply type:
mount -o remount,rw /
2. While using sudo passwd command, it gives “password changed successfully” message., but in reality still taking the same old password, and denying the new password:
To solve this problem, first explicitly switch to the user account whose password you want to change.
sudo su youusername
Tip: you may use sudo whoami command to find the current user.
now try :