Today I need to change the password of ubuntu18.04, but when I changed the password, the following error occurred:

Authentication token manipulation error

The explanation given online is that there is no authority.
 
The solution

sudo mount -o remount,rw /

Just add a sudo

eric@eric-HP-Z420-Workstation:~$ sudo passwd eric
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

reference
[1]. The modified Linux password times “the Authentication token manipulation error” wrong solution. https://help.aliyun.com/knowledge_detail/41542.html
[2].Fix “Authentication Token Manipulation Error” When Changing User Password In Ubuntu. https://www.codevoila.com/post/26/fix-authentication-token-manipulation-error-when-changing-user-password-in-ubuntu