cannot change password: Authentication token manipulation error

[Frédéric]

Hi,

I cannot change the root password:
# LANG=en_US.UTF-8 passwd
Changing password for user root.
New password:
Retype new password:
passwd: Authentication token manipulation error

I tried what is said here:
https://www.tecmint.com/fix-passwd-authentication-token-manipulation-error-i...
without success (I did not find tool pam-auth-update, it's probably ubuntu):
- reboot
- mount -o remount,rw /
- chmod 640 /etc/shadow

Regards,

F