Just a quick reminder, note-to-self
Linux – Password has been used already. Choose another
root@linux:~ # passwd
Changing password for root.
Reenter New Password:
Password has been used already. Choose another.
Linux is keeping the old password stored on /etc/security/opasswd.
Delete the line containing the user that you’re trying to change the password.
It is encrypted so delete them all or just the last one 😉