"John the Ripper is an Open Source password security auditing and password recovery tool available for many operating systems."
Practice until you can't make it wrong.
Practice until you can't make it wrong.
Arch Linux
Removing user postfix from group opendkim
[tuyen@1 ~]$ which gpasswd /usr/bin/gpasswd [tuyen@1 ~]$ gpasswd -d postfix opendkim gpasswd: Permission denied. [tuyen@1 ~]$ sudo gpasswd -d postfix opendkim [sudo] password for tuyen: Removing user postfix from group opendkim [tuyen@1 ~]$