debian:~# gpasswd --help
Usage: gpasswd [option] GROUP

  -a, --add USER                add USER to GROUP
  -d, --delete USER             remove USER from GROUP
  -h, --help                    display this help message and exit
  -Q, --root CHROOT_DIR         directory to chroot into
  -r, --remove-password         remove the GROUP's password
  -R, --restrict                restrict access to GROUP to its members
  -M, --members USER,...        set the list of members of GROUP
  -A, --administrators ADMIN,...
                                set the list of administrators for GROUP
Except for the -A and -M options, the options cannot be combined.

例如:将 herald 用户添加到 sudo 组,从而获得使用 sudo 命令的权限。

debian:~# gpasswd -a herald sudo
Adding user herald to group sudo