$ groups
ubuntu adm dialout cdrom floppy sudo audio dip video plugdev lxd netdev
$ groups tomcat
tomcat : tomcat sudo
대부분 sudo권한이 있는 user가 입력 가능함.
$ sudo gpasswd -a leonkim wheel
Adding user leonkim to group wheel
$ sudo gpasswd -d leonkim wheel
Removing user leonkim from group wheel