Make Secondary belongs the both users on sysadmin group.

Do the following steps as:

1.usermod -G sysadmin john

2.usermod –G sysadmin jane

3.Verify by reading /etc/group file

Using usermod command we can make user belongs to different group. There are two types of group one primary and another is secondary. Primary group can be only one but user can belongs to more than one group as secondary.

usermod -g groupname usernameTo change the primary group of the user

usermod -G groupname usernameTo make user belongs to secondary group.