Forgive me I am not strong in the Linux. As the title said . Could anyone please tell is there any difference between them? After I look through the help. I didn't found much difference between them. -g, --gid GROUP   The group name or number of the user's initial login group. The group  name must exist. A group number must refer to an already existing  group.-G, --groups GROUP1[,GROUP2,...[,GROUPN]]]    A list of supplementary groups which the user is also a member of.  Each group is separated from the next by a comma, with no intervening  whitespace. The groups are subject to the same restrictions as the  group given with the -g option. The default is for the user to belong  only to the initial group.If they are the same. Why both they exist?Please tell me if I missed something .Many Thanks.
What is the difference between -g and -G options in useradd
linux;permissions;useradd
-g sets the initial, or primary, group. This is what appears in the group field in /etc/passwd. On many distributions the primary group name is the same as the user name.-G sets the supplementary, or additional, groups. These are the groups in /etc/group that list your user account. This might include groups such as sudo, staff, etc.