User group management commands:
To add a group: groupadd [options] group name
-g GID: Specifies the group ID
Modifying User Groups: groupmod [Options] group name
-g GID: Modify Group ID
-n group name: Modify the group name
groupmod -n qwe asd: asd group of the group name changed to qwe
Delete a user group: groupdel group name
To delete a user group, the user group can not have the initial user exists.
Add the user name to the user group:
gpasswd [Options] group name
Options:
-a Username: the user to the group.
-d Username: the user to delete from the group.
Group added to it, as an additional user groups.