A, / etc / group file group
more / etc / group file group command to view, the behavior of each user group, four fields represent the following meanings:
1. Create group
groupadd shared: creating a group shared
usermod -G shared test: test the user added to the group shared in
usermod -g shared test: add users to the test group and replace shared user's default group
2. Modify Group
groupmod -n sharing shared: Modify Group shared group called sharing.
3. Delete Group
groupdel sharing: Delete group sharing