基本命令_创建组/用户

*only root user could use this commad

1 groupadd -g test -- create a group name test

2 usermod -d /home/cici -G test cici

-- change the user cici's login direcotry as  /home/cici and add the user  cici to test group

3 su cici

4 groups -- check the goup for user cici