格式：username:enable:uid:gid:comment::userdir:usershell

[root@sylixos:/root]# cat /etc/passwd
root:x:0:0:root::/root:/bin/sh
hanhui:x:1:0:admin::/home/hanhui:/bin/sh
anonymous:!:400:400:anonymous::/home/anonymous:/bin/false
[root@sylixos:/root]#