[root@hf-01 ~]# ls /etc/group
/etc/group
[root@hf-01 ~]# head -n4 /etc/group
root:x:0:
bin:x:1:
daemon:x:2:
sys:x:3:
[root@hf-01 ~]# head -n4 /etc/gshadow
root:::
bin:::
daemon:::
sys:::
[root@hf-01 ~]# ls /etc/gshadow
gshadow gshadow-
[root@hf-01 ~]# ls /etc/shadow
shadow shadow-
[root@hf-01 ~]# ls /etc/passwd
passwd passwd-
[root@hf-01 ~]# ls /etc/group
group group-
[root@hf-01 ~]# groupadd grp1
[root@hf-01 ~]# tail -n1 /etc/group
grp1:x:1003:
[root@hf-01 ~]# groupadd -g 1005 grp2
[root@hf-01 ~]# tail -n3 /etc/group
user1:x:1002:
grp1:x:1003:
grp2:x:1005:
[root@hf-01 ~]# groupdel grp1
[root@hf-01 ~]# tail -n2 /etc/group
user1:x:1002:
grp2:x:1005:
[root@hf-01 ~]# groupdel user1
groupdel:不能移除用户“user1”的主组
[root@hf-01 ~]# useradd haha
[root@hf-01 ~]# groupdel haha
groupdel:不能移除用户“haha”的主组