[root@station10-101 ~]# passwd student
Changing password for user student.
New password: <==直接输入 mystdgo 即可！
BAD PASSWORD: The password is shorter than 8 characters
Retype new password: <==再次输入 mystdgo
passwd: all authentication tokens updated successfully.
看吧！ root 很万能，所以，如果耳根子太软，帮人家设计比较不良的密码，很容易出状况！
例题 4.2.1-2：
创建新用户的帐号与密码，两个动作：
[root@station10-101 ~]# useradd myuser2
[root@station10-101 ~]# passwd myuser2
Changing password for user myuser2.
New password:
BAD PASSWORD: The password fails the dictionary check - it is based on a dictionary word
Retype new password:
passwd: all authentication tokens updated successfully.
创建另外一个新的用户，方式也一样：
[root@station10-101 ~]# useradd myuser3
[root@station10-101 ~]# passwd myuser3
Changing password for user myuser3.
New password:
BAD PASSWORD: The password fails the dictionary check - it is based on a dictionary word
Retype new password:
passwd: all authentication tokens updated successfully.
现在，观察一下两个帐号的 id 显示状况：
[root@station10-101 ~]# id myuser2
uid=1001(myuser2) gid=1001(myuser2) groups=1001(myuser2)
[root@station10-101 ~]# id myuser3
uid=1002(myuser3) gid=1002(myuser3) groups=1002(myuser3)
[root@station10-101 ~]# useradd myuser2
useradd: warning: the home directory already exists.
Not copying any file from skel directory into it.
Creating mailbox file: File exists
[root@station10-101 ~]# passwd myuser2
Changing password for user myuser2.
New password:
BAD PASSWORD: The password fails the dictionary check - it is based on a dictionary word
Retype new password:
passwd: all authentication tokens updated successfully.
[root@station10-101 ~]# ll -d /home/myuser* /var/spool/mail/myuser*
drwx------. 3 1001 1001 78 Mar 15 20:53 /home/myuser2
drwx------. 3 myuser3 myuser3 78 Mar 15 20:53 /home/myuser3
-rw-rw----. 1 1001 mail 0 Mar 15 20:53 /var/spool/mail/myuser2
-rw-rw----. 1 myuser3 mail 0 Mar 15 20:53 /var/spool/mail/myuser3
# 文件并没有正常的恢复！看起来 UID/GID 的部份有问题！来查看看：
[root@station10-101 ~]# id myuser2
uid=1003(myuser2) gid=1003(myuser2) groups=1003(myuser2)
[root@station10-101 ~]# userdel -r myuser3<==确实可以删除 myuser3
[root@station10-101 ~]# userdel -r myuser2
userdel: user myuser2 is currently used by process 20486
# 因为刚刚在 tty4 登录 myuser2，尚未注销！赶紧去注销！
[root@station10-101 ~]# userdel -r myuser2
userdel: /var/spool/mail/myuser2 not owned by myuser2, not removing
userdel: /home/myuser2 not owned by myuser2, not removing
# 意思是说，上面的两个文件名并不属于 myuser2，所以自然不能随意删除！
[root@station10-101 ~]# ll -d /home/myuser* /var/spool/mail/myuser*
drwx------. 3 1001 1001 78 Mar 15 20:53 /home/myuser2
-rw-rw----. 1 1001 mail 0 Mar 15 20:53 /var/spool/mail/myuser2
# 确实存在不同的 UID 之故！
[root@station10-101 ~]# id myuser3
id: ‘myuser3’: no such user
[root@station10-101 ~]# id myuser2
id: ‘myuser2’: no such user
# 但是，事实上，这两个帐号确实删除了！
上述的留存的错误文件，只好自己手动移除了！
[root@station10-101 ~]# rm -rf /home/myuser2 /var/spool/mail/myuser2
[root@station10-101 ~]# ll -d /home/myuser* /var/spool/mail/myuser*
ls: cannot access '/home/myuser*': No such file or directory
ls: cannot access '/var/spool/mail/myuser*': No such file or directory
例题 4.2.2-1：
直接使用 usermod 修改次要群组支持时，错误的动作：
[root@station10-101 ~]# id prouser1
uid=1001(prouser1) gid=1002(prouser1) groups=1002(prouser1),1001(progroup)
[root@station10-101 ~]# usermod -G student prouser1
[root@station10-101 ~]# id prouser1
uid=1001(prouser1) gid=1002(prouser1) groups=1002(prouser1),1000(student)
[root@station10-101 ~]# usermod --help
Usage: usermod [options] LOGIN
Options:
......
-G, --groups GROUPS new list of supplementary GROUPS
-a, --append append the user to the supplemental GROUPS
mentioned by the -G option without removing
the user from other groups
......
看起来，说是使用 -a 搭配 -G 的话，会有效的达成我们想要的需求！就是『累加额外的次要群组支持』之意！
使用正确的手段来处理：
[root@station10-101 ~]# id prouser1
uid=1001(prouser1) gid=1002(prouser1) groups=1002(prouser1),1000(student)
[root@station10-101 ~]# usermod -a -G progroup prouser1
[root@station10-101 ~]# id prouser1
uid=1001(prouser1) gid=1002(prouser1) groups=1002(prouser1),1000(student),1001(progroup)
