Linux系统中useradd、userdel命令

1、linux系统中useradd命令用于创建新的用户

使用方法 useradd name

[root@linuxprobe home]# ls
linuxprobe  software
[root@linuxprobe home]# pwd  ##路径
/home
[root@linuxprobe home]# tail -n 3 /etc/passwd  ## 查看密码信息
tcpdump:x:72:72::/:/sbin/nologin
linuxprobe:x:1000:1000:linuxprobe:/home/linuxprobe:/bin/bash
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
[root@linuxprobe home]# tail -n 3 /etc/group  ## 查看组信息
tcpdump:x:72:
linuxprobe:x:1000:
apache:x:48:
[root@linuxprobe home]# tail -n 3 /etc/shadow  ## 密码信息 ？
tcpdump:!!:18550::::::
linuxprobe:$6$USv3f8Kg8jPgaZXz$7c766cDksJtgc.mdGD1NTVmRZKc/YPu.Y4cziZ3kTkCGznQSUDRapbA.Hs9SbOsIw/453yk9rY.Tzw6rXMvZW1:18550:0:99999:7:::
apache:!!:18551::::::
[root@linuxprobe home]# useradd liujiaxin01  ## 创建普通用户 liujiaxin01
[root@linuxprobe home]# ls  ## 查看效果，多出目录
linuxprobe  liujiaxin01  software
[root@linuxprobe home]# pwd
/home
[root@linuxprobe home]# tail -n 3 /etc/passwd  ## 多出最后一列信息
linuxprobe:x:1000:1000:linuxprobe:/home/linuxprobe:/bin/bash
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin
liujiaxin01:x:1001:1001::/home/liujiaxin01:/bin/bash
[root@linuxprobe home]# tail -n 3 /etc/group  ## 多出最后一列信息
linuxprobe:x:1000:
apache:x:48:
liujiaxin01:x:1001:
[root@linuxprobe home]# tail -n 3 /etc/shadow  ## 多出最后一列信息
linuxprobe:$6$USv3f8Kg8jPgaZXz$7c766cDksJtgc.mdGD1NTVmRZKc/YPu.Y4cziZ3kTkCGznQSUDRapbA.Hs9SbOsIw/453yk9rY.Tzw6rXMvZW1:18550:0:99999:7:::
apache:!!:18551::::::
liujiaxin01:!!:18554:0:99999:7:::
[root@linuxprobe home]# ls -a liujiaxin01/  ## 查看多出目录内隐藏文件
.  ..  .bash_logout  .bash_profile  .bashrc  .mozilla

2、为普通用户创建密码

[root@linuxprobe home]# ls
linuxprobe  liujiaxin01  software
[root@linuxprobe home]# tail -n 3 /etc/shadow  ## 查看密码信息
linuxprobe:$6$USv3f8Kg8jPgaZXz$7c766cDksJtgc.mdGD1NTVmRZKc/YPu.Y4cziZ3kTkCGznQSUDRapbA.Hs9SbOsIw/453yk9rY.Tzw6rXMvZW1:18550:0:99999:7:::
apache:!!:18551::::::
liujiaxin01:!!:18554:0:99999:7:::
[root@linuxprobe home]# echo "123456" | passwd --stdin liujiaxin01  ## 创建初始密码 123456
Changing password for user liujiaxin01.
passwd: all authentication tokens updated successfully.
[root@linuxprobe home]# tail -n 3 /etc/shadow  ## 注意前后变化
linuxprobe:$6$USv3f8Kg8jPgaZXz$7c766cDksJtgc.mdGD1NTVmRZKc/YPu.Y4cziZ3kTkCGznQSUDRapbA.Hs9SbOsIw/453yk9rY.Tzw6rXMvZW1:18550:0:99999:7:::
apache:!!:18551::::::
liujiaxin01:$6$g0Uhd5xO$jh20jT0GTyz3ilrTDKlMdLs713SPLUMnx3CyQzc98brtXd2CCr2ZAAs1Pm6SWKuFKVi6/083E9C0eZq6rRkXg.:18554:0:99999:7:::
[root@linuxprobe home]# read -s -p "input passwd for liujiaxin01:" PASSWD  ## 利用read -s 选项 设置不在屏幕显示密码
input passwd for liujiaxin01:[root@linuxprobe home]#
[root@linuxprobe home]# echo $PASSWD | passwd --stdin liujiaxin01
Changing password for user liujiaxin01.
passwd: all authentication tokens updated successfully.

3、登录测试

login as: liujiaxin01    
liujiaxin01@192.168.3.13's password:
[liujiaxin01@linuxprobe ~]$ whoami  ## 没有问题
liujiaxin01
[liujiaxin01@linuxprobe ~]$

4、普通用户修改密码

[root@linuxprobe home]# ls
linuxprobe  liujiaxin01  software
[root@linuxprobe home]# whoami
root
[root@linuxprobe home]# passwd liujiaxin01  ## root用户修改普通用户密码
Changing password for user liujiaxin01.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: all authentication tokens updated successfully.
[root@linuxprobe home]# su - liujiaxin01
Last login: Mon Oct 19 18:04:04 CST 2020 on pts/0
[liujiaxin01@linuxprobe ~]$ cd /home
[liujiaxin01@linuxprobe home]$ ls
linuxprobe  liujiaxin01  software
[liujiaxin01@linuxprobe home]$ whoami
liujiaxin01
[liujiaxin01@linuxprobe home]$ passwd liujiaxin01
passwd: Only root can specify a user name.
[liujiaxin01@linuxprobe home]$ passwd  ## 普通用户修改密码直接在终端输入 passwd
Changing password for user liujiaxin01.
Changing password for liujiaxin01.
(current) UNIX password:
New password:
Retype new password:
passwd: all authentication tokens updated successfully.

5、只有root用户可以创建和删除用户

[linuxprobe@linuxprobe home]$ ls
linuxprobe  liujiaxin01  software
[linuxprobe@linuxprobe home]$ whoami
linuxprobe
[linuxprobe@linuxprobe home]$ userdel -r liujiaxin01
-bash: /usr/sbin/userdel: Permission denied
[linuxprobe@linuxprobe home]$ useradd liujiaxin02
-bash: /usr/sbin/useradd: Permission denied

[linuxprobe@linuxprobe home]$ su - root
Password:
Last login: Mon Oct 19 18:08:52 CST 2020 on pts/0
[root@linuxprobe ~]# whoami
root
[root@linuxprobe ~]# userdel -r liujiaxin01   ## 有终端使用liujiaxin01登录
userdel: user liujiaxin01 is currently used by process 8699

login as: root
root@192.168.3.13's password:
Last failed login: Mon Oct 19 18:12:44 CST 2020 from 192.168.3.4 on ssh:notty
There was 1 failed login attempt since the last successful login.
Last login: Mon Oct 19 18:12:21 2020 from 192.168.3.4
[root@linuxprobe ~]# userdel -r liujiaxin01
userdel: user liujiaxin01 is currently used by process 8699
[root@linuxprobe ~]# userdel -r liujiaxin01   ## 关闭刘家鑫01登录终端，删除没有问题
[root@linuxprobe ~]# cd /home/
[root@linuxprobe home]# ls
linuxprobe software
[root@linuxprobe home]# tail -n 3 /etc/passwd
tcpdump:x:72:72::/:/sbin/nologin
linuxprobe:x:1000:1000:linuxprobe:/home/linuxprobe:/bin/bash
apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin