User and group management

One 、 User management ​

The user types :

• Super administrator root
• Ordinary users
• System users
  • Ensure that the application can be used normally 、 function
  • It is not allowed to log in to the system , There is security

User related files

1、/etc/passwd

Save user information

root:x:0:0:root:/root:/bin/bash
 Format :   user name : Password placeholder :uid:gid: explain : Home directory :shell

uid  user ID 

	 Administrators   0
     System users 	1----999
	 Ordinary users 	1000+
	
shell   to Linux Kernel translation commands 
	
	/bin/bash
		 Default shell,  You can log in to the system normally 、 Carry out orders 
	/sbin/nologin
		 You are not allowed to log in to the system 

2、/etc/shadow file

Save the user's password

Two 、 User management operations

1、 Create user

useradd  [ Options ]   user name 
[[email protected] ~]# useradd user01

Common options ：

 -u   Designated user ID
[[email protected] ~]# useradd -u 2022 user02

 -s       Specify the user's shell

 -M		 Do not create the user's home directory 

[[email protected] ~]# useradd -s /sbin/nologin -M nginx

[[email protected] ~]# useradd -u 2001 -s /sbin/nologin -M tomcat

 -g  Basic group  

[[email protected] ~]# groupadd group1
[[email protected] ~]# useradd -g group1 apache

 -G  Additional group , Additional group , Additional group 

[[email protected] ~]# groupadd nginx
[[email protected] ~]# groupadd httpd
[[email protected] ~]# groupadd tomcat
[[email protected] ~]# 
[[email protected] ~]# useradd -G nginx,httpd,tomcat  apache      // Multiple additional groups are separated by commas 

2、 Switching users

su -  user name  

[[email protected] ~]# su - apache

3、 Set user password

passwd [ Options ] [ user name ]

 
[[email protected] ~]# passwd 		// Change the current user password 
Changing password for user root.
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.

// Change the password of the specified user ,  Only administrators root Can be successfully executed  
[[email protected] ~]# passwd user01

 -l    Lock user password , Can't log in to the system 
[[email protected] ~]# passwd -l user01
Locking password for user user01.
passwd: Success

 -u    Unlock user password  
[[email protected] ~]# passwd -u user01
Unlocking password for user user01.
passwd: Success

 -e   Force user password expiration , You have to change your password the next time you log in 

[[email protected] ~]# passwd -e user01
Expiring password for user user01.
passwd: Success

4、 To view the user ID Information

[[email protected] ~]# id apache

5、 Modify user information

 usermod [ Options ]  user name  

-u    Modify the user ID 

[[email protected] ~]# id userA
uid=1003(userA) gid=1003(userA) groups=1003(userA)
[[email protected] ~]# 
[[email protected] ~]# usermod -u 3000 userA

[[email protected] ~]# id userA
uid=3000(userA) gid=1003(userA) groups=1003(userA)


-s     Modify the user shell 

[[email protected] ~]# grep "userB" /etc/passwd
userB:x:1004:1004::/home/userB:/bin/bash

[[email protected] ~]# usermod -s /sbin/nologin userB
 
[[email protected] ~]# grep "userB" /etc/passwd
userB:x:1004:1004::/home/userB:/sbin/nologin


-G  Additional group ,  Additional group       Add users to additional groups  

[[email protected] ~]# id userC
uid=2000(userC) gid=2000(userC) groups=2000(userC)

[[email protected] ~]# groupadd caiwu
[[email protected] ~]# usermod -G caiwu userC

[[email protected] ~]# id userC
uid=2000(userC) gid=2000(userC) groups=2000(userC),2008(caiwu)

[[email protected] ~]# usermod -aG caiwu userC			//-a The parameter is to keep the current group of the user , Add a new group 
[[email protected] ~]# id userC
uid=2000(userC) gid=2000(userC) groups=2000(userC),2008(caiwu),2009(jishu)

-L   Lock user password  
-U   Unlock user password 

6、 Delete user

 userdel [ Options ]   user name  

-r    Delete user's home directory 

[[email protected] ~]# userdel -r userA

7、 View user login information

[[email protected] ~]# who 
root     pts/0        2020-12-17 17:09 (192.168.183.1)
root     pts/1        2020-12-17 18:00 (192.168.183.1)
user01      :2           2020-12-17 19:35 (:2)

8、 View failed logins

[[email protected] ~]# lastb 

9、 View all login behaviors

[[email protected] ~]# last

3、 ... and 、 User group management operations

User group related files :

/etc/group

1、 Create user group

groupadd   Group name  

2、 Delete user group

groupdel   Group name 

3、 Remove user from group

gpasswd [ Options ]  user   Group name 

[[email protected] ~]# gpasswd -d apache tomcat
Removing user user01 from group tomcat

Four 、 User related profiles

Every time a user is created , The system will automatically /etc/skel Copy the files of the directory to the user's home directory

[[email protected] ~]# ls -a /home/user06/
.  ..  .bash_logout  .bash_profile  .bashrc

1、 .bash_profile Define environment variables

The commands in this file , It will be automatically executed when the user logs in to the system

[[email protected] ~]# vim /home/user01/.bash_profile 
	echo ' Automatic execution ！'

[[email protected] ~]# su - user01
Last login: Thu Dec 17 23:02:59 CST 2020 on pts/6
 Automatic execution ！
[[email protected] ~]$ exit

Global file /etc/profile

Effective for all users in the system

2、 .bashrc Define command aliases

The command of this file , It will be automatically executed when the user opens a new terminal

Global file /etc/bashrc

// See aliases 
[[email protected] ~]# alias 


 To delete an alias  
[[email protected] ~]# unalias cs 


 For the user user01 Define command aliases  
[[email protected] ~]# vim /home/user01/.bashrc 
alias lc='ls -ldh /etc/'

[[email protected] ~]# su - user01
Last login: Thu Dec 17 23:07:23 CST 2020 on pts/5
 Automatic execution !

[[email protected] ~]$ lc
drwxr-xr-x. 142 root root 8.0K Dec 17 23:15 /etc/

3、 .bash_history

After the user logs in to the system , Will appear , Record the historical commands executed by the corresponding user

history   // View history command 

history -c // Clear history command 

Four 、 Reset root password

1、 Restart the system

2、 Boot to grub Menu interface , Press up and down , Pause start

3、 choice gruab The first item in the menu , By letter e Edit the system startup configuration file

4、 find linux16 Beginning line , Add... At the end of the line rd.break

5、 Press ctrl + x Start again , Enter rescue mode

6、 Remount the root directory by reading and writing

switch_root# mount -o rw,remount  /sysroot

7、 Switch to the rescue mode root directory

switch_root# chroot /sysroot

8、 Use passwd Command reset password

sh-4.2# passwd root  

9、 Create hidden files

sh-4.2# touch /.autorelabel

10、 Knock twice exit Exit rescue mode , The system will start normally