Linux user classification and user management

User classification UID explain
administrators 0 All permissions
Program user 1-999 It is not allowed to log in to the system when running specific programs or services
Ordinary users 1000-60000 Created by the administrator, you can log in to the system to manage and maintain the system

The user’s attribute information includes but is not limited to: home directory, unique identity (uid), belonging group (GID), etc.

#Create user, must be unique
useradd yunwei

#View created users
id yunwei

#Switch user identity
su yunwei
ls -al
#View the shell parsers supported by the system
cat /etc/shell

#Create a user and specify the nologin parser, that is, it is not allowed to log in to the system
useradd -s /sbin/nologin test
#Change the password of the specified user
passwd yunwei

#Modify the password of the currently logged in user

#Set the password through script without interactive setting
echo 12345678|passwd --stdin yunwei1
#Save file of user basic information
vim /etc/passwd

#Save file of user password information
vim /etc/shadow
Name: encrypted password: offset date of the last password modification: minimum password modification interval: how many days must the password be modified: reminder period of password modification warning: grace period of password modification: account expiration date: reserved field
#Displays information related to the user's account date
chage -l yunwei

#The password must be changed when setting user login
chage -d 0 yunwei

#Set user expiration in 30 days
date -d '+30days' +%F
chage -E $(date -d '+30days' +%F) yunwei
#Modify the user's shell information
usermod -s /bin/sh test

#Modify and migrate the user's home directory information
usermod -md /home/test1 test1
#Delete users only
userdel test

#Delete information such as user and home directory
userdel -r test

#Delete the logged in user
userdel -f test1

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