Introduction to Management Files and User Groups in Linux System

Linux is a multi-user, multi-tasking operating system that understands Linux single-user multi-tasking, multi-user multi-tasking;
User role differentiation:
Users are sub-role in the system. In Linux systems, permissions and tasks are different due to different roles; it is worth noting that the user's role is identified by UID and UID; in system management, The system administrator must adhere to the unique features of UID;
root user: the system is unique, is real, can log in to the system, can operate any file and command, has the highest authority;
virtual user: this type of user also It is called pseudo-user or fake user, and it is distinguished from real users. Such users do not have the ability to log in to the system, but they are indispensable users, such as bin, daemon, adm, ftp. Mail, etc.; such users are owned by the system itself, not by the latter
, However, we can also add virtual users;
Ordinary real users: These users can log in to the system, but can only manipulate the contents of their home directories, and the permissions are limited. These users are added by the system administrators themselves;
If you want to know some accounts of Linux system, please check /etc/passwd ;
The correspondence between users and user groups is: one-to-one, many-to-one, one-to-many or many-to-many;
with users (user) and user group (group) related configuration files:
1) User (user) related configuration files;
Code is as follows:
/etc/passwd
Note: User (user The configuration file;
The code is as follows:
/etc/shadow
Note: User (user) shadow password file;
2) Configuration file related to user group;
The code is as follows:
/etc/group
Note: User group (group) configuration file;
Code is as follows:
/etc/gshadow
Note: User group (group) shadow file;
Manage tools and commands for users and groups:
1, management user (user) tools or commands;
useradd Note: add users;
adduser Note: add users;
passwd Note: set passwords for users;
usermod Note: Modify the user command, you can use the usermod to modify the login name, the user's home directory, and so on;