Explore the functions and differences of different user IDs in Linux systems

Linux is an open source operating system with multi-user and multi-tasking features. In the Linux system, each user has a unique user ID (User ID, UID for short) to identify himself. UID is a number used to identify a user. Users can access system resources and execution permissions through UID. This article will explore the functions and differences of different user IDs in Linux systems, and provide specific code examples to illustrate.

1. Super user (root user)

In the Linux system, the super user, the root user, has the highest authority and can access all resources in the system and perform all operations. The UID of the root user is 0, which is a special UID reserved for superusers in Linux systems. Normally, the root user can perform system management tasks, install software, modify configuration files, and other operations.

Sample code:

$ sudo su
Password: （输入密码）
$ id -u
0

2. Ordinary users

In addition to the root user, the Linux system also supports the creation of ordinary users. The UID of ordinary users is usually assigned starting from 1000, and each ordinary user has his own UID. The permissions of ordinary users are restricted by the system administrator, and they cannot perform sensitive operations on the system.

Sample code:

$ id -u testuser
1001

3. System user

In the Linux system, there is also a special type of user, namely the system user. System users are typically used to run system services or programs that do not require logging into the system. The system user's UID is usually less than 1000 and will not appear on the login screen.

Sample code:

$ id -u systemd-resolve
108

4. Switch users

In Linux systems, you can use the su command or sudo command to switch user identities. The su command is used to switch to the account of the specified user, and the sudo command is used to execute the specified command with the permissions of other users.

Sample code:

$ su testuser
Password: （输入密码）
$ id -u
1001

5. Modify user ID

In Linux systems, you can use the chown command to modify the owner of a file or directory, and you can also use the chgrp command. Modify the group to which a file or directory belongs. By modifying the user ID, you can change the owner of a file or directory.

Sample code:

$ chown testuser:testuser testfile.txt
$ ls -l testfile.txt
-rw-r--r-- 1 testuser testuser 0 Apr 21 12:00 testfile.txt

In the Linux system, different user IDs have different functions and differences. The root user has the highest authority and can perform any operation; ordinary users are restricted by authority and can only perform limited operations; system users are usually used to run system services; user permissions and access can be managed by switching users, modifying user IDs, etc. control. An in-depth understanding of the functions and differences of different user IDs is very important for the security and management of Linux systems.

The above is the detailed content of Explore the functions and differences of different user IDs in Linux systems. For more information, please follow other related articles on the PHP Chinese website!