Explore the Five Classifications of Linux User IDs

Title: In-depth understanding of the five classifications of Linux user IDs

In the Linux operating system, each user is assigned a unique user ID (User ID) , used to identify and manage user permissions and access levels. The classification of user IDs is very important for system management and permission control. In this article, we will delve into the five classifications of Linux user IDs and give specific code examples.

1. Real User ID (User ID)

The real user ID is the user’s unique identifier in the system and is used to distinguish different users. You can use the following command to view the real user ID of the current user:

$ echo $UID

2. Effective User ID (Effective User ID)

The effective user ID is used to determine the permissions the user has when executing a command. , you can view the effective user ID of the current user through the following command:

$ id -u

3. Saved User ID (Saved User ID)

The saved user ID is used to temporarily switch user permissions, usually in Used when privileged operations need to be performed. You can use the following code to set and restore the saved user ID:

$ sudo -u other_user command 
$ sudo -s 

4. File Owner User ID (File Owner User ID)

The file owner user ID is used to identify the file or directory The owner of the file can use the following command to view the owner user ID of the file:

$ ls -l filename

5. Privileged User ID (Super User ID)

Privileged User ID, also known as the root user (root ), has the highest authority and privileges in the system and can perform system-level operations. You can use the following code to switch to a privileged user:

$ sudo su

Summary: The five classifications of Linux user IDs play a vital role in system management and permission control. By understanding these classifications and corresponding code examples , you can better master the skills and methods of user rights management.

Through the introduction of this article, I believe readers have a deeper understanding of the classification of Linux user IDs. I hope these code examples can help you better manage and control user permissions.

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