In-depth discussion: The role and characteristics of Linux run levels

Introduction

Linux is an open source operating system that is widely used in servers and embedded systems. In Linux systems, runlevel (runlevel) is an important concept, which defines the operating mode of the system in different states. Each runlevel corresponds to a specific set of services and functions.

The role of run level

The run level in the Linux system is mainly used to control the startup configuration and usage of the system in different states. By switching the run level, the system can be restarted, shut down, Single user mode and other features. Different run levels determine the services that are loaded and the processes that run when the system starts. You can choose the appropriate run level according to your needs.

Characteristics of run levels

Seven run levels: There are generally seven run levels in a Linux system, namely 0-6. Each runlevel defines the services and processes that are loaded when the system starts.
Default running level: Normally, the default running level of the Linux system is 3. At this level, the system will start most services, which is suitable for servers and other situations that require network functions.
Switch running level: You can switch the running level through the command line or graphical interface. Different distributions may be slightly different. Generally, you can use the init command or systemctl command to switch run levels.
The difference between each run level: Different run levels correspond to different services and processes. For example, a run level of 1 indicates single-user mode. Only the most basic services are loaded, which is suitable for the system. Fault repair, etc.

Code example

The following takes the Ubuntu system as an example to demonstrate how to switch the run level:

View the current run level
```
runlevel
```
Copy after login
Switch to single-user mode
```
sudo init 1
```
Copy after login
Switch to multi-user text mode
```
sudo init 3
```
Copy after login
Switch to graphical interface Pattern
```
sudo init 5
```
Copy after login

Summary

Through the above introduction and code examples, we have a deeper understanding of the run levels in the Linux system. Understanding the functions and characteristics of different run levels can help us better manage and configure Linux systems and improve the flexibility and stability of the system. I hope this article can be helpful to readers, and welcome discussions and additions.

Reference materials

Detailed explanation of Linux run level: https://blog.csdn.net/wpuwpu987/article/details/6047035
Linux run level switching: https://www.cnblogs.com/mctr/articles/1323979.html

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