Introduction to Linux run levels: Understand how many run levels there are in Linux

Introduction to Linux run levels: To understand how many run levels there are in Linux, specific code examples are required

In the Linux operating system, the run level (runlevel) refers to the status or mode of the system, which determines which services and processes will run automatically when the system starts. Understanding the runlevels of Linux is very important for system administrators and developers because it can help them manage the startup and running process of the system and make necessary adjustments and optimizations.

There are usually seven running levels in a Linux system, ranging from levels 0 to 6. Each level corresponds to different system status and operations. The following will introduce the meaning and characteristics of each run level one by one, and provide corresponding specific code examples.

Run Level 0: Shutdown
Run Level 0 corresponds to the shutdown state of the system. The system only retains core functions and stops all user processes and services.

init 0

Run Level 1: Single User Mode
Run Level 1 is also called single user mode. The system only starts basic services and does not allow multiple users to log in. It is used for system maintenance and repair.

init 1

Run level 2: Multi-user mode
Run level 2 is multi-user mode. The system starts basic services and network functions, allowing multiple users to log in but without a graphical interface.

init 2

Run Level 3: Command Line Mode
Run Level 3 is also called character mode. The system starts all services but has no graphical interface, which is suitable for server environments.

init 3

Run level 4: Reserved
Run level 4 is a state reserved by the system and will generally not be used.

init 4

Run level 5: Graphical interface mode
Run level 5 is the graphical user interface mode. The system starts all services and graphical interfaces, which is suitable for desktop environments.

init 5

Run level 6: Restart
Run level 6 corresponds to the system restart state. The system will stop all services and restart immediately.

init 6

By understanding the running levels of Linux, we can better control the system startup process and choose the appropriate running level for different needs to improve system performance and security. I hope the content introduced above is helpful to you.

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