Runlevel 3 vs. Runlevel 4

Attribute	Runlevel 3	Runlevel 4
Default runlevel in some Linux distributions	Yes	No
Multi-user mode without GUI	Yes	Yes
Networking services enabled	Yes	Yes
Graphical user interface (GUI) enabled	No	Yes
Used for server environments	Yes	Yes

Introduction

Runlevels are a concept in Unix-like operating systems that define the state of the system and which services are running. Runlevel 3 and Runlevel 4 are two commonly used runlevels, each with its own set of attributes and characteristics. In this article, we will compare the attributes of Runlevel 3 and Runlevel 4 to understand their differences and similarities.

Definition of Runlevel 3

Runlevel 3 is typically known as the multi-user mode with networking enabled. In this runlevel, the system boots into a state where multiple users can log in and use the system simultaneously. It also enables networking services, allowing the system to communicate with other devices on a network. Runlevel 3 is often used in server environments where remote access and network connectivity are essential for operations.

Definition of Runlevel 4

Runlevel 4, on the other hand, is not as commonly used as Runlevel 3. It is often left undefined or used for custom purposes in some Unix-like operating systems. In some distributions, Runlevel 4 may be set up to mimic Runlevel 3 with additional services or configurations. However, the specific attributes of Runlevel 4 can vary depending on the system and its configuration.

Boot Process

When a system boots into Runlevel 3, it initializes all the necessary services and daemons for multi-user operation. This includes starting networking services, file systems, and other essential components for user interaction. Runlevel 3 is designed to provide a stable and functional environment for users to log in and perform tasks on the system.

In contrast, the boot process for Runlevel 4 may differ depending on the system configuration. Since Runlevel 4 is often left undefined or used for custom purposes, the boot process may involve starting specific services or applications based on the system's requirements. This flexibility allows system administrators to tailor Runlevel 4 to meet their specific needs.

Use Cases

Runlevel 3 is commonly used in server environments where remote access and network connectivity are crucial. By enabling networking services, Runlevel 3 allows users to access the system from remote locations and communicate with other devices on the network. This makes it ideal for servers that need to be accessible over a network for various tasks.

On the other hand, Runlevel 4 is often used for custom configurations or specific purposes that do not fit neatly into the predefined runlevels. System administrators may set up Runlevel 4 to start additional services or applications that are not included in other runlevels. This flexibility makes Runlevel 4 a versatile option for customizing the system's behavior.

Service Management

In Runlevel 3, the system starts all the necessary services and daemons for multi-user operation and networking. These services are essential for user interaction and network connectivity, making them crucial for the system's functionality. System administrators can manage these services using tools like systemd or SysVinit to control which services are started or stopped in Runlevel 3.

Similarly, in Runlevel 4, system administrators can manage services and applications to customize the system's behavior. Since Runlevel 4 is often used for custom configurations, administrators have the flexibility to start specific services or applications based on their requirements. This allows for greater control over the system's behavior in Runlevel 4.

Conclusion

In conclusion, Runlevel 3 and Runlevel 4 are two distinct runlevels with their own attributes and use cases. Runlevel 3 is commonly used in server environments for multi-user operation and networking, while Runlevel 4 is often used for custom configurations or specific purposes. Understanding the differences between these runlevels can help system administrators choose the appropriate runlevel for their system's requirements.