1. Introduction

The kernel is the core component of an operating system that manages hardware resources and provides essential services to applications. In the world of operating systems, there are different types of kernels, each with distinct design philosophies and use cases. Here are the main types of kernels:

Types of Kernel

1. Monolithic Kernel

In a monolithic kernel, the entire operating system runs in supervisor (kernel) mode. All basic services such as process management, memory management, file systems, and device drivers are part of a single large kernel binary.
This design offers high performance due to minimal context switches between kernel components but can become complex and harder to maintain.

Examples:

• Linux Kernel
• UNIX (traditional systems like BSD)

2. Microkernel

A microkernel keeps only essential functions such as inter-process communication (IPC), basic scheduling, and minimal memory management in the kernel space. Other services like drivers, file systems, and networking run in user space as separate processes (servers or daemons).

Examples:

• MINIX
• QNX
• L4 Microkernel Family

3. Hybrid Kernel

A hybrid kernel combines elements of both monolithic and microkernel designs. It tries to offer the modularity and reliability of microkernels while maintaining the performance benefits of monolithic kernels by allowing some services (like device drivers) to run in kernel space.

Examples:

• Windows NT family (Windows XP, 7, 10)
• macOS (XNU Kernel)

4. Exokernel

An exokernel is an experimental kernel architecture that aims to provide minimal abstractions, allowing applications more direct control over hardware resources. The kernel only handles resource allocation and protection, leaving most functionalities to user-space libraries.

Examples:

• MIT Exokernel Project

What is the Linux Kernel?

The Linux kernel is a monolithic kernel that forms the core of the Linux operating system. It is responsible for managing hardware, system resources, and providing essential services for user-space applications.

Originally created by Linus Torvalds in 1991, the Linux kernel has since become one of the most widely used and actively developed kernels in the world, powering everything from smartphones to supercomputers.

Linux Kernel Versions

Linux follows a versioning format: Major.Minor.Patch

For example:
6.9.1

• 6 → Major version
• 9 → Minor version (new features/improvements)
• 1 → Bug fixes/security patches.

You can check your Linux kernel version by running:

uname -r

Main Roles of the Linux Kernel

• Process Management
  Handles creation, scheduling, and termination of processes.

• Memory Management
  Manages RAM, virtual memory, and swap space.

• Device Management
  Controls device drivers and hardware access.

• File System Management
  Manages data storage, file operations, and permissions.

• Network Management
  Handles networking protocols, sockets, and data transmission.

• Security & Access Control
  Enforces permissions, authentication, and security policies.

• System Calls Interface
  Provides system call APIs for user programs to access kernel services.