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Chapter 1.4 - High-Level Architecture

Learning Objectives​

By the end of this chapter, you will be able to:

  • Understand the structure of a Linux system
  • Identify the components of the Kernel
  • Identify the components of User Space
  • Understand the communication between components

Introduction​

A Linux system is organized into multiple layers that work together. Understanding this architecture is essential for mastering Linux.

System Overview​

Basic Structure​

Two main spaces:

  1. User Space: Applications and user programs
  2. Kernel Space: System and hardware management

User Space​

Applications​

Programs you use:

  • Web browsers
  • Text editors
  • Development tools
  • Games, etc.

Shell​

Command line interface:

  • Bash: Default shell on most distributions
  • Zsh: Modern and powerful shell
  • Fish: User-friendly shell

Libraries​

Shared functions:

  • libc: Standard C library
  • Others: Specialized libraries

Services​

Background programs:

  • systemd: Service manager
  • cron: Task scheduler
  • sshd: SSH server

Kernel Space​

Linux Kernel​

The core of the system:

  • Process Management: Creation, scheduling, termination
  • Memory Management: Allocation, swap, protection
  • File System: VFS, file management
  • Network Management: TCP/IP stack, interfaces
  • Device Management: Hardware drivers

System Calls (Syscalls)​

Interface between User Space and Kernel Space:

  • open(), read(), write(): Files
  • fork(), exec(): Processes
  • socket(), bind(): Network
  • mmap(): Memory

Communication Between Layers​

Typical Flow​

Hardware Components​

CPU​

  • Instruction execution
  • Process management
  • Scheduling

RAM Memory​

  • Temporary storage
  • Data and code in execution
  • System cache

Hard Disk​

  • Persistent storage
  • File system
  • Swap (RAM extension)

Network​

  • Network interfaces
  • Communication with other systems
  • Network protocols

User/Kernel Space Separation​

Why this Separation?​

Security:

  • Applications cannot directly access hardware
  • Protection against errors
  • Process isolation

Stability:

  • Error in an application does not affect the kernel
  • System remains stable even if an app crashes

Performance:

  • Kernel optimized for hardware
  • Applications can be less optimized

Summary​

In this chapter, you learned:

Architecture: User Space + Kernel Space + Hardware
User Space: Applications, Shell, Libraries, Services
Kernel Space: Linux Kernel, System Calls, Resource Management
Communication: Via system calls (syscalls)
Separation: Security, stability, performance
Hardware: CPU, RAM, Disk, Network

Next Steps​

Chapter 1.5: Fundamental Concepts
Chapter 1.6: Installation and First Use

Chapter created on: December 2024