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Chapter 2.1 - Overview of the Architecture

Learning Objectives​

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

  • Understand the separation between User Space and Kernel Space
  • Identify the responsibilities of each system component
  • Visualize communication flows
  • Understand the concepts of process and memory

Layered Architecture​

Linux follows a well-defined layered architecture:

User Space vs Kernel Space​

User Space​

Role: Run user applications and programs

Characteristics:

  • Contains all the applications you use
  • Limited access to hardware (via system calls)
  • Isolation between processes
  • User permissions management

Components:

  • User applications (browser, editor, etc.)
  • Shell and command line
  • System libraries (libc, etc.)
  • Services and daemons

Kernel Space​

Role: Manage system resources and hardware

Characteristics:

  • Direct access to hardware
  • Process and memory management
  • File system
  • Network and devices
  • Protection and security

Components:

  • Linux Kernel
  • Hardware drivers
  • Memory management
  • Virtual File System (VFS)

Communication Flows​

1. User → Shell → Application​

2. Process → Kernel → Hardware​

3. systemd → Services → Kernel​

Kernel Architecture​

The Linux Kernel is organized into several subsystems:

Main subsystems:

  1. Process Management

    • Scheduling
    • Creation and termination
    • Inter-process communication

  2. Memory Management

    • Dynamic allocation
    • Virtual memory
    • Swap

  3. File System

    • VFS (Virtual File System)
    • Multiple FS support
    • Cache and buffers

  4. Network Management

    • TCP/IP stack
    • Network interfaces
    • Firewall

  5. Device Management

    • Drivers
    • Plug and play
    • Power management

Init Process and systemd​

The init process (PID 1) is the first process launched at startup:

Roles of systemd:

  • First process (PID 1)
  • Parent of all processes
  • Service management
  • Process monitoring
  • Runlevel management

Summary​

In this chapter, you learned:

Layered Architecture: Application → System → Hardware
User Space: User applications and programs
Kernel Space: System and hardware management
Communication: Flows via system calls (syscalls)
Kernel: Organized into specialized subsystems
systemd: First process, service management

Next Steps​

Now that you understand the overall architecture:

Chapter 2.2: Linux Kernel - The Heart of the System
Chapter 2.3: Memory Management and Swap

Chapter created on: December 2024