Chapter 1: Docker Basics Introduction

Knowledge Points

What is Containerization Technology

Containerization is a lightweight virtualization technology that packages applications and their dependencies into a portable container, ensuring applications run consistently in any environment.

Core Features of Containerization Technology:

• Lightweight: Compared to traditional virtual machines, containers share the host operating system kernel with less resource consumption
• Portability: Build once, run anywhere, solving the “works on my machine” problem
• Isolation: Containers are isolated from each other, providing a secure runtime environment
• Fast Startup: Second-level startup, much faster than traditional virtual machines

Docker Architecture Overview

Docker uses a client-server (C/S) architecture pattern, mainly composed of the following components:

Containers vs Virtual Machines

Traditional Virtual Machine Architecture:

flowchart TB
    subgraph HW[Hardware]
    end

    subgraph HOST[Host OS]
    end

    subgraph HYP[Hypervisor]
    end

    subgraph VM1[Virtual Machine A]
        A1[Application A]
        GOS1[Guest OS]
        A1 --> GOS1
    end

    subgraph VM2[Virtual Machine B]
        A2[Application B]
        GOS2[Guest OS]
        A2 --> GOS2
    end

    GOS1 --> HYP
    GOS2 --> HYP
    HYP --> HOST
    HOST --> HW

Docker Container Architecture:

flowchart TB
    subgraph HW[Hardware]
    end

    subgraph HOST[Host OS]
    end

    subgraph DOCKER[Docker Engine]
    end

    subgraph C1[Container A]
        A1[Application A]
    end

    subgraph C2[Container B]
        A2[Application B]
    end

    A1 --> DOCKER
    A2 --> DOCKER
    DOCKER --> HOST
    HOST --> HW

Docker Installation and Configuration

Linux System Installation

# Install Docker on Ubuntu/Debian
# Update package index
sudo apt-get update

# Install necessary packages
sudo apt-get install \
    apt-transport-https \
    ca-certificates \
    curl \
    gnupg \
    lsb-release

# Add Docker official GPG key
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg

# Add Docker official repository
echo \
  "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] https://download.docker.com/linux/ubuntu \
  $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

# Install Docker Engine
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io

# Verify successful installation
sudo docker run hello-world

CentOS/RHEL System Installation

# Install necessary tools
sudo yum install -y yum-utils

# Add Docker repository
sudo yum-config-manager \
    --add-repo \
    https://download.docker.com/linux/centos/docker-ce.repo

# Install Docker Engine
sudo yum install docker-ce docker-ce-cli containerd.io

# Start Docker service
sudo systemctl start docker
sudo systemctl enable docker

# Verify installation
sudo docker run hello-world

Windows and macOS Installation

# Windows users:
# Download Docker Desktop for Windows
# URL: https://desktop.docker.com/win/main/amd64/Docker%20Desktop%20Installer.exe

# macOS users:
# Download Docker Desktop for Mac
# URL: https://desktop.docker.com/mac/main/amd64/Docker.dmg

# Verify after installation
docker --version
docker-compose --version

Configure Docker User Permissions

# Add current user to docker group (avoid using sudo every time)
sudo usermod -aG docker $USER

# Re-login or use the following command to take effect
newgrp docker

# Test if you can run without sudo
docker run hello-world

Basic Command Operations

Image-Related Commands

# View Docker version information
docker --version
docker version    # Detailed version information
docker info      # System information

# Search for images
docker search nginx
docker search --filter stars=100 nginx  # Filter images with more than 100 stars

# Pull images
docker pull nginx                    # Pull latest nginx
docker pull nginx:1.20             # Pull specific version
docker pull ubuntu:20.04           # Pull Ubuntu 20.04

# View local images
docker images                       # List all images
docker images nginx                # List nginx-related images
docker images --format "table {{.Repository}}\t{{.Tag}}\t{{.Size}}"  # Formatted output

# Delete images
docker rmi nginx:latest             # Delete specific image
docker rmi $(docker images -q)     # Delete all images
docker image prune                  # Clean up unused images

Container-Related Commands

# Run containers
docker run hello-world                      # Run and exit
docker run -it ubuntu:20.04 /bin/bash     # Run Ubuntu interactively
docker run -d nginx                        # Run nginx in background
docker run -d -p 8080:80 nginx            # Run nginx with port mapping
docker run -d --name my-nginx nginx       # Specify container name

# View containers
docker ps                          # View running containers
docker ps -a                       # View all containers (including stopped)
docker ps --format "table {{.Names}}\t{{.Status}}\t{{.Ports}}"  # Formatted output

# Container operations
docker start my-nginx              # Start container
docker stop my-nginx               # Stop container
docker restart my-nginx            # Restart container
docker pause my-nginx              # Pause container
docker unpause my-nginx            # Unpause container

# Enter containers
docker exec -it my-nginx /bin/bash        # Enter running container
docker attach my-nginx                     # Attach to container (not recommended)

# View container logs
docker logs my-nginx               # View container logs
docker logs -f my-nginx            # Follow logs in real-time
docker logs --tail 100 my-nginx   # View last 100 lines of logs

# Delete containers
docker rm my-nginx                 # Delete stopped container
docker rm -f my-nginx              # Force delete running container
docker rm $(docker ps -aq)        # Delete all containers
docker container prune             # Clean up stopped containers

Practical Command Combinations

# One-click Docker environment cleanup
docker system prune -a             # Clean up all unused images, containers, networks
docker system df                   # View Docker disk usage

# Batch operations
docker stop $(docker ps -q)       # Stop all running containers
docker rm $(docker ps -aq)        # Delete all containers
docker rmi $(docker images -q)    # Delete all images

# Container resource monitoring
docker stats                      # Real-time view of container resource usage
docker stats my-nginx             # View specific container resource usage

# Container detailed information
docker inspect my-nginx           # View detailed container configuration
docker port my-nginx              # View container port mapping
docker top my-nginx               # View container process information

Practical Exercises

Hello World Example

# Run first Docker container
docker run hello-world

# Output explanation:
# 1. Docker client contacts Docker daemon
# 2. Daemon pulls hello-world image from Docker Hub
# 3. Creates a new container and runs the program in the image
# 4. Program outputs message and container stops

Web Server Example

# Run Nginx web server
docker run -d --name web-server -p 8080:80 nginx

# Verify service is running
curl http://localhost:8080
# Or visit http://localhost:8080 in browser

# View container status
docker ps

# View container logs
docker logs web-server

# Enter container
docker exec -it web-server /bin/bash

# Execute commands inside container
ls /usr/share/nginx/html/    # View web files
cat /etc/nginx/nginx.conf    # View nginx configuration

# Exit container
exit

# Stop and delete container
docker stop web-server
docker rm web-server

Data Persistence Example

# Create data volume and run container
docker run -d --name nginx-with-volume \
    -p 8080:80 \
    -v /tmp/nginx-data:/usr/share/nginx/html \
    nginx

# Create custom webpage on host
echo "<h1>Hello from Docker!</h1>" > /tmp/nginx-data/index.html

# Access webpage to see effect
curl http://localhost:8080

# Stop container but data remains on host
docker stop nginx-with-volume
ls /tmp/nginx-data/  # Files still exist

Common Issue Resolution

Permission Issues

# Issue: Got permission denied while trying to connect to the Docker daemon socket
# Solution: Add user to docker group
sudo usermod -aG docker $USER
newgrp docker

# Or temporarily use sudo
sudo docker run hello-world

Network Connection Issues

# Issue: Unable to pull images or connection timeout
# Solution: Configure domestic mirror sources

# Create or edit daemon configuration file
sudo mkdir -p /etc/docker
sudo tee /etc/docker/daemon.json <<-'EOF'
{
    "registry-mirrors": [
        "https://registry.docker-cn.com",
        "https://docker.mirrors.ustc.edu.cn",
        "https://hub-mirror.c.163.com"
    ]
}
EOF

# Restart Docker service
sudo systemctl daemon-reload
sudo systemctl restart docker

# Verify configuration
docker info | grep "Registry Mirrors" -A 3

Storage Space Issues

# Issue: Insufficient disk space
# Solution: Clean up Docker resources

# View disk usage
docker system df

# Clean up unused resources
docker system prune -a    # Clean up all unused images, containers, networks, build cache

# Clean up separately
docker container prune    # Clean up stopped containers
docker image prune        # Clean up unused images
docker network prune      # Clean up unused networks
docker volume prune       # Clean up unused volumes

Summary

Through this chapter, you should have mastered:

• Containerization Concepts: Understood the advantages and application scenarios of containerization technology
• Docker Architecture: Learned Docker’s core components and working principles
• Environment Setup: Completed Docker installation and basic configuration
• Basic Operations: Mastered basic management commands for images and containers
• Practical Experience: Deepened understanding of Docker through practical cases

In the next chapter, we will dive into Docker image management, including image layered structure, build process, and repository management.