Docker Basics

Docker Basics — 概念与基础

Docker 生态的第一入口。从零理解 Docker 概念、架构和基础操作。

When to Use

Core Concepts

Container vs VM

Docker Architecture

┌─────────────────────────────┐
│         Docker CLI           │  ← docker build/run/push...
├─────────────────────────────┤
│       Docker Daemon          │  ← dockerd: manages images, containers, networks, volumes
├─────────────────────────────┤
│       containerd             │  ← container runtime supervisor
├─────────────────────────────┤
│        runc                  │  ← OCI runtime (actually runs containers)
└─────────────────────────────┘
         │
    ┌────┴────┐
    ▼         ▼
 Registry   Host OS
 (Docker    (Linux kernel:
  Hub)       namespaces, cgroups)

Quick Start

# Verify installation
docker --version
docker run hello-world

# Pull and run your first container
docker pull nginx:alpine
docker run -d -p 8080:80 --name my-nginx nginx:alpine

# Check it's running
curl localhost:8080
docker ps
docker stop my-nginx

Docker Object Model

docker run → Container (running instance of an image)
docker build → Image (built from Dockerfile)
docker pull → Image (downloaded from Registry)
docker push → Image (uploaded to Registry)
docker volume → Volume (persistent data)
docker network → Network (container communication)

Installation Path

Key CLI Groups

docker container   → create, run, start, stop, rm, ls, inspect, logs, exec
docker image       → build, pull, push, tag, ls, rm, prune, inspect
docker volume      → create, ls, rm, prune, inspect
docker network     → create, ls, rm, inspect, connect, disconnect
docker system      → df, prune, info, events

Workflow — 推荐学习路径

Step 1: 理解概念: 阅读 Core Concepts（Image/Container/Registry/Engine） Step 2: 安装验证: docker run hello-world 确认安装成功 Step 3: 第一个容器: docker run -d -p 8080:80 nginx:alpine 体验 Step 4: 进阶学习: 掌握 docker build（写 Dockerfile）→ docker run（管理容器） Step 5: 进入生态: 按需探索 docker-dockerfile/docker-build/docker-compose

Gotchas — Common Pitfalls

• Image vs Container confusion: docker run creates a NEW container each time. → Recovery: Use docker start <name> to restart an existing container; docker ps -a to see stopped containers.
• Root permission: Linux requires sudo unless user is added to docker group (security risk: docker group = root access). → Recovery: sudo usermod -aG docker $USER && newgrp docker or use rootless Docker.
• Disk bloat: Old images/volumes/cache accumulate fast. → Recovery: docker system prune -a monthly; check with docker system df first.
• Port conflict: -p 8080:80 means host:8080 → container:80. If host port is taken, change host side. → Recovery: lsof -i :8080 to find process occupying the port, then use a different port.
• Data loss: Without volumes, container data is ephemeral. → Recovery: Always use -v volume_name:/data for stateful data; never rely on container filesystem.

Boundary — 能力边界（适用与不适用场景）

When NOT to Use This Skill

Security & Stability

• All examples are educational. Use official images and verified publishers in production.
• Docker group membership on Linux is equivalent to root access.
• No executable scripts bundled. This skill teaches concepts and basic operations.

📚 官方文档参考

🧭 Docker Skills Journey

📍 You are here: `docker-basics` — Step 1: Docker 概念与基础

basics → build → run → networking/storage → compose → security/cicd → production/troubleshooting → ai-ml

→ Next: docker-build — Write Dockerfiles and build optimized images

FAQ

Q1: 如何快速上手此技能？ A: 参考上方的快速开始章节，按步骤操作即可。

Q2: 遇到版本不兼容问题怎么办？ A: 检查依赖版本，使用 lock 文件锁定，参考常见陷阱章节。

Q3: 如何在生产环境使用？ A: 参考最佳实践章节，确保配置正确，做好监控和日志。

Q4: 性能如何优化？ A: 参考性能优化相关文档，使用缓存、索引等手段。

Q5: 如何贡献或反馈问题？ A: 在 GitHub 仓库提交 Issue 或 Pull Request。

Q6: 是否支持中文？ A: 支持中文文档和中文注释，详见国内适配章节。

Your first Docker container

# 1. Verify Docker is installed
docker --version

# 2. Run hello-world (one-off container)
docker run hello-world

# 3. Run an interactive Ubuntu container
docker run -it ubuntu:22.04 bash
# Inside: whoami / cat /etc/os-release / exit

# 4. Run a background web server
docker run -d --name my-nginx -p 8080:80 nginx:alpine
curl localhost:8080
docker stop my-nginx
docker rm my-nginx

Container lifecycle demo

# Create (doesn't start)
docker create --name demo nginx:alpine

# Start
docker start demo

# Check status
docker ps
docker ps -a

# Stop
docker stop demo

# Start again (no data loss with volumes)
docker start demo

# Remove
docker stop demo && docker rm demo

# One-liner: create, start, auto-remove on stop
docker run --rm -d --name demo nginx:alpine

Docker Architecture

Docker Client (CLI)
    ↓ REST API
Docker Daemon (dockerd)
    ├── Image Management (build/pull/push)
    ├── Container Runtime (via containerd)
    ├── Network Management (bridge/overlay/host)
    └── Volume Management (local/NFS/cloud)

containerd (container supervisor)
    ↓
runc (OCI runtime — creates containers)
    ↓
Linux Kernel (namespaces + cgroups)

Key Linux features Docker uses

Container vs VM

Virtual Machine:                   Container:
┌──────────┐ ┌──────────┐        ┌───┐ ┌───┐ ┌───┐
│  App A   │ │  App B   │        │ A │ │ B │ │ C │
├──────────┤ ├──────────┤        └─┬─┘ └─┬─┘ └─┬─┘
│ Bins/Libs│ │ Bins/Libs│        ┌─┴──────┴──────┴─┐
├──────────┤ ├──────────┤        │   Docker Engine  │
│Guest OS  │ │Guest OS  │        ├─────────────────┤
├──────────┤ ├──────────┤        │     Host OS      │
│ Hypervisor (Type 2)   │        ├─────────────────┤
├───────────────────────┤        │   Infrastructure │
│       Host OS         │        └─────────────────┘
├───────────────────────┤
│    Infrastructure     │
└───────────────────────┘

Size: GBs per VM         Size: MBs per container
Start: ~1 min            Start: ~1 sec
Density: 5-10/host       Density: 50-100/host
Isolation: Strong (HW)   Isolation: Process-level (kernel shared)

Docker 安装指南

macOS

Docker Desktop

brew install --cask docker
# 启动 Docker Desktop.app，根据向导完成

OrbStack

brew install orbstack
# 启动 OrbStack.app

Colima

brew install colima docker docker-compose
colima start --cpu 4 --memory 8 --disk 60
docker ps   # 验证

Linux

# Ubuntu/Debian
curl -fsSL https://get.docker.com | sudo sh
sudo usermod -aG docker $USER
newgrp docker

# CentOS/RHEL/Fedora
sudo dnf install docker-ce docker-ce-cli containerd.io
sudo systemctl enable --now docker

Windows

• WSL 2 + Docker Desktop（推荐）
• winget install Docker.DockerDesktop

验证安装

docker --version
docker compose version
docker run --rm hello-world

卸载

# macOS（Docker Desktop）
brew uninstall --cask docker

# Linux
sudo apt purge docker-ce docker-ce-cli containerd.io
sudo rm -rf /var/lib/docker /var/lib/containerd