Docker in Action 2e d - Ch1 Welcome to Docker

3. Why is Docker important?
4. Where and when to use Docker
5. Docker in the larger ecosystem
6. Getting help with the Docker command line

Resources

• book website => 線上全文、電子版購買、討論
• Docker hub repos
• GitHub repos

Running for the first time

Running for the first time

Run again

Run again

Naming

• jail => 1979 Unix-like OS，限制資源取用的執行環境。
• container => 2005 Solaris 10，以白名單模式限制程式取用資源。
• 有許多書中未提及的實作，如 1982 Unix-like OS 的 chroot，可參考 wikipedia。

Running software in containers for isolation

直接執行程式

透過 Docker 執行

Docker 使用 Linux 中 namespaces 跟 cgroups 來孤立每個 container。

Docker 使用下列系統特性來建立 containers:

• PID namespace - Process identifiers and capabilities
• UTS namespace - Host and domain name
• MNT namespace - Filesystem access and structure
• IPC namespace - Process communication over shared memory
• NET namespace - Network access and structure

Docker 使用下列系統特性來建立 containers:

• USR namespace - User names and identifiers
• chroot syscall - Controls the location of the filesystem root
• cgroups - Resource protection
• CAP drop - Operating system feature restrictions
• Security modules - Mandatory access controls

Images become containers when they run on Docker Engine.

https://www.docker.com/resources/what-container

不用 Docker

• 要在某個機器上，使用某套程式，其前置作業很痛苦 => 支援的 OS、安裝順序、調整設定、依賴軟體、依賴軟體的依賴軟體，還有他們的版本問題。
• 程式沒有隔離 => 版本不同、依賴不同、髒資料問題。

使用 Docker

使用 Docker

• 優雅的使用，不用考慮管理問題。
• 各程式獨立運作，包含它們的依賴。

• 行成生態系，改變了系統管理、開發、部署的做法；省時間、省錢、省精力。
• 促進社群（包含 Amazon、Microsoft、Google）使用其與 Container 技術，進而讓它們更多選擇開源專案而非自建輪子。

• 其特性使其成為跨平台系統的 App Store，其於原本的 Desktop 系統體系上所缺乏的。
• 讓大家更重視在 OS 上的孤立執行環境。

Docker Architecture

Docker uses a client-server architecture

Docker Architecture

• Docker Server
  • Daemon(dockerd)
    • listens for Docker API requests
    • manages Docker objects such as images, containers, networks, and volumes
    • can also communicate with other daemons to manage Docker services.

Docker Architecture

• Docker Object
  • Images
    • a read-only template with instructions for creating a Docker container
    • an image is based on another image, with some additional customization
    • To build your own image, you create a Dockerfile with a simple syntax for defining the steps needed to create the image and run it

Docker Architecture

• Docker Object
  • Containers
    • a runnable instance of an image
    • is relatively well isolated from other containers and its host machine

Docker Architecture

• Client
  • users interact with Docker
  • docker command uses the Docker API
  • use commands such as docker run, the client sends these commands to dockerd

Docker Architecture

• Registry
  • A Docker registry stores Docker images
  • Docker Hub is a public registry that anyone can use
  • You can even run your own private registry, ex: Harbor(企業等級)

• 許 Docker Plugin 或以 Docker 為核心的解決方案出現。
• Docker 也貢獻了部分如 runc、libcontainerd、notary。

E.g. Kubernetes

• Extensible platform for orchestrating services as containers in clustered environments.

• Depends on container engines such as Docker.

• Today building, customizing, or extending Kubernetes clusters is a full-time job.

• This book focuses on and teaches solutions to higher-level problems using Docker alone.

問題1: xxxxxxxx

問題 2: xxxxxx