Part 1: Orientation and setup

`Docker` 概念

What is docker?

Docker is a platform for developers and sysadmins to develop, deploy, and run applications with containers. The use of Linux containers to deploy applications is called containerization.

Containerization is increasingly popular because containers are:

Flexible, Lightweight, Interchangeable, Portable, Scalable, Stackable

Images and Containers

Image：包含所有运行一个程序所需环境的可执行包。比如：其中的代码，库文件，环境变量，配置文件等等。一个 container 通过运行一个 image 启动。
containers：运行一个 image 的实例，或者说一个拥有状态和用户进程的 image。你可以使用以下的命令查看正在运行的实例：
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$ docker ps

Containers and Virtual machines

A container runs natively on Linux and shares the kernel of the host machine with other containers. It runs a discrete process, taking no more memory than any other executable, making it lightweight.
By contrast, a virtual machine (VM) runs a full-blown “guest” operating system with virtual access to host resources through a hypervisor. In general, VMs provide an environment with more resources than most applications need.

测试 `Docker` 的版本

通过以下的命令查看 docker 的版本：

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$ docker --version
Docker version 17.12.1-ce, build 7390fc6

# view even more details about your docker installation with following command:
$ docker info
Containers: 0
 Running: 0
 Paused: 0
 Stopped: 0
Images: 0
...

测试 `Docker` 的安装

以下的命令会自动运行一个测试 image，若未安装，该命令会自动下载镜像：

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$ docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
d1725b59e92d: Pull complete 
Digest: sha256:0add3ace90ecb4adbf7777e9aacf18357296e799f81cabc9fde470971e499788
Status: Downloaded newer image for hello-world:latest
...

通过之前的查看命令，可以看到 hello-world 这个 image 已经被安装到了机器上：

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$ docker image ls

List the hello-world container (spawned by the image) which exits after displaying its message. If it were still running, you would not need the --all option:

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$ docker container ls --all

命令总结

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## List Docker CLI commands
docker
docker container --help

## Display Docker version and info
docker --version
docker version
docker info

## Execute Docker image
docker run hello-world

## List Docker images
docker image ls

## List Docker containers (running, all, all in quiet mode)
docker container ls
docker container ls --all
docker container ls -aq