Build a Docker Image

https://github.com/docker/labs/blob/master/developer-tools/java/chapters/ch03-build-image.adoc

1. 這篇文章介紹瞭如何構架docker鏡像；
2. 通過dockerfile創建docker鏡像，dockerfile中有相關指令；
3. 常用命令：

   作用	例子
   ROM	Dockerfile中第一條命令
   OPY	拷貝文件到容器指定目錄
   NV	設置環境變量
   UN	執行命令
   MD	執行容器命令
   XPOSE	指定監聽端口

4. 創建一個目錄hellodocker，創建一個Dockerfile

   FROM ubuntu:latest
   
   CMD ["/bin/echo", "hello world"]
   

5. 創建鏡像

   docker image build . -t helloworld
   

   輸出

   Sending build context to Docker daemon 2.048kB
   Step 1/2 : FROM ubuntu:latest
   latest: Pulling from library/ubuntu
   9fb6c798fa41: Pull complete
   3b61febd4aef: Pull complete
   9d99b9777eb0: Pull complete
   d010c8cf75d7: Pull complete
   7fac07fb303e: Pull complete
   Digest: sha256:31371c117d65387be2640b8254464102c36c4e23d2abe1f6f4667e47716483f1
   Status: Downloaded newer image for ubuntu:latest
   —> 2d696327ab2e
   Step 2/2 : CMD /bin/echo hello world
   —> Running in 9356a508590c
   —> e61f88f3a0f7
   Removing intermediate container 9356a508590c
   Successfully built e61f88f3a0f7
   Successfully tagged helloworld:latest

6. 通過查看鏡像，可以看到 docker image list

   REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
   helloworld          latest              e61f88f3a0f7        3 minutes ago       122MB
   ubuntu              latest              2d696327ab2e        4 days ago          122MB
   

7. 通過命令行創建容器，可以看到輸出了hello world

   docker container run helloworld
   

   輸出：

   hello world