# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx v2 3e3413f5d526 3 hours ago 109MB
ubuntu 14.04 2ff3b426bbaa 3 days ago 188MB
nginx latest 3448f27c273f 8 days ago 109MB
# cat Dockerfile
FROM nginx
RUN echo '<h1>Hello, Docker!1111111111</h1>' > /usr/share/nginx/html/index.html
# docker build -t nginx:v3 .
Sending build context to Docker daemon 2.048kB
Step 1/2 : FROM nginx
---> 3448f27c273f
Step 2/2 : RUN echo '<h1>Hello, Docker!1111111111</h1>' > /usr/share/nginx/html/index.html
---> Running in 0b2ccc2b562b
---> a3bb8892de9c
Removing intermediate container 0b2ccc2b562b
Successfully built a3bb8892de9c
Successfully tagged nginx:v3
命令解释：指定最终镜像的名称 -t nginx:v3
从命令的输出结果中，我们可以清晰的看到镜像的构建过程。在 Step 2 中，如同我们之前所说的那样，RUN 指令启动了一个容器 0b2ccc2b562b，执行了所要求的命令，并最后提交了这一层 a3bb8892de9c，随后删除了所用到的这个容器 0b2ccc2b562b。
# docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
nginx v3 a3bb8892de9c 8 minutes ago 109MB
nginx v2 3e3413f5d526 4 hours ago 109MB
ubuntu 14.04 2ff3b426bbaa 3 days ago 188MB
nginx latest 3448f27c273f 8 days ago 109MB
用这个镜像启动个容器看看：
# docker run --name webserver3 -d -p 82:80 nginx:v3
8e5842cb984a9e1033df9792fecdb906a60ff5a39a7d4f4077954d8fc13fc814
# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
8e5842cb984a nginx:v3 "nginx -g 'daemon ..." 2 minutes ago Up 2 minutes 0.0.0.0:82->80/tcp webserver3
50f00085b48f nginx:v2 "nginx -g 'daemon ..." 3 hours ago Exited (0) 20 minutes ago webserver2
e033ce3a2d90 nginx "nginx -g 'daemon ..." 5 hours ago Exited (0) 20 minutes ago webserver1
# curl http://localhost:82
<h1>Hello, Docker!1111111111</h1>