这里我们使用docker build和Dockerfile文件来构建镜像

基于DSL语法

[root@centos7-docker ~]# mkdir -p docker_web
[root@centos7-docker ~]# cd docker_web/
[root@centos7-docker docker_web]# touch Dockerfile

docker_web目录就是我们的构建环境，叫做上下文或构建上下文

docker会在构建时候将构建上下文和上下文中的文件，目录等上传到Docker守护进程

这样docker守护进程就能直接访问你想在镜像中存储的任何代码，文件或其他数据

[root@centos7-docker docker_web]# vim Dockerfile

# Version: 0.0.1
# this is my first Dockerfile
FROM ubuntu:14.04
MAINTAINER JamesZOU "youzhibicheng@163.com"
RUN apt-get -y update
run apt-get -y install nginx
RUN echo "Hi, I am a Docker container website" > /user/share/nginx/html/index.html
EXPOSE 80

构建

[root@centos7-docker docker_web]# docker build -t="youzhibicheng/docker_web" .
Sending build context to Docker daemon 2.048 kB
Sending build context to Docker daemon
Step 0 : FROM ubuntu:14.04
 ---> d2a0ecffe6fa
Step 1 : MAINTAINER JamesZOU "youzhibicheng@163.com"
 ---> Running in 82b429e791df
 ---> 54ec5b1ecbeb
Removing intermediate container 82b429e791df
Step 2 : RUN apt-get -y update
 ---> Running in 7fba5d13e390

......

Reading package lists...
 ---> c0865994cec0
Removing intermediate container 7fba5d13e390
Step 3 : RUN apt-get -y install nginx
 ---> Running in 6fb6b921222b

......

 ---> f0019c511de0

Removing intermediate container 6fb6b921222b
Step 4 : RUN echo "Hi, I am a Docker container website" > /user/share/nginx/html/index.html
 ---> Running in d3c9c511679b
/bin/sh: 1: cannot create /user/share/nginx/html/index.html: Directory nonexistent
INFO[0713] The command [/bin/sh -c echo "Hi, I am a Docker container website" > /user/share/nginx/html/index.html] returned a non-zero code: 2

执行流程

1. docker从基础镜像ubuntu:14.04中运行一个容器

2. 执行一条指令，对容器做出修改

3. 执行类似docker commit操作，提交心的镜像层

4. docker再基于刚提交的镜像运行一个新容器

5. 执行Dockerfile中的下一条指令，直到所有指令都执行完毕