Dockerfile instructions and actual combat

1. Introduction to Dockerfile

Dockerfile is a file used to build a docker image and is a command script.
Build steps:

1. Write a dockerfile file
2. docker build builds into a mirror
3. docker run run the image
4. Docker push release image (DockerHub, Alibaba Cloud image warehouse)

We can check how the

official image is written. The official image is a basic package, and many functions are not available. We usually build our own image.

2. Dockerfile build process

Basic knowledge:

• Each reserved keyword (command) must be in uppercase letters
• Execution is executed sequentially from top to bottom
• # Indicates a comment
• Every instruction will create a new mirror and submit

• Dockerfile is development-oriented. If we want to publish projects and mirror images in the future, we need to write a dockerfile file, which is relatively simple.
• Docker image has gradually become the standard for enterprise delivery, and it must be mastered
• Steps: development, deployment, operation and maintenance, all indispensable
• DockerFile: build file, define a step, source code
• Dock and images: The image generated by DockerFile is the last product to be released and run
• Docker container: The container is the server provided by the image running

3. DockerFile instruction

FROM       # 基础镜像，一切从这里开始构建
MAINTAINER # 镜像的作者 邮箱+姓名
RUN        # 镜像构建的时候需要运行的命令
ADD        # 步骤：tomcat镜像，这个tomcat压缩包,添加内容
WORKDIR    # 镜像的工作目录
VOLUME     # 挂载的目录
EXPOST     # 保留端口配置
CMD        # 指定这个容器启动的时候要运行的命令，只有最后一个会生效，可被替代
ENTRYPOINT # 指定这个容器启动的时候要运行的命令，可以追加命令
ONBUILD    # 当构建一个被继承 DockerFile 这个时候就会运行 ONBUILD 的指令，触发指令。
COPY       # 类似ADD ，将我们的文件拷贝到镜像中
ENV        # 构建的时候设置环境变量

Illustration:

4. Actual test, build your own centos

The official centos is a streamlined version, lacking good commands, such as vim, ifconfig, etc. Therefore, we create a centos with vim and ifconfig.

1. Create a dockerfile file, the file name is mydockerfile-centos

FROM centos

MAINTAINER ybg<[email protected]>

ENV MYPATH /usr/local
WORKDIR $MYPATH

RUN yum -y install vim
RUN yum -y install net-tools

EXPOSE 80

CMD echo $MYPATH
CMD echo "----end----"
CMD /bin/bash 

2. Build your own centos image

command:

docker build -f mydockerfile-centos -t ybgcentos:0.1 .

Screenshot:

3. Test run

command:

docker run -it ybgcentos:0.1 /bin/bash

Screenshot: As

you can see, vim and ifconfig tests are available, and the build of your own image is successful.