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This article mainly introduces "how to build a Docker image". In daily operation, I believe many people have doubts about how to build a Docker image. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the questions of "how to build a Docker image"! Next, please follow the editor to study!

8. Advanced

In this section, I show you how to build a Docker image myself. We will build a runtime environment that supports scala and open up SSH services to the public.

8.1. Two methods of constructing Image

There are two ways to build an image:

Run and run a basic container (such as centos, docker run-it centos / bin/bash), then install the required environment, and then use commit to save the container as a new image

Build using Dockerfile, which is also recommended

In this section, we will only introduce the second method.

8.2. Dockerfile introduction

Dokcerfile is a metafile used to build a Docker image. For its description and syntax, please see: http://docs.docker.com/engine/reference/builder/

8.3. Construction planning

According to the requirements, we can find that there are three main environments we install: SSH service, Java environment (Scala depends on it), and Scala environment. Like software development, we can also build in modules, that is, build three images:

Contains only the basic image of the SSH service

Image with SSH and Java environment

Mirror with SSH, Java, and Scala environment

8.4. SSH image FROM centos:centos7 MAINTAINER gudaoxuri #-Use 163mirrors- RUN yum install-y wget & &\ mv / etc/yum.repos.d/CentOS-Base.repo / etc/yum.repos.d/CentOS-Base.repo.backup & &\ wget-P / etc/yum.repos.d/ http://mirrors.163.com/.help/CentOS7-Base- 163.repo & &\ yum clean all & &\ yum makecache #-Install Common Tools-RUN yum install-y sed curl tar gcc gcc-c++ make git passwd sudo#-Modify Time Zone-ENV TZ "Asia/Shanghai" ENV TERM xtermRUN yum install-y ntpdate & &\ cp / usr/share/zoneinfo/Asia/Shanghai / etc/localtime#-Support Chinese-#RUN yum groupinstall-y "Fonts" & &\ # echo "LANG=\" zh_CN.UTF-8\ "> > / etc/sysconfig/i18n#-Install SSH- -RUN yum install-y openssh-server openssh-clients & &\ sed-I 's/UsePAM yes/UsePAM no/g' / etc/ssh/sshd_config & &\ echo' root:123456' | chpasswd & &\ ssh-keygen-t dsa-f / etc/ssh/ssh_host_dsa_key & &\ ssh-keygen-t rsa-f / etc/ssh/ssh_host_rsa_key & & \ mkdir / var/run/sshd#-Setting Common Path-RUN chmod 777-R / opt/ & &\ mkdir / opt/env/ & &\ mkdir / opt/workspaces/EXPOSE 22 CMD ["/ usr/sbin/sshd" "- D"] FROM indicates which image this image is based on. MAINTAINER developer's information # comment RUN Common commands The command used to execute Linux, mostly used to install component ENV common commands, used to set the environment variable EXPOSE indicates the default exposed port (docker run-P) CMD to execute the service, multiple CMD only executes the last one

RUN parameter knowledge, Docker image is hierarchical, an image may be composed of multiple layers, a RUN actually produces a layer, there may be errors in the process of compiling Dockerfile, we will find that the previously successfully compiled layers will not be compiled again. Compile SSH image root@ubuntu:/opt/test/dockerfile/ssh# lsDockerfileroot@ubuntu:/opt/test/dockerfile/ssh# docker build-t gudaoxuri/ssh .Sending build context to Docker daemon 3.072 kBSending build context to Docker daemon Step 0: FROM centos:centos7Pulling repository centosce20c473cd8a: Download complete ce20c473cd8a: Pulling image (centos7) from centos 168a69b62202: Download complete 812e9d9d677f: Download complete 4234bfdd88f8: Download complete Status: Downloaded newer image for centos:centos7-> ce20c473cd8aStep 1: MAINTAINER gudaoxuri-- > Running in 889ea744c458-- > 5b1151e6cb0bRemoving intermediate container 889ea744c458 Step 10: CMD / usr/sbin/sshd-D-> Running in ce563073b686-> b61a4adad85fRemoving intermediate container ce563073b686Successfully built b61a4adad85froot@ubuntu:/opt/test/dockerfile/ssh# docker imagesREPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZEgudaoxuri/ssh latest b61a4adad85f 10 minutes ago 966 MB...8.6. Java image FROM gudaoxuri/ssh:latest MAINTAINER gudaoxuri#-Install Java-RUN wget-P / opt/env/-- no-check-certificate-- no-cookies-- header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u60-b27/jdk-8u60-linux-x64.tar.gz & &\ tar -xzf / opt/env/jdk-8u60-linux-x64.tar.gz-C / opt/env/ & &\ rm / opt/env/jdk-8u60-linux-x64.tar.gz & &\ mv / opt/env/jdk1.8.0_60 / opt/env/java &\ echo "export JAVA_HOME=/opt/env/java" > / etc/profileENV JAVA_HOME/ opt/env/javaRUN echo 'PATH=$PATH:$JAVA_HOME/bin' > > / etc/profileENV PATH $PATH:$JAVA_HOME/bingudaoxuri/ssh:latest is the mirror 8.7 that we compiled earlier. Scala image FROM gudaoxuri/java:latestMAINTAINER gudaoxuri#-Install Scala-RUN wget-P / opt/env/ http://downloads.typesafe.com/scala/2.10.6/scala-2.10.6.tgz & &\ tar-xzf / opt/env/scala-2.10.6.tgz-C / opt/env/ & &\ rm / opt / env/scala-2.10.6.tgz & &\ mv / opt/env/scala-2.10.6 / opt/env/scala & &\ echo "export SCALA_HOME=/opt/env/scala" > > / etc/profileENV SCALA_HOME/ opt/env/scalaRUN sed / ^ PATH=/d / etc/profile > > / etc/profile & &\ echo 'PATH=$PATH:$JAVA_HOME/bin:$SCALA_HOME/bin' > > / etc/profileENV PATH $PATH:$JAVA_HOME/bin:$SCALA_HOME/bin8.8. Compile the Java/Scala image

The process is the same as above.

8.9. Publish an image

After we have a new image, we want to publish this image to hub.docker.com to share. There are two ways:

Log in to docker login before using docker push to publish

Publish using github

Due to the poor domestic network environment, the failure probability of the first method is very high, because it uploads the generated image (ranging from a few hundred MB to a few gigabytes), so the second method is recommended.

Please register for hub.docker.com and github.com account 8.9.1. Publish an image using github

Do not use IE operation, the author has a lot of trouble when using IE11 to operate on hub.docker.com.

Establish a github connection on hub.docker.com

Set permissions in github

To build an open source project in github, be careful to include the Dockerfile file

Set permissions for this project in github

Set up an automatic build project on hub.docker.com

Select a project on github on hub.docker.com

Set project properties on hub.docker.com

It won't be long before it's built.

At this point, the study on "how to build a Docker image" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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