Shulou(Shulou.com)06/03 Report--

We can learn from the previous article that the customization of the image is actually customizing the configuration, files and other information added by each layer, but after all, the command is only a command, and each customization has to repeat this command, and it is not intuitive enough. If we can write the commands for modifying, installing, building and operating each layer into a script, use this script to build and customize the image Then all these problems can be solved? Yes, this script is what we call Dockerfile.

Introduction

Dockerfile is a text file that contains Instruction, each of which builds a layer, so the content of each instruction is to describe how the layer should be built.

Here we take the custom tomcat image as an example, this time we use Dockerfile to customize it. In a blank directory, create a text file and name it Dockerfile:

[root@192 mydocker] # cat DockerfileFROM jdk:latestADD apache-tomcat-9.0.27.tar.gz / data/softRUN rm-rf apache-tomcat-9.0.27.tar.gzWORKDIR / data/soft/ENTRYPOINT / data/soft/apache-tomcat-9.0.27/bin/startup.sh & & tail-f / dev/null [root@192 mydocker] # docker build-t tomcat:test .Sending build context to Docker daemon 500.2MBStep 1 FROM jdk:latest-> d8252cab0866Step 2max 5 : ADD apache-tomcat-9.0.27.tar.gz / data/soft-- > d0f4873733b8Step 3Running in 90dfd42c6134Removing intermediate container 90dfd42c6134 5: RUN rm-rf apache-tomcat-9.0.27.tar.gz-- > Running in 7d54b3ccd7caRemoving intermediate container 7d54b3ccd7ca-- > 1f07735cd7daStep 4 WORKDIR 5: WORKDIR / data/soft/-- > Running in 90dfd42c6134Removing intermediate container 90dfd42c6134-- > 5704cc83ebb3Step 5 data/soft/apache-tomcat-9.0.27/bin/startup.sh 5: ENTRYPOINT / data/soft/apache-tomcat-9.0.27/bin/startup.sh & & tail-f / dev/null -> Running in 5dd6eef5777eRemoving intermediate container 5dd6eef5777e-> d97a77aa1533Successfully built d97a77aa1533Successfully tagged tomcat:test [root@192 mydocker] # docker run-- name webserver-d-p 8080 name webserver-d-p 8080 tomcat:test / bin/bashe13e5b4d7807b5dbeec0eb55192602ed60cb289b95d82a455cdb340581aba150 [root@192 mydocker] # netstat-lntpActive Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program nametcp 00 0.0.0.0 22 0.0.0. 0LISTEN 1093/sshd * LISTEN 1093/sshdtcp6 0 0: 8080: * LISTEN 48659/docker-proxytcp6 0 0: 22: * LISTEN 1093/sshd is accessed through the browser

Common instruction

Pay attention to the problem

The use of COPY ADD will design the problem of permissions. How to solve the problems of permissions?

You can use COPY-chown= or ADD-chown= to solve the problem

In the process of use, such as ADD uses the .tar.gz automatic decompression function, after the execution of build, the permissions in the package will not change. Then the COPY direct use right is directly changed to root.

The use of USER and which uses are affected

Affect the execution identity of the subsequent RUN CMD ENTRYPOINT commands, note that the COPY commands are not obeyed

The use of WORKDIR

Switch directories

An example

RUN cd / test

RUN echo "test" > test.txt

Is there / test/test.txt in the last image? A: NO

Explanation: there is a concept of layers in docker. Each command generates a layer, and each layer is a separate space. So on the second RUN, the working directory does not change to / test. Finally, a picture is used to explain the meaning of common instructions ^-^.

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