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This article mainly introduces how to use Dockerfile in Docker, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

Description of the Dockerfile file:

Format:

INSTRUCTION arguments

Although instructions ignore case, uppercase is recommended

# is a comment

MAINTAINER command:

The MAINTAINER command is used to specify the name and contact information of the maintainer

FROM command:

FROM /:

This is to set up the basic image for subsequent commands, so it should be the first instruction of Dockerfile

For example:

FROM centos6-base

RUN command:

Execute any command in the image specified by FROM above, and then commit the result. The submitted image will be used later.

Format:

RUN (this command runs a shell in -'/ bin/sh-c')

Or:

RUN ["executable", "param1", "param2"]

The RUN command is equivalent to:

Docker run image_name command

CMD and ENTRYPOINT

Command setting executes commands when the container starts

ENTRYPOINT, which indicates the command that needs to be executed during initialization of the image. It cannot be overwritten and should be remembered.

CMD, which indicates that the default parameters for image operation can be overridden by rewriting.

ENTRYPOINT/CMD can only exist once in the file, and the last one takes effect more than one, only the last one takes effect, and the other is invalid!

You need to initialize and run multiple commands, which can be separated by & &, but keep in mind that the last command needs to be run infinitely!

ENTRYPOINT/CMD. Generally speaking, the two can be used together, such as:

ENTRYPOINT ["/ usr/sbin/sshd"]

CMD ["- D"]

* * in Docker daemon mode, whether you are using ENTRYPOINT or CMD, the last command must be the current process that needs to be running all the time to prevent the container from exiting. ***

The following invalid methods:

After ENTRYPOINT service tomcat7 start # runs for a few seconds, the container exits

After CMD service tomcat7 start # runs for a few seconds, the container exits

This works:

ENTRYPOINT service tomcat7 start & & tail-f / var/lib/tomcat7/logs/catalina.out

# or

CMD service tomcat7 start & & tail-f / var/lib/tomcat7/logs/catalina.out

This also works:

ENTRYPOINT ["/ usr/sbin/sshd"]

CMD ["- D"]

USER command

For example, if you specify the user who runs the memcached, you can use the ENTRYPOINT or CMD above to implement:

ENTRYPOINT ["memcached", "- u", "daemon"]

A better way:

ENTRYPOINT ["memcached"]

USER daemon

EXPOSE command

The EXPOSE command sets a port to be exposed in the running image.

Relevant ports are used when docker uses-- link to link two containers

EXPOSEd

ENV command:

Used to set environment changes

Create a new container using the image generated by this dockerfile, and you can see this environment variable through docker inspect CONTAINER ID

You can also set or modify environment variables during docker run

ADD command:

Copy the file from src to the dest path of container:

ADD

Is the relative path relative to the source directory being built, which can be the path of a file or directory, or a remote file url

Is the absolute path in container

VOLUME command

VOLUME ["]

Such as:

VOLUME ["/ data"]

Create a mount point for sharing directories

WORKDIR command

WORKDIR / path/to/workdir

Configure RUN, CMD, ENTRYPOINT commands to set the current work path

Can be set multiple times, if it is a relative path, then relative to the previous WORKDIR command

For example:

WORKDIR / a WORKDIR b WORKDIR c RUN pwd

Actually, pwd is executed under / a/b/c

This is the end of the introduction of Dockerfile files.

Here is a complete Dockerfile file

# DockerfileFROM centos6-baseMAINTAINER zhou_mfk RUN ssh-keygen-Q-N ""-t dsa-f / etc/ssh/ssh_host_dsa_keyRUN ssh-keygen-Q-N ""-t rsa-f / etc/ssh/ssh_host_rsa_keyRUN sed-ri 's/session required pam_loginuid.so/#session required pam_loginuid.so/g' / etc/pam.d/sshdRUN mkdir-p / root/.ssh & & chown root.root / root & & chmod 700 / root/.sshEXPOSE 22RUN echo 'root:redhat' | chpasswdRUN yum install-y yum-priorities & & rpm- ivh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm & & rpm--import / etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-6RUN yum install tar gzip gcc vim wget-yENV LANG en_US.UTF-8ENV LC_ALL en_US.UTF-8CMD / usr/sbin/sshd-D# End, thank you for reading this article carefully. I hope the article "how to use Dockerfile in Docker" shared by the editor will be helpful to everyone. At the same time, I also hope that you will support and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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