Dockerfile parameters Description: https: //docs.docker.com/engine/reference/builder/
Explain the meaning of Directive
FROM: FROM debian: stretch represented debian: stretch as the base image build
MAINTAINER: maintainer information
RUN: RUN can be seen with the reasons behind the fact that some shell commands, connected by && these scripts execution in a row, doing so is to reduce the number of layers of the mirror, each additional line will give mirrored RUN an additional layer, so here choose to execute all commands linked together to reduce the number of layers
ARG: will specifically explain later in the RUN command, this command can make some macro definitions, for example, I define ENV JAVA_HOME = / opt / jdk, after shell behind the RUN command $ {JAVA_HOME} will be replaced / opt / JDK
ENV: this effect can be seen that the instruction is to set some environmental variables (actually export) in the shell
FROM ... AS ...: this is Docker 17.05 and the new version out of the above instructions, in fact, to this stage of the image from the individual names: FROM ...(基础镜像) AS ...(别名)directly using an alias when referring to this stage of the mirror behind it
COPY:. (. Represents a current folder, the folder i.e. Dockerfile) the name implies, is used to copy files back and forth, COPY / root / workspace / agent shows a current folder so that files are copied to the container / root / workspace / agent folder. --From parameter may also come from the front stage by mirror copy files, such as --from = builder ratio indicates that the file is not a source of the local file system, but before builder alias container
WORKDIR: performing RUNin front of the rear shell commands will first cdinto WORKDIRthe back of the catalog
ENTRYPOINT: This parameter represents the image of the "portal", after the mirror package is complete, execute the image using the docker run command is actually executed behind this ENTRYPOINT executable file (usually a shell script file), or by [ "can execute file "," parameter 1 "and" parameter 2 "] this gives way to the execution parameters of the executable file, the" entrance "of the implementation of the working directory is the directory that behind WORKDIR
Each command Detailed
FROM
Designated as a new kind of mirror image of the base image, such as:
FROM ubuntu:14.04
MAINTAINER
The authors indicate mirror and its e-mail, such as:
MAINTAINER vector4wang "[email protected]"
RUN
In the new command execution inside mirror, such as to install some software, some basic configuration environment can be used \ to wrap, such as:
RUN echo 'hello docker!' \ > /usr/local/file.txt
Format may be used exec RUN ["executable", "param1", "param2"]command, such as:
RUN ["apt-get","install","-y","nginx"]
Note that, executablea command, followed by the parameter param
COPY
Copy files to the host in the mirror, if the destination does not exist, Docker will automatically create all the required directory structure, but it's just a simple copy and extract and decompress files do not work. Such as:
COPY application.yml /etc/springboot/hello-service/src/resources
Note: You need to copy the directory must be on file in the same directory Dockerfile next
reason:
Because the build environment will be uploaded to Docker daemon, and copying is carried out in Docker daemon. Any building situated outside environment things are not available. COPY instruction of the position of the object must be an absolute path inside the container.
--- "THE DOCKER BOOK"
ADD
Copy the host's file to the mirror, like COPY, limiting conditions and usage patterns are the same, such as:
ADD application.yml /etc/springboot/hello-service/src/resources
However ADD Compressed files (tar, gzip, bzip2, etc) do the extraction and decompression operations.
EXPOSE
Exposure image for the host port mapping done when boot image, in terms of a random parameter -P port mirrored host port mapping doing. Use (to specify s):
EXPOSE 8080 EXPOSE 8081 ...
WORKDIR
When building image, specify the working directory mirroring, after the commands are based on this working directory, if does not exist, create the directory. Such as
WORKDIR /usr/local WORKDIR webservice RUN echo 'hello docker' > text.txt ...
The final will /usr/local/webservice/generate a file in the directory text.txt
ONBUILD
When a mirror is used as the command contains ONBUILD base image of the other mirror (such as the user's needs to a mirror position ready to add to the source code, or the user needs to perform the specific image build script from the build environment), the command it will be executed.
The create a mirror image-A
FROM ubuntu ... ONBUILD ADD . /var/www ...
Then create a mirror image-B, as the image-A specifies the base image, such as
FROM image-A
...
Then, when the image-B constructed, displayed on the log follows:
Step 0 : FROM image-A # Execting 1 build triggers Step onbuild-0 : ADD . /var/www ...
USER
The specified what kind of image the user to perform, such as:
USER mongo
VOLUME
To add the volume-based containers for image creation. For example, you can file mongodb image data stored in the data file to specify a host. (Interior of the vessel is not recommended to store any data)
such as:
VOLUME /data/db /data/configdb
note:VOLUME 主机目录 容器目录
CMD
When you start a command vessel to be performed, such as:
CMD /bin/bash
Also you can use exec syntax, such as
CMD ["/bin/bash"]
When there are multiple CMD, only the last one will work.
ENTRYPOINT
Exactly the same role and usage and CMD
The difference between the CMD and ENTRYPOINT
Knock blackboard! ! ! Very important
we must pay attention!
We must pay attention!
We must pay attention!
CMD and ENTRYPOINT same as the command to execute when the container is started, the difference between the following points:
- CMD command will be overwritten docker run the command does not ENTRYPOINT
The use CMD ["/bin/bash"]or ENTRYPOINT ["/bin/bash"]after use re- docker run -ti imagestarting container, it automatically enters the interior of the container interactive terminal, as used
docker run -ti image /bin/bash.
But if the mirror command to start docker run -ti image /bin/ps, use the back of the CMD command will be executed instead covered by bin/psthe command, and ENTRYPOINT is not, but will docker behind the run command to execute the command as a parameter ENTRYPOINT .
The following examples easier to understand
Dockerfile for
... ENTRYPOINT ["/user/sbin/nginx"]
Then after by starting build container
docker run -ti image -g "daemon off"
At this point -g "daemon off"will be passed as a parameter to ENTRYPOINT, eventually turned into a command
/user/sbin/nginx -g "daemon off"
- CMD and ENTRYPOINT exist when
When there ENTRYPOINT and CMD, CMD command parameters into a ENTRYPOINT, and this parameter CMD is provided behind the cover docker run command, such as:
... ENTRYPOINT ["echo","hello","i am"] CMD ["docker"]
After the start of construction of the container after
-
use
docker run -ti imageOutput "hello i am docker"
-
use
docker run -ti image worldOutput "hello i am world"
Command more, you can go by memory classification (such as tables beginning) way
Examples
Himself wrote a simple example, a very simple
FROM ubuntu MAINTAINER vector4wang [email protected] WORKDIR /usr/local/docker ADD temp.zip ./add/ COPY temp.zip ./copy/ EXPOSE 22 RUN groupadd -r vector4wang && useradd -r -g vector4wang vector4wang USER vector4wang ENTRYPOINT ["/bin/bash"]
Here is the process of running
(Dynamic map can not be too large to upload)
ADD attention username and login after, COPY into files
postscript
These are just writing your own demo and browse other people by looking at the blog summed up, after some practical problems in the process of actual combat will encounter additional room.
Link: https: //www.jianshu.com/p/10ed530766af