This cookbook aims at providing for java developers a quick, easy way to build their own docker image that can be used to create the containers needed for automatic builds.
- Ubuntu 14.04, 16.04 16.10, CenOS 6.8, CenOS 7, Window 10, Window 7
- Docker, Docker-Compose (https://www.docker.com/)
Starting with Dockerfile
Docker builds images by reading instructions from a Dockerfile.
A Dockerfile is a simple text file that contains instructions that can be executed on the command line.
Using docker build, you can start a build that executes all of the command-line instructions contained in the Dockerfile.
See more https://docs.docker.com/engine/getstarted/step_four/#step-1-write-a-dockerfile
Common Dockerfile instructions start with RUN, ENV, FROM, MAINTAINER, ADD, and CMD, among others.
- FROM – Specifies the base image that the Dockerfile will use to build a new image. For this post, we are using phusion/baseimage as our base image because it is a minimal Ubuntu-based image modified for Docker friendliness.
- MAINTAINER – Specifies the Dockerfile Author Name and his/her email.
- RUN – Runs any UNIX command to build the image.
- ENV – Sets the environment variables. For this post, JAVA_HOME is the variable that is set.
- CMD – Provides the facility to run commands at the start of container. This can be overridden upon executing the docker run command.
- ADD – This instruction copies the new files, directories into the Docker container file system at specified destination.
- EXPOSE – This instruction exposes specified port to the host machine.
Build your own Dockerfile for Java Application
See my Dockerfile for an example
# download java:8 prebuild FROM pdoviet/oracle-java:8 # add your mantainer MAINTAINER Author Name <email@example.com> #create apps directory RUN mkdir apps # copy your application to docker images ADD java/java-app /apps/java-app WORKDIR /apps/java-app # run your application # OPTION 1 : Run java application with dependencies CMD ["java","-cp","Main.jar", "Main"] # OPTION 2 : Run direct your application ( not recommended) #CMD ["java","Main"]
You can download my source code from GitHub
git clone https://github.com/phuongdo/docker-tutorial.git cd docker-tutorial
Build your docker image
docker build -f java/your-docker/Dockerfile -t <yourname>/<your-image-name>:<version> . #Example docker build -f java/your-docker/Dockerfile -t pdoviet/your-docker-image:1 .
***NOTE: Do not forget the .(dot) at the end of command; it specifies the context of the build. The .(dot) at the end of the command specifies the current directory. The files and directories of current directory will be sent to Docker daemon as a build artifact.
This process will take a few minutes, then you can list your docker images in local machine
docker images EPOSITORY TAG IMAGE ID CREATED SIZE pdoviet/your-docker-image 1 be0aa8633f16 9 seconds ago 667 MB pdoviet/oracle-java 8 5fc2ac2d72c0 18 minutes ago 667 MB
You have built our own image successfully, now we need to test it using sample Java application.
docker run -it --rm --name your-docker-name pdoviet/your-docker-image:1 Hello World!
Some options are available:
– The -it flag starts the container in an interactive mode,
– The –rm flag cleans out the container after it shuts down,
– The –name dsp-inst names the container dsp-inst,
– The -d run on daemon mode
Login to your DockerHub with your account (please create one if you don’t have it)
docker login <docker-hub-uri>
pull to your images docker hub
docker pull <docker-hub-uri>/<your-namespace>/<your-image>:<version>
How do I list what is currently running?
How do I stop and delete a running process?
docker stop and docker rm