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In my use case I would like to have two jar files in the containers. In typical docker image, I see an entry point, which basically starts the jar file. In my case, I will not know which program to be started, till the time the container is getting used in the K8s services. In my example, I have a jar file that applies the DDLs and the second Jar file is my application. I want the k8s to deploy my DDL application first and upon completion it will deploy my spring boot application (from a different jar but from same container ) next. There by I cannot give an entry point for my container, rather I need to run the specific jar file using command and argument from my yaml file. In all the examples I have come across, I see an entry point being used to start my java process.

The difference here from the post referred here is- i want to have the container to have two jar files and when I load the container through k8s, I want to decide which program to run from command prompt. One option I am exploring is to have a parametrized shell script, so I can pass the jar name as parameter and the shell will run java -jar . I will update here once I find something

solution update Add two jars in the docker file and have a shell script that uses parameter. Use the below sample to invoke the right jar file form the K8s yaml file

spec: containers:
- image: URL imagePullPolicy: Always name: image-name command: ["/bin/sh"] args: ["-c", "/home/md/javaCommand.sh jarName.jar"]
ports: - containerPort: 8080
name: http

vinSan
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    Have you considered using e.g. a bash script as your entrypoint and pass the jar file(s) to run as arguments to that script at run-time? – chash Oct 03 '19 at 20:34
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    Can you build two separate images, one for each jar file? Or else, specify the command to run in your pod spec? – David Maze Oct 04 '19 at 00:48
  • Possible duplicate of [Can I run multiple programs in a Docker container?](https://stackoverflow.com/questions/19948149/can-i-run-multiple-programs-in-a-docker-container) – Raedwald Oct 04 '19 at 09:25
  • The difference here from the post referred here is- i want to have the container to have two jar files and when I load the container through k8s, I want to decide which program to run from command prompt. One option I am exploring is to have a parametrized shell script, so I can pass the jar name as parameter and the shell will run java -jar . I will update here once I find something – vinSan Oct 04 '19 at 12:04

2 Answers2

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A docker image doesn't have to run a java jar when starting, it has to run something.

You can simply make this something a bash script that will make these decisions and start the jar you like

Nir Levy
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  • we placed two jar files in the docker image and we also had a shell script with parameter. Used the yaml file to call the respective JAR file by passing it as command – vinSan Oct 04 '19 at 22:27
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Try to add the per-requisites in the Init Containers while deploying it to kubernetes and in the regular container you can place your application, it will make DDLs container to be initialized first and then the following application container can be executed.

Tushar Mahajan
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