Java command not working in docker container

Question

I am trying to run java with docker image in gitlab.

Here is my docker file.

  FROM java:latest
  FROM perl
  COPY . /
  ENTRYPOINT ["/usr/bin/perl", "/myapp_entrypoint.pl"]

I was able to build docker image successfully and run perl commands but java commands are not working.

My application is a linux application and I am running 'java -version'. I am not getting any output completely blank output for version command.

What would be the issue? Do I need to add anything related linux as I am running 'java -version' as linux command?

Makoto · Accepted Answer · 2018-07-26 15:00:09Z

1

You don't specify what OS you're running in your container, but the main issue is that you're blowing away your Java layer with another FROM directive.

From the documentation, emphasis mine:

Each FROM instruction clears any state created by previous instructions.

So I'd espouse a solution in which I install Perl (if I really needed to) after having my base Java image.

However, if you use the base OpenJDK images, Perl comes preinstalled, so that will simplify your Dockerfile significantly.

FROM openjdk:latest
COPY . /
ENTRYPOINT ["/usr/bin/perl", "/myapp_entrypoint.pl"]

answered Jul 26, 2018 at 15:00

Makoto

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3 Comments

Techie Over a year ago

Thank you so much. It is working now. One doubt , If FROM removing previous state then what if I have more than 1 dependancies and I want to utilize all of them? Like in my problem I need both perl and java .So, what if openjdk image is not having in-built perl?

Makoto Over a year ago

@Rekha: Install it like you would on any modern OS. Specify the command line argument (yum, apt, etc) and perform an installation of what you need in your Dockerfile.

Techie Over a year ago

An example would be more helpful to understand this. Could you provide an example ?

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