How to pass System property to docker containers?

Question

So I know you can pass Environment variables to a docker container using -e like:

docker run -it -e "var=var1" myDockerImage

But I need to pass a System Property to a docker container, because this is how I run my JAR:

java -Denvironment=dev -jar myjar.jar 

So how can I pass a -D System property in Docker? Like:

docker run -it {INSERT Denvironment here} myDockerImage

Answer 1

One more way to do it, if running under Tomcat, is setting your system variables in your Dockerfile using ENV JAVA_OPTS like this:

ENV JAVA_OPTS="-Djavax.net.ssl.trustStore=C:/tomcatDev.jks -D_WS_URL=http://some/url/"

Hope it helps!

Answer 2

One can also use the following start.sh ENTRYPOINT for the Docker container, make sure to use the array syntax, e.g.:

Dockerfile:

...
ENTRYPOINT ["/start.sh"]

The actual start.sh script:

#!/bin/bash
export JAVA_HOME="/usr/lib/jvm/java-8-openjdk-amd64"
exec $JAVA_HOME/bin/java -jar myjar.jar $@

Then you can just pass the Java system properties directly to your application as docker run container arguments:

docker run myDockerImage "-Dvar=var1"

Answer 3

Have a start.sh file, e.g.:

#!/usr/bin/env sh
exec java -Djava.security.egd=file:/dev/./urandom $* -jar /app.jar

In your Dockerfile:

...
COPY start.sh /start.sh
RUN chmod a+rx /start.sh
ENTRYPOINT ["/start.sh"]