ARG values won't be available after the image is built, so a running container won’t have access to those values. You can use ENV and have something like:

ARG PATH ENV P=${PATH} CMD target/universal/rule_engine-1.0/bin/rule_engine -Dconfig.file=$P 

ARG values won't be available after the image is built, so a running container won’t have access to those values. To dynamically set an env variable, you can combine both ARG and ENV (since ENV can't be overridden):

ARG PATH ENV P=${PATH} CMD target/universal/rule_engine-1.0/bin/rule_engine -Dconfig.file=$P 

For further explanation, I recommend this article, which explains the difference between ARG and ENV in a clear way:

As you can see from the above image, the ARG values are available only during the image build.