pass arguments in dockerfile?

Question

I want to pass an argument to my dockerfile such that I should be able to use that argument in my run command but it seems I am not able to do so

I am using a simple bash file that will trigger the docker build and docker run

FROM openjdk:8 AS SCRATCH WORKDIR / ADD . . RUN apt install unzip RUN unzip target/universal/rule_engine-1.0.zip -d target/universal/rule_engine-1.0 COPY target/universal/rule_engine-1.0 . ENV MONGO_DB_HOST="host.docker.internal" ENV MONGO_DB_PORT="27017" EXPOSE 9000 ARG path CMD target/universal/rule_engine-1.0/bin/rule_engine -Dconfig.file=$path

above is my dockerfile and below is my bash file which will access this dockerfile

#!/bin/bash # change the current path to rule engine path cd /Users/zomato/Documents/Intern_Project/rule_engine sbt dist ENVIR=$1 config="" if [ $ENVIR == "local" ] then config=conf/application.conf elif [ $ENVIR == "staging" ] then config=conf/staging.conf else config=conf/production.conf fi echo $config docker build --build-arg path=$config -t rule_engine_zip . docker run -i -t -p 9000:9000 rule_engine_zip

but when i access the dockerfile through bash script which will set config variable I am not able to set path variable in last line of dockerfile to the value of config.

Anything you pass in an ARG is compiled into the image – think of docker build as similar to sbt dist in your setup. If you can update your application to look for the file location in an environment variable rather than a Java property, then you can pass the location using the docker run -e option, without rebuilding the image. — David Maze
– David Maze, Commented Mar 10, 2021 at 10:36
Hi @William Martens i don't think this is the problem I am facing which you mentioned in your comment. thanks btw — Lazy_Nerd
– Lazy_Nerd, Commented Mar 10, 2021 at 11:53
Hi @David Maze thanks for sharing your Knowledge. I will try this — Lazy_Nerd
– Lazy_Nerd, Commented Mar 10, 2021 at 11:55

Maroun · Accepted Answer · 2021-03-14 07:50:12Z

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.

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