How to provide user defined argument and value in docker run?

Question

I want to achieve something like docker run --delay=

I could provide the value for delay using ENTRYPOINT AND CMD without providing argument in docker run but could not find a way to do from docker run.

In short, I want to know how to pass user defined argument and value to docker run command or using dockerfile

Answer 1

You can achieve it using environment variable. There are two ways to set environment variable.

• In Dockerfile -> You can set as follows. Detailed Explanation at https://docs.docker.com/engine/reference/builder/#env

  ENV <key> = <value>

• In docker run command -> You can set using -e flag. Detailed Explanation at https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e-env-env-file

  docker run -e <key> = <value> <image_name>

Answer 2

There are multiple ways to do that but I would recommend to go with environment variables. Just define the variable while running docker run and use it in your ENTRYPOINT script.

docker run -e DELAY=30 IMAGE [COMMAND] [ARG...]

Afterward use it in your ENTRYPOINT script as:

!#/bin/bash

# Play with $DELAY
echo $DELAY

# Start the root process
exec root_process_command

I hope it help!