How to use export command to set environment variable with docker exec?

Question

I have a running docker container using an ancestor my_base_image. Now when the container is running, can I set an environment variable using export command with docker exec? if yes, how?

I tried using the following, but doesn't work

docker exec -i -t $(docker ps -q --filter ancestor=`my_base_image`) bash -c "export my_env_var=hey"

Basically I want to set my_env_var=hey as env variable inside docker container. I know this can be done in may ways using .env_file or env key docker-compose & ENV in Dockerfile. But I just want to know if it is possible using docker exec command

David Maze · Accepted Answer · 2019-10-31 17:45:51Z

3

This is impossible. A process can never change the environment of any other process beyond itself, except that it can specify the initial environment of processes it starts itself. In this case, your docker exec shell isn’t launching the main container process, so it can’t change that process’s environment variables.

This is one of a number of changes that you will need to stop, delete, and recreate the container for. You should treat this as extremely routine container maintenance and plan to delete the container eventually. That means, for example, keeping any data that needs to be persisted outside the container, ideally in an external database but possibly in a mounted volume.

answered Oct 31, 2019 at 17:45

David Maze

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2 Comments

rokpoto.com Over a year ago

what about entering the container with exec -it and exporting env. vars in the shell?

David Maze Over a year ago

That will affect that shell and nothing else. docker exec really shouldn’t be part of your core workflow, especially for configuration changes like this.

Lovelin B · Accepted Answer · 2023-04-18 16:03:14Z

0

use the -e or --env paramenter to pass environment variable for current session.

docker exec -it -e VAR=<value> <image> <command>

answered Apr 18, 2023 at 16:03

Lovelin B

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