Accessing Environment Variables in a linked Docker

Question

How do I access the environment variables of a source container from another container which is linking to it with the --link argument? The docker manual states:

Environment Variables

Docker creates several environment variables when you link containers. Docker automatically creates environment variables in the target container based on the --link parameters. It will also expose all environment variables originating from Docker from the source container. These include variables from:

the ENV commands in the source container's Dockerfile

the -e, --env and --env-file options on the docker run command when the source container is started

http://docs.docker.com/userguide/dockerlinks/

But I can't access an environment variable which I set with

ENV MY_VARIABLE = "example"

in the linking container with

#!/bin/sh
echo $MY_VARIABLE

it will contain no value.

white_gecko · Accepted Answer · 2015-05-15 12:59:31Z

2

Environment variables from the source container are prefixed with the alias set with the --link <source container>:<alias> in the target container:

$<alias>_ENV_<env variable>

The environment variable will be accessible as follows if <alias> is e.g. set to source:

#!/bin/sh
echo $SOURCE_ENV_MY_VARIABLE

answered May 15, 2015 at 12:59

white_gecko

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