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In June this year, Jonathan Chan, a software developer reported that Docker Compose automatically reads from .env. Since other systems also access the same file for parsing and processing variables, this was creating some confusion resulting in breaking compatibility with other .env utilities.

Docker Compose has a “docker-compose.yml” config file used for deploying, combining, and configuring multiple multi-container Docker applications. The .env file is used for putting values in the “docker-compose.yml” file. In the .env file, the default environment variables are specified in the form of key-value pairs.

With the release of 1.24.0, the feature where Compose will no longer accept whitespace in variable names sourced from environment files. This matches the Docker CLI behavior. breaks compatibility with other .env utilities. Although my setup does not use the variables in .env for docker-compose, docker-compose now fails because the .env file does not meet docker-compose’s format,” Chan explains.

This is not the first time that this issue has been reported. Earlier this year, a user opened an issue on the GitHub repo. He described that after upgrading Compose to 1.24.0-rc1, its automatic parsing of .env file was failing. “I keep export statements in my .env file so I can easily source it in addition to using it as a standard .env. In previous versions of Compose, this worked fine and didn’t give me any issues, however with this new update I instead get an error about spaces inside a value,” he explained in his report.

As a solution, Chan has proposed, “I propose that you can specify an option to ignore the .env file or specify a different.env file (such as .docker.env) in the docker-compose.yml file so that we can work around projects that are already using the .env file for something else.

This sparked a discussion on Hacker News where users also suggested a few solutions. “This is the exact class of problem that docker itself attempts to avoid. This is why I run docker-compose inside a docker container, so I can control exactly what it has access to and isolate it. There’s a guide to do so here. It has the added benefit of not making users install docker-compose itself – the only project requirement remains docker,” A user commented.

Another user recommended, “You can run docker-compose.yml in any folder in the tree but it only reads the .env from cwd. Just CD into someplace and run docker-compose.

Some users also pointed out the lack of authentication mechanism in Docker Hub. “Docker Hub still does not have any form of 2FA. Even SMS 2FA would be something / great at this point. As an attacker, I would put a great deal of focus on attacking a company’s registries on Docker Hub. They can’t have 2FA, so the work/reward ratio is quite high,” a user commented. Others recommended to set up a time-based one-time password (TOTP) instead.

Check out the reported issue on the GitHub repository.

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