Set environment variables (original) (raw)

Set environment variables within your container's environment

A container's environment is not set until there's an explicit entry in the service configuration to make this happen. With Compose, there are two ways you can set environment variables in your containers with your Compose file.

Don't use environment variables to pass sensitive information, such as passwords, in to your containers. Use secrets instead.

You can set environment variables directly in your container's environment with theenvironment attribute in your compose.yaml.

It supports both list and mapping syntax:

is equivalent to

Seeenvironment attribute for more examples on how to use it.

Additional information

You can choose not to set a value and pass the environment variables from your shell straight through to your containers. It works in the same way as docker run -e VARIABLE ...:

The value of the DEBUG variable in the container is taken from the value for the same variable in the shell in which Compose is run. Note that in this case no warning is issued if the DEBUG variable in the shell environment is not set.

You can also take advantage of interpolation. In the following example, the result is similar to the one above but Compose gives you a warning if the DEBUG variable is not set in the shell environment or in an .env file in the project directory.

A container's environment can also be set using .env files along with theenv_file attribute.

Using an .env file lets you use the same file for use by a plain docker run --env-file ... command, or to share the same .env file within multiple services without the need to duplicate a long environment YAML block.

It can also help you keep your environment variables separate from your main configuration file, providing a more organized and secure way to manage sensitive information, as you do not need to place your .env file in the root of your project's directory.

Theenv_file attribute also lets you use multiple .env files in your Compose application.

The paths to your .env file, specified in the env_file attribute, are relative to the location of your compose.yaml file.

Interpolation in .env files is a Docker Compose CLI feature.

It is not supported when running docker run --env-file ....

Additional information

If multiple files are specified, they are evaluated in order and can override values set in previous files.
As of Docker Compose version 2.24.0, you can set your .env file, defined by the env_file attribute, to be optional by using the required field. When required is set to false and the .env file is missing, Compose silently ignores the entry.
As of Docker Compose version 2.30.0, you can use an alternative file format for the env_file with the format attribute. For more information, seeformat.
Values in your .env file can be overridden from the command line by using docker compose run -e.

Similar to docker run --env, you can set environment variables temporarily with docker compose run --env or its short form docker compose run -e:

Additional information

You can also pass a variable from the shell or your environment files by not giving it a value:

The value of the DEBUG variable in the container is taken from the value for the same variable in the shell in which Compose is run or from the environment files.