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.
Tip
Don't use environment variables to pass sensitive information, such as passwords, in to your containers. Use secrets instead.
Use the environment
attribute
You can set environment variables directly in your container's environment with the
environment
attribute in your compose.yml
.
It supports both list and mapping syntax:
services:
webapp:
environment:
DEBUG: "true"
is equivalent to
services:
webapp:
environment:
- DEBUG=true
See
environment
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 ...
:web: environment: - DEBUG
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.web: environment: - DEBUG=${DEBUG}
Use the env_file
attribute
A container's environment can also be set using
.env
files along with the
env_file
attribute.
services:
webapp:
env_file: "webapp.env"
Using an .env
file lets you to 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.
The
env_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.yml
file.
Important
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.
- In addition, as the
.env
file supports interpolation, it is possible to combine those with values set byenvironment
. - As of Docker Compose version 2.24.0, you can set your
.env
file, defined by theenv_file
attribute, to be optional by using therequired
field. Whenrequired
is set tofalse
and the.env
file is missing, Compose silently ignores the entry.env_file: - path: ./default.env required: true # default - path: ./override.env required: false
- Values in your
.env
file can be overridden from the command line by usingdocker compose run -e
.
Set environment variables with docker compose run --env
Similar to docker run --env
, you can set environment variables temporarily with docker compose run --env
or its short form docker compose run -e
:
$ docker compose run -e DEBUG=1 web python console.py
Additional information
You can also pass a variable from the shell or your environment files by not giving it a value:
$ docker compose run -e DEBUG web python console.py
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.