mirror of https://github.com/docker/docs.git
124 lines
4.8 KiB
Markdown
124 lines
4.8 KiB
Markdown
---
|
||
description: How to set, use and manage environment variables in Compose
|
||
keywords: fig, composition, compose, docker, orchestration, environment, variables, env file
|
||
title: Environment variables in Compose
|
||
---
|
||
|
||
There are multiple parts of Compose that deal with environment variables in one sense or another. This page should help you find the information you need.
|
||
|
||
|
||
## Substituting environment variables in Compose files
|
||
|
||
It's possible to use environment variables in your shell to populate values inside a Compose file:
|
||
|
||
web:
|
||
image: "webapp:${TAG}"
|
||
|
||
For more information, see the [Variable substitution](compose-file.md#variable-substitution) section in the Compose file reference.
|
||
|
||
|
||
## Setting environment variables in containers
|
||
|
||
You can set environment variables in a service's containers with the ['environment' key](compose-file.md#environment), just like with `docker run -e VARIABLE=VALUE ...`:
|
||
|
||
web:
|
||
environment:
|
||
- DEBUG=1
|
||
|
||
|
||
## Passing environment variables through to containers
|
||
|
||
You can pass environment variables from your shell straight through to a service's containers with the ['environment' key](compose-file.md#environment) by not giving them a value, just like with `docker run -e VARIABLE ...`:
|
||
|
||
web:
|
||
environment:
|
||
- DEBUG
|
||
|
||
The value of the `DEBUG` variable in the container will be taken from the value for the same variable in the shell in which Compose is run.
|
||
|
||
|
||
## The “env_file” configuration option
|
||
|
||
You can pass multiple environment variables from an external file through to a service's containers with the ['env_file' option](compose-file.md#envfile), just like with `docker run --env-file=FILE ...`:
|
||
|
||
web:
|
||
env_file:
|
||
- web-variables.env
|
||
|
||
|
||
## Setting environment variables with 'docker-compose run'
|
||
|
||
Just like with `docker run -e`, you can set environment variables on a one-off container with `docker-compose run -e`:
|
||
|
||
docker-compose run -e DEBUG=1 web python console.py
|
||
|
||
You can also pass a variable through from the shell by not giving it a value:
|
||
|
||
docker-compose run -e DEBUG web python console.py
|
||
|
||
The value of the `DEBUG` variable in the container will be taken from the value for the same variable in the shell in which Compose is run.
|
||
|
||
|
||
## The “.env” file
|
||
|
||
You can set default values for any environment variables referenced in the Compose file, or used to configure Compose, in an [environment file](env-file.md) named `.env`:
|
||
|
||
$ cat .env
|
||
TAG=v1.5
|
||
|
||
$ cat docker-compose.yml
|
||
version: '3'
|
||
services:
|
||
web:
|
||
image: "webapp:${TAG}"
|
||
|
||
When you run `docker-compose up`, the `web` service defined above uses the image `webapp:v1.5`. You can verify this with the [config command](reference/config.md), which prints your resolved application config to the terminal:
|
||
|
||
$ docker-compose config
|
||
version: '3'
|
||
services:
|
||
web:
|
||
image: 'webapp:v1.5'
|
||
|
||
Values in the shell take precedence over those specified in the `.env` file. If you set `TAG` to a different value in your shell, the substitution in `image` uses that instead:
|
||
|
||
$ export TAG=v2.0
|
||
$ docker-compose config
|
||
version: '3'
|
||
services:
|
||
web:
|
||
image: 'webapp:v2.0'
|
||
|
||
When values are provided with both with shell `environment` variable and with an `env_file` configuration file, values of environment variables will be taken **from environment key first and then from environment file, then from a `Dockerfile` `ENV`–entry**:
|
||
|
||
$ cat ./Docker/api/api.env
|
||
NODE_ENV=test
|
||
|
||
$ cat docker-compose.yml
|
||
version: '3'
|
||
services:
|
||
api:
|
||
image: 'node:6-alpine'
|
||
env_file:
|
||
- ./Docker/api/api.env
|
||
environment:
|
||
- NODE_ENV=production
|
||
|
||
You can test this with for e.g. a _NodeJS_ container in the CLI:
|
||
|
||
$ docker-compose exec api node
|
||
> process.env.NODE_ENV
|
||
'production'
|
||
|
||
Having any `ARG` or `ENV` setting in a `Dockerfile` will evaluate only if there is _no_ Docker _Compose_ entry for `environment` or `env_file`.
|
||
|
||
_Spcecifics for NodeJS containers:_ If you have a `package.json` entry for `script:start` like `NODE_ENV=test node server.js`, then this will overrule _any_ setting in your `docker-compose.yml` file.
|
||
|
||
## Configuring Compose using environment variables
|
||
|
||
Several environment variables are available for you to configure the Docker Compose command-line behaviour. They begin with `COMPOSE_` or `DOCKER_`, and are documented in [CLI Environment Variables](reference/envvars.md).
|
||
|
||
## Environment variables created by links
|
||
|
||
When using the ['links' option](compose-file.md#links) in a [v1 Compose file](compose-file.md#version-1), environment variables will be created for each link. They are documented in the [Link environment variables reference](link-env-deprecated.md). Please note, however, that these variables are deprecated - you should just use the link alias as a hostname instead.
|