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