Skip to main content

Environment Variables

To set environment variables for you project, you can use the CLI commands:

disco env:set --project my-project VAR_NAME=value

You can set many of them at once:

disco env:set --project my-project VAR_NAME=value OTHER_VAR="other value"

To retrieve a specific value:

disco env:get --project my-project VAR_NAME

Or to retrieve all key/values:

disco env:list --project my-project

Using Environment Variables in your App​

Your code can use environment variables like anywhere else.

E.g. in Bash

echo "Hello $VAR_NAME"

in Python

import os
print(f"Hello {os.getenv('VAR_NAME')")

or in JavaScript with NodeJS

console.log(`Hello ${process.env.VAR_NAME}`)

Using Environment Variables When Building Images​

When building Docker images, we need to be careful to avoid including the variables in the images. disco uses the recommended way to expose environment variables without baking them into the images.

See Docker documentation about Build Secrets for more info.

Dot Env (.env)​

You can either access all of the variables as a .env file, where each line is VAR_NAME=value

RUN --mount=type=secret,id=.env your-command

Docker will make the file available as /run/secrets/.env for that one command. If the base image you're using supports it, you could use the .env file as follows

RUN --mount=type=secret,id=.env env $(cat /run/secrets/.env | xargs) your-command

That way, your-command will have the environment loaded just before it runs.

Make sure to not set the environment variable with export, because it would set it in the environment of the image and it would mean your secrets have leaked.

Individual Variable​

If you only want access to a single variable, you can do this

RUN --mount=type=secret,id=VAR_NAME your-command

and /run/secrets/VAR_NAME will contain the value of the variable.

You could add many variables using this method:

RUN --mount=type=secret,id=VAR_NAME --mount=type=secret,id=OTHER_VAR your-command

Specifying the File Path and File Name to Use​

If you need to use a specific path for the files that Docker makes available, instead of e.g. /run/secrets/.env, you can specify it with target.

The Docker documentation contains this example

RUN --mount=type=secret,id=aws,target=/root/.aws/credentials \
    aws s3 cp ...

We can adapt it to disco's environment variables like

disco env:set --projecct my-project AWS_CREDENTIALS='...'
RUN --mount=type=secret,id=AWS_CREDENTIALS,target=/root/.aws/credentials \
    aws s3 cp ...