Environment variables

You can set environment variables in your container without altering the container image by using one of the options below.

You should verify Terminal > Integrated: Inherit Env is checked in settings or the variables you set may not appear in the Integrated Terminal. This setting is checked by default.

Option 1: Add individual variables

Depending on what you reference in devcontainer.json:

Dockerfile or image: Add the containerEnv property to devcontainer.json to set variables that should apply to the entire container or remoteEnv to set variables for VS Code and related sub-processes (terminals, tasks, debugging, etc.):
```
"containerEnv": {
    "MY_CONTAINER_VAR": "some-value-here",
    "MY_CONTAINER_VAR2": "${localEnv:SOME_LOCAL_VAR}"
},
"remoteEnv": {
    "PATH": "${containerEnv:PATH}:/some/other/path",
    "MY_REMOTE_VARIABLE": "some-other-value-here",
    "MY_REMOTE_VARIABLE2": "${localEnv:SOME_LOCAL_VAR}"
}
```
As this example illustrates, containerEnv can reference local variables and remoteEnv can reference both local and existing container variables.

Video: Modify PATH in a dev container

Docker Compose: Since Docker Compose has built-in support for updating container-wide variables, only remoteEnv is supported in devcontainer.json:

"remoteEnv": {
    "PATH": "${containerEnv:PATH}:/some/other/path",
    "MY_REMOTE_VARIABLE": "some-other-value-here",
    "MY_REMOTE_VARIABLE2": "${localEnv:SOME_LOCAL_VAR}"
}

As this example illustrates, remoteEnv can reference both local and existing container variables.

To update variables that apply to the entire container, update (or extend) your docker-compose.yml with the following for the appropriate service:

version: '3'
services:
  your-service-name-here:
    environment:
      - YOUR_ENV_VAR_NAME=your-value-goes-here
      - ANOTHER_VAR=another-value
     # ...

If you've already built the container and connected to it, run Dev Containers: Rebuild Container from the Command Palette (F1) to pick up the change. Otherwise run Dev Containers: Open Folder in Container... to connect to the container.

Option 2: Use an env file

If you have a large number of environment variables that you need to set, you can use a .env file instead.

First, create an environment file somewhere in your source tree. Consider this .devcontainer/devcontainer.env file:

YOUR_ENV_VAR_NAME=your-value-goes-here
ANOTHER_ENV_VAR_NAME=your-value-goes-here

Next, depending on what you reference in devcontainer.json:

Dockerfile or image: Edit devcontainer.json and add a path to the devcontainer.env :
```
"runArgs": ["--env-file",".devcontainer/devcontainer.env"]
```
Docker Compose: Edit docker-compose.yml and add a path to the devcontainer.env file relative to the Docker Compose file:
```
version: '3'
services:
  your-service-name-here:
    env_file: devcontainer.env
    # ...
```

docker compose will automatically pick up a file called .env in the folder containing the docker-compose.yml, but you can also create one in another location.

Video: Load variables from an .env file

10/29/2024