Docker build ignores my .env file. What am I missing?

Question

I have a `.env` in the project root but `process.env.DATABASE_URL` is undefined inside the container. `docker build .` and then `docker run my-app`.

Daniel Kim · Accepted Answer

`.env` files aren't read automatically by `docker run`, and you shouldn't bake secrets into the image anyway. Pass them at runtime:

```bash
docker run --env-file .env my-app
```

With Compose, use `env_file: .env` on the service. Also check `.dockerignore` lists `.env` so it never ends up in the image.

Liam O'Brien · Answer

And never `COPY .env` in the Dockerfile. Anyone who pulls the image can read it.

2 Answers