Access .env variables in Dockerfile

[sevab]

I'm trying to access .env variables as part of my Docker build process in the Dockerfile, e.g.

in .env I have

AWS_ACCESS_KEY_ID=...
AWS_SECRET_ACCESS_KEY=...

As per the documentation, I then expose them to the builder like so in deploy.yml:

builder:
  cache:
    type: registry
  secrets:
    - AWS_ACCESS_KEY_ID
    - AWS_SECRET_ACCESS_KEY

but when I try to access them in the Dockerfile:

ARG AWS_ACCESS_KEY_ID
ENV AWS_ACCESS_KEY_ID=${AWS_ACCESS_KEY_ID}
ARG AWS_SECRET_ACCESS_KEY
ENV AWS_SECRET_ACCESS_KEY=${AWS_SECRET_ACCESS_KEY}
RUN aws s3 sync ....

They aren't accessible (in my case aws s3 sync breaks with fatal error: Unable to locate credentials).

Anybody can point out how to access .env vars in Dockerfile?

[sevab]

My bad, I'm new to Docker secrets, got it all working:

RUN --mount=type=secret,id=AWS_ACCESS_KEY_ID \
    --mount=type=secret,id=AWS_SECRET_ACCESS_KEY \
    AWS_ACCESS_KEY_ID=$(cat /run/secrets/AWS_ACCESS_KEY_ID) \
    AWS_SECRET_ACCESS_KEY=$(cat /run/secrets/AWS_SECRET_ACCESS_KEY) \
    aws s3 sync ....

[koenhandekyn]

lost some time as i also missed the mount part of the documentation. maybe it could be highlighted in the docs ;)