fly deploy \
--build-secret RAILS_MASTER_KEY_SECRET="${RAILS_MASTER_KEY_PROD}" \
--dockerfile Dockerfile.production
Note: replace RAILS_MASTER_KEY_PROD
below with your env var.
BUILDKIT_PROGRESS=plain docker build \
--no-cache \
--secret id=RAILS_MASTER_KEY_SECRET,env=RAILS_MASTER_KEY_PROD \
--build-arg TARGET_RAILS_ENV="production" \
--build-arg RAILS_MASTER_KEY=$RAILS_MASTER_KEY_PROD \
-f Dockerfile.production \
"."