Runtime Variables Configuration for Static Frontend Apps in a Docker Image Promotion Workflow

Deploying the same Docker Image from staging to production is common when using container-based deployments. Docker Image Promotion is an approach to using Docker Image that have been built, tested, and verified for use in different environments such as staging, test, and production without needing to re-build at each step. Docker Image Promotion ensures consistent behavior between environments, so that the image that has been previously built and tested is the image that is deployed to production. Apart from that, image promotion will also cut deployment time shorter by not doing a rebuild; for example, if the build is carried out at the deployment to staging stage, then when we want to deploy to production, we only need to "promote" the Docker Image, and not do a rebuild. Root of the problem We need to know that ARG / --build-arg is only available during build time on the image and ENV / --env is available during build time and runtime on the image. This means, if we have an environm