Remotely re-tagging a Docker image

::: lead tl;dr: docker buildx imagetools create $SOURCE --tag $TARGET :::

• Some managed app platform provides the ability to deploy images simply by pushing a Docker image to a predefined tag.

• For example, DigitalOcean’s App Platform has this option:

  

• Usually one might do a docker pull && docker push in a deployment pipeline, but it’s a waste of bandwidth:

  SOURCE=registry.tld/service:commit-abcdef
  TARGET=registry.tld/service:staging
  
  docker pull $SOURCE
  docker tag $SOURCE $TARGET
  docker push $TARGET

  • Also, if the image is multi-platform, only the current platform will be retagged. This may be problematic if your CI runs on Intel but the deployment target runs on ARM e.g. Ampere or Graviton.

  • On some registries, they provide a CLI command to re-tag an image, but it’s specific to that platform. e.g. Amazon ECR, GCR.

• Thanks to Francois Nel’s StackOverflow answer on the question “Add remote tag to a docker image”, now I know we can do this:

  SOURCE=registry.tld/service:commit-abcdef
  TARGET=registry.tld/service:staging
  
  docker buildx imagetools create $SOURCE --tag $TARGET

  And it supports multi-platform images!