Tips to Reduce Docker Images

• Docker uses layering when building Docker images, which means the next layer is basically the delta (add/remove/modify) from the previous layer. Therefore:
  • Even when a layer deletes a big file from previous layer, it still exists in the image but just not accessible to the user. This means the size of the image includes the big file.
  • Every time a layer changes, all the layers after it should change. This means when building new image, Docker mayn’t be able to use cached layers due to the changes in previous layers. Therefore, start first with layers that aren’t expected to change much and keep the last layers for things that may change more frequently.
• Build the Docker image using multi-stage build to avoid having multiple build tools that are not needed in the application in the image.