discover the image cache

• image layers
• union file system
• history and inspect commands
• copy on write

image layers

docker image history <image_name>

• all images start with "scratch"
• each layer gets a unique "sha" (sha256)
• don't need to download layers we already have in cache
• never storing multiple image layers

view image metadata

docker image inspect <image_name>

image tagging and pushing

• image id vs tag
• image don't have a "name"
  • repository / tag / image id
• tag is not quite a 'version'
• tagging an image

  docker image tag <source_image>[:tag] <target_name>[:tag]