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docker-script-find-latest-image-tag

(Over complicated) Bash script to find the version of a Docker image you are running when you took a shortcut and used "latest".
Now you don't know what image version was previously working, and a breaking change happened..

docker images shows image:<none> or image:latest. What image version am I using?

Tag your images, and never use latest!

This script checks your local image's ID against every tag of an image in Docker Hub.

Some issues to note:
Issue #1: If the image no longer exists on the Docker Registry. You obviously won't find it.
Issue #2: The script doesn't work for Windows images. There are no manifests available for those.

If you're lucky you can find the version tag

Trick #1

If you're lucky, the image's label will have the version. With a little jq magic you can get the good bits.

$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
traefik             latest              96c63a7d3e50        2 months ago        85.7MB

$ IMAGE_ID=96c63a7d3e50

$ docker image inspect --format '{{json .}}' "$IMAGE_ID" | jq -r '. | {Id: .Id, Digest: .Digest, RepoDigests: .RepoDigests, Labels: .Config.Labels}'

Output:

{
  "Id": "sha256:96c63a7d3e502fcbbd8937a2523368c22d0edd1788b8389af095f64038318834",
  "Digest": null,
  "RepoDigests": [
    "traefik@sha256:5ec34caf19d114f8f0ed76f9bc3dad6ba8cf6d13a1575c4294b59b77709def39"
  ],
  "Labels": {
    "org.opencontainers.image.description": "A modern reverse-proxy",
    "org.opencontainers.image.documentation": "https://docs.traefik.io",
    "org.opencontainers.image.title": "Traefik",
    "org.opencontainers.image.url": "https://traefik.io",
    "org.opencontainers.image.vendor": "Containous",
    "org.opencontainers.image.version": "v1.7.20"
  }
}

Trick #2

Pull a bunch of images and hope the Image ID matches. Not much to this trick..

If you are unlucky, continue on..

Requirements

  • Docker or Podman
  • curl
  • jq
  • sed
  • tr
  • grep
  • sort
  • wc

Usage

./docker_image_find_tag.sh -h
Usage:
./docker_image_find_tag.sh [-n image name] [-i image-id]
Example: ./docker_image_find_tag.sh -n traefik -i 96c63a7d3e50 -f 1.7
  -n [text]: Image name (Required). '-n traefik' would reference the traefik image
  -i [text]: Image ID. Required if Image ID (Long) (-L) is ommited.
             Found in 'docker images'. Can also use -i image:tag
  -L [text]: Image ID (Long). Required if Image ID (-i) is ommited
      Example: -L sha256:96c63a7d3e502fcbbd8937a2523368c22d0edd1788b8389af095f64038318834
      To find, it is Id from:
      docker image inspect --format '{{json .}}' IMAGE_ID | jq -r '. | {Id: .Id, Digest: .Digest, RepoDigests: .RepoDigests, Labels: .Config.Labels}'
  -D: Use Docker binary for Image ID check (Default) (Optional)
  -P: Use Podman binary for Image ID check (Optional)
  -r [text]: Registry URL to use. Example: -r https://index.docker.io/v2 (Default) (Optional)
  -a [text]: Registry AUTH to use. Example: -a https://auth.docker.io (Default) (Optional)
  -l [number]: Tag limit. Defaults to 100. (Optional)
  -f [text]: Filter tag to contain this value (Optional)
  -v: Verbose output (Optional)

Usage Example

# ./docker_image_find_tag.sh -n traefik -i 96c63a7d3e50 -f 1.7. -l 10 -v

Using IMAGE_NAME: traefik
Using REGISTRY: https://index.docker.io/v2
Found Image ID Source: sha256:96c63a7d3e502fcbbd8937a2523368c22d0edd1788b8389af095f64038318834
Found Total Tags: 610
Found Tags (after filtering): 178
Limiting Tags to: 10
Limit reached, consider increasing limit (-l [number]) or use more specific filter (-f [text])

Found Tags:
v1.7.21-alpine
v1.7.21
v1.7.20-alpine
v1.7.20
v1.7.19-alpine
v1.7.19
v1.7.18-alpine
v1.7.18
v1.7.17-alpine
v1.7.17

Checking for image match..
Found match. tag: v1.7.20
Image ID Target: sha256:96c63a7d3e502fcbbd8937a2523368c22d0edd1788b8389af095f64038318834
Image ID Source: sha256:96c63a7d3e502fcbbd8937a2523368c22d0edd1788b8389af095f64038318834

This example is searching for an image named traefik, with an image ID of 96c63a7d3e50 (which we got from running the command docker images.

The total number of tags for traefik images is 610! You could use this script to check every one, but that will take a minute or two. Instead, you can filter the results a bit. I think I’m running something in version 1.7.x. I’m also limiting the search to 10 tags in this example to keep the output small.