How to get Dockerfile or last CMD/ENTRYPOINT of a kubernetes deployment image?

Question

So I have a deployment like this:

apiVersion: v1
kind: Pod
metadata:
  name: yy
spec:
  containers:
    - name: yy
      image: gcr.io/xx/yy
  imagePullSecrets:
    - name: gcr-json-key

That CrashLoopBackOff on Minikube, I know the issue, that the ENTRYPOINT need to be overriden before use, how can I know what's the original CMD/ENTRYPOINT of that image?

Answer 1

If you're running docker, pull the image and inspect it with:

docker pull gcr.io/xx/yy
docker image inspect gcr.io/xx/yy

Without docker, some registries allow you to explore the images. And there are online tools like https://explore.ggcr.dev (drill down into the config digest).

There are also commands to interact with registries, including crane (from Google), skopeo (from Redhat), and regclient/regctl (from me). Here's the regctl example:

$ regctl image inspect ghcr.io/regclient/regsync:latest
{
  "created": "2023-02-26T02:37:17Z",
  "architecture": "amd64",
  "os": "linux",
  "config": {
    "User": "appuser",
    "Env": [
      "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
    ],
    "Entrypoint": [
      "/regsync"
    ],
    "WorkingDir": "/",
...

Answer 2

I found out how:

minikube image save gcr.io/xx/yy /tmp/a.tar

then open that /tmp/a.tar using any decompressor and look for the .json file to know the entrypoint or cmd.

Not sure how to do this with real remote kubernetes though.