1.inspecting_container_image.md

Inspecting containers

1. Clone locally kustomize project:

   git clone https://github.com/kubernetes-sigs/kustomize

   cd kustomize

2. Build the container image locally (add time as a prefix for Mac/Linux):

   KUSTOMIZE_DATE=$(date -u +'%Y-%m-%dT%H:%M:%SZ')

   docker build --build-arg="VERSION=v0.1.0" --build-arg="DATE=v0.0.1" --build-arg="DATE=$KUSTOMIZE_DATE" -t kustomize-local:0.1.0 -f kustomize.Dockerfile .

   Check the image size:

   docker image ls

   Check the artifact contents:

   docker history kustomize-local:0.1.0

3. Digests, manifests and immutable tags

   Kustomize image created locally doesn't have a digest:

   docker image ls --digests

   Image with manifest:

   docker image pull alpine:3.19.1

   docker manifest inspect alpine:3.19.1

   Pull with digest:

   docker image pull alpine@sha256:6457d53fb065d6f250e1504b9bc42d5b6c65941d57532c072d929dd0628977d0

4. Configuration

   docker save alpine:3.19.1 > alpine_3_19_1.tar

   mkdir alpine_3_19_1

   tar -xzvf alpine_3_19_1.tar -C alpine_3_19_1

   cd alpine_3_19_1

    manifest.json: reference to config file and layers files
   
    digest calculated from config file
   

5. Layers

   docker save kustomize-local:0.1.0 > kustomize_local_0_1_0.tar

   mkdir kustomize-local

   tar -xzvf kustomize_local_0_1_0.tar -C kustomize-local

   Untar a layer and check its content

   cd kustomize-local/a99f89fe89f30e24c9cef7b8d6c6cbde16bc74aef975ccd1e832873aa5e0d252

   mkdir layer

   tar -xzvf layer.tar -C layer

   ./layer/app/kustomize