List container images in Kubernetes cluster with SIZE (like docker image ls)

Question

In the Kubernetes documentation List All Container Images Running in a Cluster we can list all containers by:

kubectl get pods --all-namespaces -o jsonpath="{..image}" |\
tr -s '[[:space:]]' '\n' |\
sort |\
uniq -c

Here is an example of output:

  1 cdkbot/addon-resizer-amd64:1.8.1
  1 cdkbot/hostpath-provisioner-amd64:1.0.0
  1 cdkbot/registry-amd64:2.6
  1 coredns/coredns:1.6.6
  1 docker.io/cdkbot/addon-resizer-amd64:1.8.1
  1 docker.io/cdkbot/hostpath-provisioner-amd64:1.0.0
  1 docker.io/cdkbot/registry-amd64:2.6
  1 docker.io/coredns/coredns:1.6.6
  1 docker.io/grafana/grafana:6.4.3
  2 docker.io/istio/citadel:1.5.1
  2 docker.io/istio/examples-bookinfo-details-v1:1.15.0
  2 docker.io/istio/examples-bookinfo-productpage-v1:1.15.0
  2 docker.io/istio/examples-bookinfo-ratings-v1:1.15.0
  2 docker.io/istio/examples-bookinfo-reviews-v1:1.15.0
  2 docker.io/istio/examples-bookinfo-reviews-v2:1.15.0
  2 docker.io/istio/examples-bookinfo-reviews-v3:1.15.0
  2 docker.io/istio/galley:1.5.1
  4 docker.io/istio/kubectl:1.5.1
  4 docker.io/istio/mixer:1.5.1
  2 docker.io/istio/pilot:1.5.1
 34 docker.io/istio/proxyv2:1.5.1
  2 docker.io/istio/sidecar_injector:1.5.1
  2 docker.io/jaegertracing/all-in-one:1.16
  1 docker.io/kubernetesui/dashboard:v2.0.0
  1 docker.io/kubernetesui/metrics-scraper:v1.0.4
  2 docker.io/library/nginx:latest
  2 docker.io/prom/prometheus:v2.12.0
  1 docker.io/radial/busyboxplus:curl
  1 grafana/grafana:6.4.3
  2 k8s.gcr.io/metrics-server-amd64:v0.2.1
  1 kubernetesui/dashboard:v2.0.0
  1 kubernetesui/metrics-scraper:v1.0.4
  2 nginx
  2 quay.io/kiali/kiali:v1.9
  1 radial/busyboxplus:curl

Unfortunately the size of the docker image is missing. Is there a way to get the container image size? Pretty much like docker image ls. Copy of the output from this example for convenience:

$ docker image ls
REPOSITORY                  TAG                 IMAGE ID            CREATED             SIZE
docker.io/ubuntu            latest              3556258649b2        7 days ago          64.2 MB
docker.io/alpine            latest              b7b28af77ffe        2 weeks ago         5.58 MB
docker.io/centos            latest              9f38484d220f        4 months ago        202 MB
docker.io/hello-world       latest              fce289e99eb9        7 months ago        1.84 kB

Answer 1

If you have the correct permissions, get the nodes not the pods.

kubectl get nodes -o json | jq '.items[].status.images[] | .names[1], .sizeBytes'

Answer 2

On my k8s system kubectl describe pod ABC doesn't show the image size, but you can create a script that:

1. gets the name of the image (I assuming you have one container in the pod, otherwise the script will be slightly more complicated depending on what you want to print actually)
2. runs docker image ls on the same machine. This assumes that you actually have that docker image on the machine you're running this command.
3. You slight format the output of that command to "catch" the image size

All-in-all it looks like this:

docker image ls `kubectl get pod YOUR_POD_NAME_GOES_HERE  -o jsonpath='{.spec.containers[0].image}'` --format='{{println .Size}}'

Answer 3

Kubernetes doesn't provide image size information in its outputs. Even though we able to get a list of images running in a cluster, it is not a straight forward process to get the size of an image in a multi-node cluster. But in such cases where we run a single node cluster, we could achieve this by running a docker or DinD (Docker in Docker) container in Kubernetes cluster. Still, it is a good approach for testing purposes only. I have nothing to say about running this on critical environments. It depends.

Spin up a pod by mounting host's /var/lib/docker.sock file inside and exec as shown below.

apiVersion: v1
kind: Pod
metadata:
  labels:
    run: dind
  name: dind
spec:
  containers:
  - image: docker:dind
    name: dind
    command: ["cat"]
    tty: true
    resources: {}
    volumeMounts:
    - mountPath: /var/run/docker.sock
      name: docker
      readOnly: true
  volumes:
  - name: docker
    hostPath:
      path: /var/run/docker.sock
      type: File
  dnsPolicy: ClusterFirst
  restartPolicy: Never
status: {}

---

$ kubectl exec -i dind -n dev sh -- docker images nginx 
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
nginx               latest              4571e56e27f0        11 hours ago        132MB

$kubectl exec -i dind -n dev sh -- docker image ls
REPOSITORY                                                       TAG                 IMAGE ID            CREATED             SIZE
nginx                                                            latest              4571e56e27f0        21 hours ago        132MB