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I am using kops as kubernetes deployment.
I noticed that whenever an image with same tag number is entered in deployment file the system takes the previous image if imagepullpolicy is not set to always
Is there any way in which I can see all the cached images of a container in kubernetes environment ?
Like suppose I have an image test:56 currently running in a deployment and test:1 to test:55 were used previously, so does kubernetes cache those images ? and if yes where can those be found ?
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Kubernetes itself doesn't cache the images, it is the underlying OCI runtime that does the caching.
The concept of Docker images comes with immutable layers. Every command you execute results in a new layer that contains the changes compared to the previous layer. All previously built layers are cached and can be reused.
If you use the default storage driver overlay2, then your Docker images are stored in /var/lib/docker/overlay2 . There, you can find different files that represent read-only layers of a Docker image and a layer on top of it that contains your changes.
I noticed that whenever an image with same tag number is entered in deployment file the system takes the previous image if
imagepullpolicyis not set toalways
A pre-pulled image can be used to preload certain images for speed or as an alternative to authenticating to a private registry, optimizing performance.
The docker will always cache all images that were used locally.
Since you are using EKS, keep in mind that if you have node health management (meaning a node will be replaced if it fails) the new node won't have the images cached from the old one so it's always a good idea to store your images on a Registry like your Cloud Provider Registry or a local registry.
Is there any way in which I can see all the cached images of a container in kubernetes environment ?
Yes, you must use docker images to list the images stored in your environment.
Like suppose I have an image
test:56currently running in a deployment andtest:1totest:55were used previously, so does Kubernetes cache those images ? and if yes where can those be found ?
I prepared an example for you:
$ kubectl run busy284 --generator=run-pod/v1 --image=busybox:1.28.4
pod/busy284 created
$ kubectl run busy293 --generator=run-pod/v1 --image=busybox:1.29.3
pod/busy284 created
$ kubectl run busy284 --generator=run-pod/v1 --image=busybox:1.28
pod/busy28 created
$ kubectl run busy284 --generator=run-pod/v1 --image=busybox:1.29
pod/busy29 created
$ kubectl run busy284 --generator=run-pod/v1 --image=busybox:1.30
pod/busy284 created
$ kubectl run busybox --generator=run-pod/v1 --image=busybox
pod/busybox created
Now let's check the images stored in docker images
$ docker images
REPOSITORY TAG IMAGE ID CREATED SIZE
k8s.gcr.io/kube-proxy v1.17.3 ae853e93800d 5 weeks ago 116MB
k8s.gcr.io/kube-controller-manager v1.17.3 b0f1517c1f4b 5 weeks ago 161MB
k8s.gcr.io/kube-apiserver v1.17.3 90d27391b780 5 weeks ago 171MB
k8s.gcr.io/kube-scheduler v1.17.3 d109c0821a2b 5 weeks ago 94.4MB
kubernetesui/dashboard v2.0.0-beta8 eb51a3597525 3 months ago 90.8MB
k8s.gcr.io/coredns 1.6.5 70f311871ae1 4 months ago 41.6MB
k8s.gcr.io/etcd 3.4.3-0 303ce5db0e90 4 months ago 288MB
kubernetesui/metrics-scraper v1.0.2 3b08661dc379 4 months ago 40.1MB
busybox latest 83aa35aa1c79 10 days ago 1.22MB
busybox 1.30 64f5d945efcc 10 months ago 1.2MB
busybox 1.29 758ec7f3a1ee 15 months ago 1.15MB
busybox 1.29.3 758ec7f3a1ee 15 months ago 1.15MB
busybox 1.28 8c811b4aec35 22 months ago 1.15MB
busybox 1.28.4 8c811b4aec35 22 months ago 1.15MB
You can see all the pushed images listed.
It's good to clean old resources from your system using the command docker system prune to free space on your server from time to time.
If you have any doubt, let me know in the comments.
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