Does Kubernetes download Docker image automatically when i create a pod or should I use Docker pull manually to Download the image locally?
You do not need to run docker pull manually. The pod definition contains the image name to pull and Kubernetes will pull the image for you. You have several options in terms of defining how Kubernetes will decide to pull the image, using the imagePullPolicy: definition in your pod spec. Much of this is documented here, but basically you can pull if the image is not present, pull always, never update (once the image is local). Hopefully that doc can get you started.
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I am trying to run a docker image that I have build locally with Kubernetes.
Getting below error
Failed to pull image "myImage": rpc error: code = Unknown desc = Error response from daemon: pull access denied for myImage, repository does not exist or may require 'docker login'
In yaml file i have given as
image: myImage
imagePullPolicy: IfNotPresent
In local i am using docker-desktop and minikube.
I have tried multiple ways but only thing is working on to make tar of myImage and load in minikube.
I have tried using eval $(minikube docker-env) but after this my image is not able to build because it's pulling base image from organization nexus server.
Can anyone suggest anyother way?
Unfortunately I can't comment yet so I have to post an answer. The image you're trying to pull, myImage does not exist in the local image cache of your kubernetes cluster. Running a docker image ls command should yield a list of images that are available locally. If docker doesn't find an image locally, it will (by default) then go to Docker Hub to find the image. Seeing as the image listed has no prefix like someOrganization\ the image is assumed to be an officially published image from DockerHub themselves. Since your locally built image isn't an official Dockerhub image it doesn't know what to run. So the core of the problem is that your minikube doesn't have access to wherever you built your image. Unfortunately I haven't used minikube before so i'm unable to comment on any intricacies of how to work with it. I would be remiss if I left my answer like that, though, so looking at the docs for minikube ( REF: https://minikube.sigs.k8s.io/docs/handbook/pushing/#1-pushing-directly-to-the-in-cluster-docker-daemon-docker-env ) you're doing the right thing with the eval.
Sooo... your minikube isn't stock/vanilla and it pulls from a company repo? Sounds like you need to alter your minikube or you should re-evaluate the base image you're using and fix the Dockerfile.
To fix this, set imagePullPolicy to Never.
Ensure to set eval $(minikube docker-env) before building the image.
Maybe this is a little bit late but... if anyone has the same issue, here is how I solved something like this:
You need to pass "Never" as imagePullPolicy:
imagePullPolicy: Never
You need to load the image inside minikube:
minikube image load myImage
After all this, just continue as usual:
kubectl apply -f whereverTheFileIs.yaml
Let's say I have an image foo with tag v1.
So I deployed it on Kubernetes by foo:v1.
However, for some reason(e.g. monoversion in monorepo), I pushed the exact same image to container registry with tag v2.
And I changed k8s manifest to foo:v2.
In this situation, I want to update the pod only when the image digest of v1 and v2 are different. So in the case of foo, the digest are same, so container of foo:v1 should keep running.
Is this possible? If so, how?
Thanks
There is no way to update tag image without restarting pod.
The only way to make it work is too use digest explicitly instead of tags.
So now image spec would look like this:
spec:
image: foo#sha256:50cf965a6e08ec5784009d0fccb380fc479826b6e0e65684d9879170a9df8566
This way your image does not depended on tags. Digests can be found either on dockerhub or by running command docker images --digests <image-name>
I have a private registry and when I try to pull images I get a DNS lookup error. This is after following the steps provided in kubernetes documentation.
I just wanted to know what steps will kubernetes perform to pull the images from a container registry. Will the kubernetes master pull the images and deploy it in the nodes or is this also scheduled to the nodes to pull the required images
No, the master won't access your registry.
The nodes will pull the images when they need it (ie. when a pod that uses the images will be scheduled)
In your case, you must check that accessing the registry is possible from the nodes (you can try a manual docker pull for that)
If your registry needs some authentification, you will also have to add some credential in your namespaces secrets (but your "DNS lookup error" does tell that it is not your actual issue)
I load an image (.tar) into local docker repository and then Kubernetes pulls that Image into a container. After the application is up and running I want to remove that image from local docker repository, is that right way or Kubernetes still needs that image inside docker local repository?
I have tested when deleting that image, my Application still works, but if I want to scale up or scale down, I got a problem because the image is missing.
I presume, if the Pod goes down, Kubernetes will seek for Image again in docker repository?
Is there any way to cache that Image inside Kubernetes, so no need to pull again from docker repository?
The reason why I want to delete these images right after Application run on Kubernetes is security, I don't want to leave my images inside docker repository so a user can't extract that image and export it somewhere...
I presume, if the Pod goes down, Kubernetes will seek for Image again in docker repository?
Yes.
Is there any way to cache that Image inside Kubernetes, so no need to pull again from docker repository?
When you pull an image it's cached locally by docker or your runtime manager.
The reason why I want to delete these images right after Application run on Kubernetes is security, I don't want to leave my images inside docker repository so a user can't extract that image and export it somewhere...
If you are concerned about security you shouldn't put sensitive information in the image (passwords, credentials, keys). That's why there are Kubernetes Secrets or tools like Hashicorp Vault.
If you are concerned about keeping intellectual property private you should consider using a private container image repository or private Docker registry
Using Kubernetes for deployment:
Considering I have a Dockerfile, I build, then push to registry.
If I run a container on a host, the image gets pulled and the container is ran.
Now, if i update the Dockerfile, build and push again, without changing its tag then the image is changed in the registry, but the host has the image pulled, and it doesn't seem to go look for updates.
How do i force a pull to get the latest image when running a container?
I can manually pull the image, but I'd like to know if there is a 'formal way' of doing this (in the pod or rc templates?)
Thanks for insight.
Set an imagePullPolicy of Always on the container