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Hello, I have a quick question how to properly upgrade an AKS CoreDNS deployment.
Current CoreDNS image mcr.microsoft.com/oss/kubernetes/coredns:v1.9.4-hotfix.20240704
I modify the deployment but it keeps getting written when restarting the deployment.
Thank you in advanced!
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Hi c2_confluent ,
Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.
Modifying CoreDNS in AKS requires creation of a ConfigMap with a specific name ‘coredns-custom’ in the kube-system namespace.
The configuration from this custom ConfigMap is read by CoreDNS and the associated Corefile is modified to incorporate the new settings.
To setup usage of Custom DNS Server as a resolver and since you are using the CoreDNS image mcr.microsoft.com/oss/kubernetes/coredns:v1.9.4-hotfix.20240704, which is a version higher than 1.6.x, you should be compatible with the 'forward' plugin. https://coredns.io/plugins/
To upgrade CoreDNS, you need to update the CoreDNS image in the deployment. You have mentioned that you have updated the the CoreDNS deployment YAML file. The following link gives you more detailed information: Customize CoreDNS for Azure Kubernetes Service (AKS) documentation
For basic troubleshooting of DNS resolution problems: https://learn.microsoft.com/en-us/troubleshoot/azure/azure-kubernetes/connectivity/basic-troubleshooting-dns-resolution-problems?source=recommendations
If you have any further queries, do let us know.
If the answer is helpful, please click "Accept Answer" and "Upvote it."
Hello, that is not a valid answer. The documentation to Customize CoreDNS for Azure Kubernetes Service (AKS) does not have instructions to update CoreDNS deployment.
I need to update coredns to 1.11. Which is the version that supports DNSTap to send to a remote endpoint over TLS.
The current version requires "skipverify" which changes the flag in code to not use SSL/TLS
Hi c2_confluent,
Thank you for reaching again and letting us know that the information provided was not helpful. Could you please provide more details. This will help me assist you better.
If you see a Pod Crashing, view the logs to see any errors, then adjust configs or rollback if necessary.
When upgrading a Kubernetes cluster, some care should be taken when upgrading the CoreDNS component to avoid backward incompatible configuration failures. At a high level, you'll want to review the CoreDNS release notes to see if the new version introduces backward incompatibilities or deprecations and adjust your Corefile as needed before upgrading CoreDNS.
You can check the CoreDNS logs to see if there are any errors or warnings related to the plugin,and update the Corefile accordingly.
I would like to give you the following articles that may fit into your case scenario: )
Hi c2_confluent,
Just checking in to see if you had a chance to see my response to your question. Please tell us if it was helpful and feel free to reach out to us if you have any queries.
If you feel that your queries have been resolved, please accept the answer by clicking the "Upvote" and "Accept Answer" on the post.
Hello. The documentation does not apply to this use case because event if I attempt to install coredns manually by patching, AKS still overwrites the changes immediately
Hello.
I have attempted to update using the patch command:
kubectl patch deployment coredns -n kube-system -p '{"spec":{"template":{"spec":{"containers":[{"name":"coredns","readinessProbe":{"httpGet":{"path":"/health","port":8080}}}]}}}}'
kubectl patch deployment coredns -n kube-system -p '{"spec":{"template":{"spec":{"containers":[{"name":"coredns", "image":"coredns/coredns:1.11.1"}]}}}}'
(this setting changes in AKS because the default is using path=/ready and port=8181)
Pod logs before it is terminated:
➜ ~ kubectl logs coredns-7fdf8445c4-cdq45 -n kube-system -f
[WARNING] No files matching import glob pattern: custom/*.server
[INFO] plugin/ready: Still waiting on: "kubernetes"
.:53
[WARNING] No files matching import glob pattern: custom/*.server
[INFO] plugin/reload: Running configuration SHA512 = 749525aefa8e363e150f0169e7afeef478d70907bd7600b40f6ff4c467926215d931bdf9d2d0dc4735a67d9bea84b8e1e29db3b186284592a82110ba726b22d0
CoreDNS-1.11.1
linux/amd64, go1.20.7, ae2bbc2
[WARNING] No files matching import glob pattern: custom/*.server
[WARNING] No files matching import glob pattern: custom/*.server
[WARNING] No files matching import glob pattern: custom/*.server
[INFO] SIGTERM: Shutting down servers then terminating
[INFO] plugin/health: Going into lameduck mode for 5
Hi c2_confluent,
Thank you for providing information. The issue needs deeper investigation.
We are working with our internal team and will get back to you soon.
Meanwhile,
Can you please let us know if you created image manually or getting it from aks cluster or from other sources while deploying. I have checked from my side, I didn't get the image version 1.11.1 from Docker hub.
Hi c2_confluent,
I have checked with our internal team, and they have replied saying AKS doesn’t support customizing CoreDNS version.
It is worth noting that some AKS customers do work around this by using the CoreDNS scaling feature to scale our CoreDNS replica count to 0, and then bring their own CoreDNS deployment with their own configuration. Granted to say that this is not a supported feature and not officially supported, and any modifications made to it may introduce potential risks.
Got it. Thank you for the update. Feel free to close this topic out.
Before I close this. Will there be any update on the CoreDNS version? 1.9.4 is pretty old (2022). Several updates have been made in past 2 years.
Also, can you get the exact commands they perform to adjust the Replica count and deploy their own version?
Hi c2_confluent,
Thank you for your patience and reaching to us back again.
We are working with our internal team and will get back to you soon.
Hi c2_confluent,
Thank you for your patience while we are reviewing your case.
For scaling down CoreDNS, read https://learn.microsoft.com/en-us/azure/aks/coredns-custom#configure-coredns-pod-scaling on how to leverage configmap to control coredns replica count according to node count.
For configuring a CoreDNS deployment, check the kubectl -n kube-system get svc -oyaml kube-dns and see the selector used is k8s-app: kube-dns.
This should be informative enough for a customer with sufficient Kubernetes knowledge to start.
Again, this is not recommended and not supported. IMO “exact commands” shouldn’t be something we deliver to customer.
About your question on Update on CoreDNS version: We plan to upgrade coredns to 1.11 for k8s 1.31.
If you have any further queries, do let us know.
If the answer is helpful, please click "Accept Answer" and "Upvote it."
Hi c2_confluent,
Just checking in to see if you had a chance to see my response to your question. Please tell us if it was helpful and feel free to reach out to us if you have any queries.
If you feel that your queries have been resolved, please accept the answer by clicking the "Upvote" and "Accept Answer" on the post.
Hi c2_confluent,
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