Updating the CoreDNS self-managed add-on - Amazon EKS

Updating the CoreDNS self-managed add-on

Important

This topic will be removed from this guide on July 1, 2023. We recommend adding the Amazon EKS type of the add-on to your cluster instead of using the self-managed type of the add-on. If you're not familiar with the difference between the types, see Amazon EKS add-ons. For more information about adding an Amazon EKS add-on, to your cluster, see Creating an add-on.

CoreDNS is a flexible, extensible DNS server that can serve as the Kubernetes cluster DNS. When you launch an Amazon EKS cluster with at least one node, two replicas of the CoreDNS image are deployed by default, regardless of the number of nodes deployed in your cluster. The CoreDNS pods provide name resolution for all pods in the cluster. The CoreDNS pods can be deployed to Fargate nodes if your cluster includes an AWS Fargate profile with a namespace that matches the namespace for the CoreDNS deployment. For more information about CoreDNS, see Using CoreDNS for Service Discovery in the Kubernetes documentation.

Prerequisites

  • An existing Amazon EKS cluster. To deploy one, see Getting started with Amazon EKS.

  • If your cluster is 1.21 or later, make sure that your Amazon VPC CNI plugin for Kubernetes and CoreDNS add-ons are at the minimum versions listed in Cluster add-ons.

To update the CoreDNS self-managed add-on

  1. Confirm that you have the self-managed type of the add-on installed on your cluster. Replace my-cluster with the name of your cluster.

    aws eks describe-addon --cluster-name my-cluster --addon-name coredns --query addon.addonVersion --output text

    If an error message is returned, you have the self-managed type of the add-on installed on your cluster. The remaining steps in this topic are for updating the self-managed type of the add-on. If a version number is returned, you have the Amazon EKS type of the add-on installed on your cluster. To update it, use the procedure in Updating an add-on, rather than using the procedure in this topic. If you're not familiar with the differences between the add-on types, see Amazon EKS add-ons.

  2. See which version of the container image is currently installed on your cluster.

    kubectl describe deployment coredns -n kube-system | grep Image | cut -d ":" -f 3

    The example output is as follows.

    v1.8.7-eksbuild.2

    The following table lists the latest version of the CoreDNS container image available for each Amazon EKS cluster version.

    Latest available CoreDNS container image version for each Amazon EKS cluster version
    Kubernetes version 1.24 1.23 1.22 1.21 1.20 1.19
    v1.8.7-eksbuild.3 v1.8.7-eksbuild.3 v1.8.7-eksbuild.1 v1.8.4-eksbuild.2 v1.8.3-eksbuild.1 1.8.0
    Important

    The container image versions listed in this table might not match the versions of the Amazon EKS type of this add-on. This is because Amazon EKS add-on versions don't always match container image versions. When you update an Amazon EKS add-on, you specify a valid Amazon EKS add-on version. When you update a self-managed add-on, you specify a valid container image version.

  3. If your current CoreDNS version is v1.5.0 or later, but earlier than the version listed in the CoreDNS versions table, then skip this step. If your current version is earlier than 1.5.0, then you need to modify the ConfigMap for CoreDNS to use the forward add-on, rather than the proxy add-on.

    1. Open the configmap with the following command.

      kubectl edit configmap coredns -n kube-system

    2. Replace proxy in the following line with forward. Save the file and exit the editor.

      proxy . /etc/resolv.conf

  4. If you originally deployed your cluster on Kubernetes 1.17 or earlier, then you may need to remove a discontinued line from your CoreDNS manifest.

    Important

    You must complete this step before updating to CoreDNS version 1.7.0, but it's recommended that you complete this step even if you're updating to an earlier version.

    1. Check to see if your CoreDNS manifest has the line.

      kubectl get configmap coredns -n kube-system -o jsonpath='{$.data.Corefile}' | grep upstream

      If no output is returned, your manifest doesn't have the line and you can skip to the next step to update CoreDNS. If output is returned, then you need to remove the line.

    2. Edit the ConfigMap with the following command, removing the line in the file that has the word upstream in it. Do not change anything else in the file. Once the line is removed, save the changes.

      kubectl edit configmap coredns -n kube-system -o yaml

  5. Retrieve your current CoreDNS image version:

    kubectl describe deployment coredns -n kube-system | grep Image

    The example output is as follows.

    602401143452.dkr.ecr.region-code.amazonaws.com/eks/coredns:v1.8.7-eksbuild.2

  6. If you're updating to CoreDNS 1.8.3 or later, then you need to add the endpointslices permission to the system:coredns Kubernetes clusterrole.

    kubectl edit clusterrole system:coredns -n kube-system

    Add the following lines under the existing permissions lines in the rules section of the file.

    ...
- apiGroups:
  - discovery.k8s.io
  resources:
  - endpointslices
  verbs:
  - list
  - watch
...

  7. Update the CoreDNS add-on by replacing 602401143452 and region-code with the values from the output returned in a previous step. Replace 1.8.7-eksbuild.3 with the version that you want to update to.

    kubectl set image deployment.apps/coredns -n kube-system  coredns=602401143452.dkr.ecr.region-code.amazonaws.com/eks/coredns:v1.8.7-eksbuild.3

    The example output is as follows.

    deployment.apps/coredns image updated

  8. Check the container image version again to confirm that it was updated to the version that you specified in the previous step.

    kubectl describe deployment coredns -n kube-system | grep Image | cut -d ":" -f 3

    The example output is as follows.

    v1.8.7-eksbuild.3