kube-apiserver位置、安装配置及PV自动创建故障排查求助

Hey there! Let's work through your questions step by step to get your Kubernetes setup sorted out.

The location depends on how you deployed Kubernetes:

• If you used kubeadm for deployment, the kube-apiserver binary is typically installed at /usr/bin/kube-apiserver on control plane nodes. However, it usually runs as a static Pod managed by kubelet, so you can find its manifest file at /etc/kubernetes/manifests/kube-apiserver.yaml.
• To locate the running kube-apiserver Pod, run this command:

  kubectl get pods -n kube-system | grep kube-apiserver
  

  You can access the Pod's shell to verify the binary path inside the container:

  kubectl exec -it <kube-apiserver-pod-name> -n kube-system -- /bin/sh
  # Inside the pod, check the path:
  which kube-apiserver
  

Why the command isn't found #

If you're using kubeadm, kube-apiserver runs as a static Pod, so you don't execute it directly on the host. Running kube-apiserver from the host shell will fail unless you've added the binary path to your PATH (or call it with the full /usr/bin/kube-apiserver path). But modifying the apiserver's configuration requires editing its static Pod manifest instead of running the command manually.

How to enable the DefaultStorageClass admission plugin #

1. Edit the kube-apiserver static Pod manifest:

   sudo vi /etc/kubernetes/manifests/kube-apiserver.yaml
   

2. Find the command section, look for the --enable-admission-plugins flag. If it exists, append DefaultStorageClass to the comma-separated list. If it doesn't exist, add the flag:

   command:
     - kube-apiserver
     - ... # other existing flags
     - --enable-admission-plugins=NodeRestriction,DefaultStorageClass
   

3. Save the file. Kubelet will automatically detect the change and restart the kube-apiserver Pod.

Setting a default StorageClass #

To make your example-nfs StorageClass the default (so PVCs without a storageClassName use it), run:

kubectl patch storageclass example-nfs -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

Looking at your PVC logs and StorageClass details, the core issue is that the external provisioner example.com/nfs isn't creating a PV for your PVC. Here's how to diagnose:

• First, confirm if the example.com/nfs provisioner is deployed and running:

  # Check for provisioner Pods (adjust namespace if you deployed it elsewhere)
  kubectl get pods -n kube-system | grep nfs-provisioner
  

  If no such Pod exists, you need to deploy the NFS external provisioner first. This usually involves deploying a Deployment/StatefulSet that runs the provisioner container, along with appropriate RBAC permissions to create PVs.
• If the provisioner Pod exists, check its logs for errors:

  kubectl logs -n kube-system <nfs-provisioner-pod-name>
  

  Common issues here include:
  • The provisioner can't reach your NFS server
  • Incorrect NFS server path or permissions
  • Missing RBAC permissions for the provisioner to create PVs
• Your PVC is explicitly using example-nfs as the StorageClass, so the DefaultStorageClass plugin won't affect this specific PVC—it only helps when no storageClassName is specified.

Here are key logs to inspect:

• PersistentVolume Controller logs: This controller manages PV/PVC binding and interacts with provisioners. It's part of the kube-controller-manager Pod:

  # First get the kube-controller-manager Pod name
  kubectl get pods -n kube-system | grep kube-controller-manager
  # Then filter logs for persistentvolume-controller
  kubectl logs -n kube-system <kube-controller-manager-pod-name> | grep persistentvolume-controller
  

• External provisioner logs: As mentioned earlier, check the logs of your example.com/nfs provisioner Pod to see why it's not creating PVs.
• PVC event history: You already ran kubectl describe pvc nfs, but rechecking events can show new updates. Use this command to watch events in real-time:

  kubectl events -w --field-selector involvedObject.name=nfs,involvedObject.kind=PersistentVolumeClaim
  

• StorageClass logs: While your StorageClass shows no events, you can still verify its configuration matches the provisioner's expected settings.

内容的提问来源于stack exchange，提问作者raj_arni