Kubernetes version 1.20.0 breaks the nfs-subdir-external-provisioner.
The PersistentVolumeClaim stays in status “Pending”:
$ k get pvc
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
test-claim Pending managed-nfs-storage 10hThe pod logs of client provisioner contains:
unexpected error getting claim reference: selfLink was empty, can’t make reference
$ kubectl logs nfs-client-provisioner
E0106 06:18:07.328905 1 controller.go:1004] provision "default/test-claim" class "managed-nfs-storage": unexpected error getting claim reference: selfLink was empty, can't make referenceunexpected error getting claim reference: selfLink was empty, can't make referenceThe deprecation of selfLinks in Kubernetes 1.20.0 is responsible for this.
As noted by nealman13 in his github comment setting the feature gate RemoveSelfLink to false is a workaround for this problem.
But Rancher K3S doesn’t come with a kube-apiserver.yaml file. But feature gates can be passed as commandline arguments directly to the service.
For a fresh install of K3S the following commandline can be used:
$ curl -sfL https://get.k3s.io | sh -s - --kube-apiserver-arg "feature-gates=RemoveSelfLink=false"An existing installation can be adjusted by changing the service directly:
$ nano /etc/systemd/system/k3s.service
...
ExecStart=/usr/local/bin/k3s \
server \
'--kube-apiserver-arg' \
'feature-gates=RemoveSelfLink=false' \
...