Issues with Raspberry Pi

Here, we describe issues with using Raspberry Pi together with the testbed

"Multus" issue when adding RPi as worker node (fixed)

Problem: Multus pod couldn’t see any CNI plugins because nothing was mounted at /opt/cni/bin, and its CNI_PATH variable was unset.

Solution: Mounted the host’s /opt/cni/bin directory into the Multus container and set CNI_PATH=/opt/cni/bin via a DaemonSet patch. Once Multus could execute /opt/cni/bin/calico and calico-ipam, the kubelet could create the network sandbox, so Zun/Kubernetes pods on the Raspberry Pi worker started normally.

Below is the exact sequence we ran—copy-ready commands and the reason for each— that made Multus see the Calico CNI plugins and let containers start on the Raspberry Pi (ARM) worker. Note: "worker-21" is the worker for our case.

1. Spot the error

kubectl describe pod <pending-pod>

Result: failed to find plugin "calico" in path [/opt/cni/bin]

1. Verify CNI binaries exist on the node

ssh worker-21 ls -l /opt/cni/bin | grep calico

Result: CNI binaries exist

1. Find the Multus pod on that node

MULTUS=$(kubectl -n kube-system get pod -l app=multus -o wide \ --field-selector spec.nodeName=worker-21 -o jsonpath='{.items[0].metadata.name}')

Result: Captured pod name (kube-multus-ds-xxxx).

1. Look inside the Multus container

kubectl -n kube-system exec "$MULTUS" -- sh -c 'echo CNI_PATH=$CNI_PATH; ls /opt/cni/bin 2>&1'

Result: CNI_PATH= (unset) and ls: /opt/cni/bin: No such file or directory → Multus had no mount and no env var.

1. Patch the DaemonSet to add mount & env

kubectl -n kube-system patch daemonset kube-multus-ds --type=json -p '[
  {
    "op": "add",
    "path": "/spec/template/spec/containers/0/volumeMounts/-",
    "value": {
      "name": "cnibin",
      "mountPath": "/opt/cni/bin",
      "readOnly": true
    }
  }
]'

kubectl -n kube-system patch daemonset kube-multus-ds --type=json -p '[
  {
    "op": "add",
    "path": "/spec/template/spec/volumes/-",
    "value": {
      "name": "cnibin",
      "hostPath": {
        "path": "/opt/cni/bin",
        "type": "DirectoryOrCreate"
      }
    }
  }
]'

Result: Env: tells Multus where to look. VolumeMount + Volume: exposes host /opt/cni/bin inside the pod (read-only).

1. Watch rollout

kubectl -n kube-system rollout status ds kube-multus-ds

Result: Waited until new Multus pods were Running.

1. Re-check inside new Multus pod

MULTUS=$(kubectl -n kube-system get pod -l app=multus \
  --field-selector spec.nodeName=worker-21 \
  -o jsonpath='{.items[0].metadata.name}')
kubectl -n kube-system exec "$MULTUS" -- ls -1 /opt/cni/bin | head

Result: You should see the Calico (and related) CNI plugin binaries listed, for example:

calico
calico-ipam
bandwidth
portmap
...

1. Watch the previously stuck container

kubectl -n <project-ns> get pod <zun-pod> -w

Result: Phase changed ContainerCreating → Running within ~1 minute.