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bootstrapping flannel

参考文献

手順

  1. vxlan moduleをインストールする 

    sudo apt install -y linux-modules-extra-raspi locate
sudo updatedb
sudo modprobe vxlan
sudo lsmod | grep vxlan

  2. flannel k8s manifestsを公式から取得する

  3. masterブランチから取得していますが2021/03/06 時点では release tag v0.13.1-rc2 の内容

    sudo mkdir -p /etc/kubernetes/manifests
sudo curl -o /etc/kubernetes/manifests/kube-flannel.yml -sSL https://raw.githubusercontent.com/flannel-io/flannel/master/Documentation/kube-flannel.yml

  4. manifestsを修正する

    • net-conf.json の Network をcontroller-managerの--cluster-cidrで指定した値に変更する
    • etcdに用いたcertificateやadminのkubeconfigをkube-flannelコンテナへbind mountする
            volumeMounts:
        - name: var-lib-kubernetes-dir
          mountPath: /var/lib/kubernetes/

      volumes:
      - name: var-lib-kubernetes-dir
        hostPath:
          path: /var/lib/kubernetes
    • /opt/bin/flanneld の起動オプション
      • --kubeconfig-file
      • --etcd-endpoints
      • --etcd-prefix
      • --etcd-keyfile
      • --etcd-certfile
      • --etcd-cafile

      • --v

        sudo vim /etc/kubernetes/manifests/kube-flannel.yml
        修正後の/etc/kubernetes/manifests/kube-flannel.yml 
        ---
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: psp.flannel.unprivileged
  annotations:
    seccomp.security.alpha.kubernetes.io/allowedProfileNames: docker/default
    seccomp.security.alpha.kubernetes.io/defaultProfileName: docker/default
    apparmor.security.beta.kubernetes.io/allowedProfileNames: runtime/default
    apparmor.security.beta.kubernetes.io/defaultProfileName: runtime/default
spec:
  privileged: false
  volumes:
  - configMap
  - secret
  - emptyDir
  - hostPath
  allowedHostPaths:
  - pathPrefix: "/etc/cni/net.d"
  - pathPrefix: "/etc/kube-flannel"
  - pathPrefix: "/run/flannel"
  readOnlyRootFilesystem: false
  # Users and groups
  runAsUser:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  # Privilege Escalation
  allowPrivilegeEscalation: false
  defaultAllowPrivilegeEscalation: false
  # Capabilities
  allowedCapabilities: ['NET_ADMIN', 'NET_RAW']
  defaultAddCapabilities: []
  required
  seLinux:
    # SELinux is unused in CaaSP
    rule: 'RunAsAny'
---
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: flannel
rules:
- apiGroups: ['extensions']
  resources: ['podsecuritypolicies']
  verbs: ['use']
  resourceNames: ['psp.flannel.unprivileged']
- apiGroups:
  - ""
  resources:
  - pods
  verbs:
  - get
- apiGroups:
  - ""
  resources:
  - nodes
  verbs:
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - nodes/status
  verbs:
  - patch
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: flannel
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: flannel
subjects:
- kind: ServiceAccount
  name: flannel
  namespace: kube-system
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: flannel
  namespace: kube-system
---
kind: ConfigMap
apiVersion: v1
metadata:
  name: kube-flannel-cfg
  namespace: kube-system
  labels:
    tier: node
    app: flannel
data:
  cni-conf.json: |
    {
      "name": "cbr0",
      "cniVersion": "0.3.1",
      "plugins": [
        {
          "type": "flannel",
          "delegate": {
            "hairpinMode": true,
            "isDefaultGateway": true
          }
        },
        {
          "type": "portmap",
          "capabilities": {
            "portMappings": true
          }
        }
      ]
    }
  net-conf.json: |
    {
      "Network": "10.200.0.0/16",
      "Backend": {
        "Type": "vxlan"
      }
    }
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: kube-flannel-ds
  namespace: kube-system
  labels:
    tier: node
    app: flannel
spec:
  selector:
    matchLabels:
      app: flannel
  template:
    metadata:
      labels:
        tier: node
        app: flannel
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/os
                operator: In
                values:
                - linux
      hostNetwork: true
      priorityClassName: system-node-critical
      tolerations:
      - operator: Exists
        effect: NoSchedule
      serviceAccountName: flannel
      initContainers:
      - name: install-cni-plugin
       #image: flannelcni/flannel-cni-plugin:v1.0.1 for ppc64le and mips64le (dockerhub limitations may apply)
        image: rancher/mirrored-flannelcni-flannel-cni-plugin:v1.0.1
        command:
        - cp
        args:
        - -f
        - /flannel
        - /opt/cni/bin/flannel
        volumeMounts:
        - name: cni-plugin
          mountPath: /opt/cni/bin
      - name: install-cni
       #image: flannelcni/flannel:v0.16.3 for ppc64le and mips64le (dockerhub limitations may apply)
        image: rancher/mirrored-flannelcni-flannel:v0.16.3
        command:
        - cp
        args:
        - -f
        - /etc/kube-flannel/cni-conf.json
        - /etc/cni/net.d/10-flannel.conflist
        volumeMounts:
        - name: cni
          mountPath: /etc/cni/net.d
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
      containers:
      - name: kube-flannel
       #image: flannelcni/flannel:v0.16.3 for ppc64le and mips64le (dockerhub limitations may apply)
        image: rancher/mirrored-flannelcni-flannel:v0.16.3
        command:
        - /opt/bin/flanneld
        args:
        - --ip-masq
        - --kube-subnet-mgr
        - --kubeconfig-file=/var/lib/kubernetes/admin.kubeconfig
        - --etcd-endpoints=https://k8s-master:4001
        - --etcd-prefix=/coreos.com/network
        - --etcd-keyfile=/var/lib/kubernetes/kubernetes-key.pem
        - --etcd-certfile=/var/lib/kubernetes/kubernetes.pem
        - --etcd-cafile=/var/lib/kubernetes/ca.pem
        - --v=10
        resources:
          requests:
            cpu: "100m"
            memory: "50Mi"
          limits:
            cpu: "100m"
            memory: "50Mi"
        securityContext:
          privileged: false
          capabilities:
            add: ["NET_ADMIN", "NET_RAW"]
        env:
        - name: POD_NAME
          valueFrom:
            fieldRef:
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        volumeMounts:
        - name: run
          mountPath: /run/flannel
        - name: flannel-cfg
          mountPath: /etc/kube-flannel/
        - name: xtables-lock
          mountPath: /run/xtables.lock
        - name: var-lib-kubernetes-dir
          mountPath: /var/lib/kubernetes/
      volumes:
      - name: run
        hostPath:
          path: /run/flannel
      - name: cni-plugin
        hostPath:
          path: /opt/cni/bin
      - name: cni
        hostPath:
          path: /etc/cni/net.d
      - name: flannel-cfg
        configMap:
          name: kube-flannel-cfg
      - name: xtables-lock
        hostPath:
          path: /run/xtables.lock
          type: FileOrCreate
      - name: var-lib-kubernetes-dir
        hostPath:
          path: /var/lib/kubernetes

  5. flannel Podをデプロイ

kubectl apply -f /etc/kubernetes/manifests/kube-flannel.yml

エラー事例

  1. flannelが参照するkubeconfigが正しくない

    • flannel-io/flannel Documentation/kube-flannel.yml そのままだと発生した 
      Neither --kubeconfig nor --master was specified.  Using the inClusterConfig.  This might not work.
error creating inClusterConfig, falling back to default config: open /var/run/secrets/kubernetes.io/serviceaccount/token: no such file or directory
Failed to create SubnetManager: fail to create kubernetes config: invalid configuration: no configuration has been provided, try setting KUBERNETES_MASTER environment variable

  2. Failed to create SubnetManager: fail to create kubernetes config: stat "/var/lib/kubernetes/admin.kubeconfig": no such file or directory

    • --kubeconfig-file オプションで指定したkubeconfig pathが正しくない
      • 私のケースでは --kubeconfig-file="/var/lib/kubernetes/admin.kubeconfig" としているとダブルクォート(") がパスに含まれてしまっていることに気付くのに時間かかりました(正しくは --kubeconfig-file=/var/lib/kubernetes/admin.kubeconfig)

  3. Error registering network: failed to acquire lease: node "k8s-node1" pod cidr not assigned

    • Nodeリソースの .spec.podCIDR が登録されていない
    • 確認方法 
      kubectl get nodes -o jsonpath='{.items[*].spec.podCIDR}'

    • kube-controller-manager の設定不備の可能性

    • (kube-controller-manager が正しい場合) Nodeリソースの .spec.podCIDR を手動設定して回避する 

      kubectl patch node <NODE_NAME> -p '{"spec":{"podCIDR":"<SUBNET>"}}'

  4. Error registering network: failed to configure interface flannel.1: failed to ensure address of interface flannel.1: link has incompatible addresses. Remove additional addresses and try again.