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為 Kubernetes 部署 NFS StorageClass

使用 NFS provisioner 為私有 Kubernetes 叢集提供持久化儲存。

peterlee
peterlee
Aug 27, 2019
English繁中
為 Kubernetes 部署 NFS StorageClass

這份 2019 年的 lab 筆記使用 NFS-backed StorageClass 與舊版 nfs-client-provisioner，下方保留當時的 extensions/v1beta1 Deployment。新建叢集請使用 NFS subdirectory external provisioner 的安裝方式。

在前一篇 kubeadm cluster 裡，Pods 可能被重新建立到不同節點。我用 NFS 提供共享的持久化儲存，讓 provisioner 依 PVC 建立對應目錄。

在 CentOS 安裝 NFS server

Server 位於同一個 LAN，位址為 192.168.2.104。安裝 nfs-utils、建立 /opt/nfs，再設定 /etc/exports：

$ yum install nfs-utils

# share /opt/nfs to 192.168.2.1/24 with read/write access.
# modify mount point
# /etc/exports
/opt/nfs 192.168.2.1/24(rw,sync,no_root_squash,no_all_squash)

$ sudo systemctl restart nfs-server
$ sudo systemctl enable nfs-server

確認匯出路徑：

$ showmount -e 192.168.2.104
Export list for 192.168.2.104:
/opt/nfs 192.168.2.1/24

這會將 NFS 開放給設定的內部網段。實際授權應限制在需要的 nodes，並評估 no_root_squash 所保留的 client root 權限。

定義 provisioner 與 StorageClass

將以下內容存成 nfs-storage.yml。Deployment 使用 ServiceAccount 存取 Kubernetes，並將 NFS 目錄掛載至 /persistentvolumes：

# nfs-storage.yml
apiVersion: v1
kind: ServiceAccount
metadata:
  name: nfs-client-provisioner

---
kind: Deployment
apiVersion: extensions/v1beta1
metadata:
  name: nfs-storage
spec:
  replicas: 1
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: nfs-client-provisioner
    spec:
      serviceAccountName: nfs-client-provisioner
      containers:
        - name: nfs-client-provisioner
          image: quay.io/external_storage/nfs-client-provisioner:latest
          volumeMounts:
            - name: nfs-client-root
              mountPath: /persistentvolumes
          env:
            - name: PROVISIONER_NAME
              value: nfs-storage
            - name: NFS_SERVER
              value: 192.168.2.104
            - name: NFS_PATH
              value: /opt/nfs
      volumes:
        - name: nfs-client-root
          nfs:
            server: 192.168.2.104
            path: /opt/nfs
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: managed-nfs-storage
provisioner: nfs-storage
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: default
provisioner: nfs-storage

PROVISIONER_NAME 必須與 StorageClass 的 provisioner 相同，NFS_SERVER 與 NFS_PATH 則需對應 server 設定。

加入 RBAC

將以下內容存成 nfs-rbac.yaml，授予 provisioner 管理 PV、PVC events 與 leader lock 所需的權限：

# nfs-rbac.yaml
kind: ClusterRole
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: nfs-client-provisioner-runner
rules:
  - apiGroups: [""]
    resources: ["persistentvolumes"]
    verbs: ["get", "list", "watch", "create", "delete"]
  - apiGroups: [""]
    resources: ["persistentvolumeclaims"]
    verbs: ["get", "list", "watch", "update"]
  - apiGroups: ["storage.k8s.io"]
    resources: ["storageclasses"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "update", "patch"]
---
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: run-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    namespace: default
roleRef:
  kind: ClusterRole
  name: nfs-client-provisioner-runner
  apiGroup: rbac.authorization.k8s.io
---
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
rules:
  - apiGroups: [""]
    resources: ["endpoints"]
    verbs: ["get", "list", "watch", "create", "update", "patch"]
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: leader-locking-nfs-client-provisioner
subjects:
  - kind: ServiceAccount
    name: nfs-client-provisioner
    # replace with namespace where provisioner is deployed
    namespace: default
roleRef:
  kind: Role
  name: leader-locking-nfs-client-provisioner
  apiGroup: rbac.authorization.k8s.io

RoleBinding 與 ClusterRoleBinding 內的 ServiceAccount namespace 必須和 Deployment 一致；此例使用 default。套用兩個檔案：

kubectl apply -f nfs-rbac.yaml
kubectl apply -f nfs-storage.yml

選擇預設 StorageClass

需要讓未指定 StorageClass 的新 PVC 使用 NFS 時，將選定的 class 標為 default：

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

完整規則見 Kubernetes 預設 StorageClass 文件。建立測試 PVC 後，確認它轉為 Bound、對應 PV 已建立，且 NFS 目錄出現預期的儲存路徑。

#kubernetes#cloud