Create 9.upgrade-nebula-cluster.md (#1190)

* Create 9.upgrade-nebula-cluster.md

* Update 9.upgrade-nebula-cluster.md

* Update 9.upgrade-nebula-cluster.md

* Update 9.upgrade-nebula-cluster.md

docs-2.0/nebula-operator/9.upgrade-nebula-cluster.md

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+# 升级Nebula Graph集群
+
+本文介绍如何升级通过Nebula Operator创建的Nebula Graph集群。
+
+## 前提条件
+
+已创建Nebula Graph集群。具体步骤，参见[使用Kubectl创建Nebula Graph集群](3.deploy-nebula-graph-cluster/3.1create-cluster-with-kubectl.md)。
+
+本文示例中待升级的Nebula Graph版本为2.5.1，其YAML文件名为`apps_v1alpha1_nebulacluster.yaml`。
+
+## 使用限制
+
+- 只支持使用Nebula Operator创建的Nebula Graph集群。
+
+- 只支持升级Nebula Graph 2.5.x至2.6.x版本。
+
+## 操作步骤
+
+1. 查看集群中服务的镜像版本。
+
+  ```bash
+  kubectl get pods -l app.kubernetes.io/cluster=nebula  -o jsonpath="{.items[*].spec.containers[*].image}" |tr -s '[[:space:]]' '\n' |sort |uniq -c
+  ```
+
+  返回：
+
+  ```bash
+        1 vesoft/nebula-graphd:v2.5.1
+        1 vesoft/nebula-metad:v2.5.1
+        3 vesoft/nebula-storaged:v2.5.1  
+  ```
+
+2. 编辑`apps_v1alpha1_nebulacluster.yaml`并将所有`version`的值从v2.5.1修改至{{nebula.branch}}。
+
+  修改后的YAML文件内容如下：
+
+  ```yaml
+  apiVersion: apps.nebula-graph.io/v1alpha1
+  kind: NebulaCluster
+  metadata:
+      name: nebula
+  spec:
+      graphd:
+          resources:
+              requests:
+                  cpu: "500m"
+                  memory: "500Mi"
+              limits:
+                  cpu: "1"
+                  memory: "1Gi"
+          replicas: 2
+          image: vesoft/nebula-graphd
+          version: {{nebula.branch}} //将值从v2.5.1修改至{{nebula.branch}}。
+          service:
+              type: NodePort
+              externalTrafficPolicy: Local
+          storageClaim:
+              resources:
+                  requests:
+                      storage: 2Gi
+              storageClassName: local-path
+      metad:
+          resources:
+              requests:
+                  cpu: "500m"
+                  memory: "500Mi"
+              limits:
+                  cpu: "1"
+                  memory: "1Gi"
+          replicas: 1
+          image: vesoft/nebula-metad
+          version: {{nebula.branch}} //将值从v2.5.1修改至{{nebula.branch}}。
+          storageClaim:
+              resources:
+                  requests:
+                      storage: 2Gi
+              storageClassName: local-path
+      storaged:
+          resources:
+              requests:
+                  cpu: "500m"
+                  memory: "500Mi"
+              limits:
+                  cpu: "1"
+                  memory: "1Gi"
+          replicas: 3
+          image: vesoft/nebula-storaged
+          version: {{nebula.branch}} //将值从v2.5.1修改至{{nebula.branch}}。
+          storageClaim:
+              resources:
+                  requests:
+                      storage: 2Gi
+              storageClassName: local-path
+      reference:
+          name: statefulsets.apps
+          version: v1
+      schedulerName: default-scheduler
+      imagePullPolicy: IfNotPresent
+  ```
+
+3. 执行以下命令将版本升级的更新应用于集群CR中。
+
+  ```bash
+  kubectl apply -f apps_v1alpha1_nebulacluster.yaml
+  ```
+
+4. 等待约2分钟后，执行以下命令可查看到服务的镜像版本变更为{{nebula.branch}}。
+
+  ```bash
+  kubectl get pods -l app.kubernetes.io/cluster=nebula  -o jsonpath="{.items[*].spec.containers[*].image}" |tr -s '[[:space:]]' '\n' |sort |uniq -c
+  ```
+
+  返回：
+
+  ```bash
+        1 vesoft/nebula-graphd:{{nebula.branch}}
+        1 vesoft/nebula-metad:{{nebula.branch}}
+        3 vesoft/nebula-storaged:{{nebula.branch}}  
+  ```