mysql - 由NFS动态预配器支持时，mysql容器不会在kubernetes上启动

Question

我在使mysql容器正确启动方面遇到问题。但总而言之，即使NFS安装在容器中，并且使用nfs动态预配器，mysql容器也不会启动并抛出mkdir: cannot create directory '/var/lib/mysql/': File exists错误，并且看起来工作正常。

我从https://github.com/kubernetes-incubator/external-storage/tree/master/nfs-client在我的K8群集上安装了Dyanamic NFS设置程序。它们在说明上显示的测试声明和测试 Pane 。

现在运行mysql，我从这里获取代码片段:

https://kubernetes.io/docs/tasks/run-application/run-single-instance-stateful-application/
kubectl apply mysql-pvc.yaml

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  storageClassName: managed-nfs-storage  <--- THIS MATCHES MY NFS STORAGECLASS
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi

kubectl apply -f mysql-deployment.yaml

apiVersion: v1
kind: Service
metadata:
  name: mysql
spec:
  ports:
  - port: 3306
  selector:
    app: mysql
  clusterIP: None
---
apiVersion: apps/v1 # for versions before 1.9.0 use apps/v1beta2
kind: Deployment
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
      - image: mysql:5.6
        name: mysql
        env:
          # Use secret in real usage
        - name: MYSQL_ROOT_PASSWORD
          value: password
        ports:
        - containerPort: 3306
          name: mysql
        volumeMounts:
        - name: mysql-persistent-storage
          mountPath: /var/lib/mysql
      volumes:
      - name: mysql-persistent-storage
        persistentVolumeClaim:
          claimName: mysql-pv-claim

kubectl get pv,pvc
NAME                                                        CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                          STORAGECLASS          REASON   AGE
persistentvolume/mysql-pv-volume                            20Gi       RWO            Retain           Bound    default/mysql-pv-claim         managed-nfs-storage            5m16s

NAMESPACE      NAME                                    STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS          AGE
default        persistentvolumeclaim/mysql-pv-claim    Bound    mysql-pv-volume                            20Gi       RWO            managed-nfs-storage   5m27s

pv由动态预配器自动创建

得到错误...

$ kubectl logs mysql-7d7fdd478f-l2m8h
2020-03-05 18:26:21+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.6.47-1debian9 started.
2020-03-05 18:26:21+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
2020-03-05 18:26:21+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 5.6.47-1debian9 started.
mkdir: cannot create directory '/var/lib/mysql/': File exists

此错误使容器无法启动...

我去删除了部署，并添加了 command: [ "/bin/sh", "-c", "sleep 100000" ]，这样容器就会启动...

进入容器后，我检查了NFS支架是否正确安装并且可写...

# df -h | grep mysql
nfs1.example.com:/k8/default-mysql-pv-claim-pvc-0808d1bd-69ca-4ff5-825a-b846b1133e3a  1.0T  1.6G 1023G   1% /var/lib/mysql

如果我创建一个“本地” PV

apiVersion: v1
kind: PersistentVolume
metadata:
  name: mysql-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 20Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"

并创建了mysql部署后，mysql pod可以正常启动。

因此，在这一点上，使用动态配置(可能仅在NFS上进行配置)，mysql容器不起作用。

有人有什么建议吗？

Answer 1

我不确定这是什么原因，所以这里有几个选择。

首先，您可以尝试设置 securityContext ，因为在没有适当权限的情况下可能会挂载卷。

apiVersion: v1
kind: Pod
metadata:
  name: security-context-demo
spec:
  securityContext:
    runAsUser: 1000
    runAsGroup: 3000
    fsGroup: 2000
  volumes:
  - name: sec-ctx-vol
    emptyDir: {}
  containers:
  - name: sec-ctx-demo
    image: busybox
    command: [ "sh", "-c", "sleep 1h" ]
    volumeMounts:
    - name: sec-ctx-vol
      mountPath: /data/demo
    securityContext:
      allowPrivilegeEscalation: false

您可以通过在容器内键入 id和 gid来找到正确的组ID和用户。
或者只是使用 kubectl exec -it <pod-name> bash。

其次，尝试使用 subPath

volumeMounts:
- name: mysql-persistent-storage
  mountPath: "/var/lib/mysql"
  subPath: mysql

如果那行不通，我将使用创建目录的 initContainer在另一个Pod上测试NFS。
我可能会使用 this guide重做整个nfs。