Kubernetes Certification Exam Self-Study Series | hostPath

Book source: "CKA/CKAD Test Guide: From Docker to Kubernetes Complete Raiders"

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Using the storage method of hostPath is similar to the command docker run -v /data:/xx when creating a docker container, which means that the directory /data in the physical machine is mapped to the /xx directory of the container. If the pod is deleted , the data is still retained.

Step 1: Create a pod yaml file host.yaml with the following content.

[root@vms10 volume]# cat host.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: demo
  labels:
    purpose: demonstrate-envars 
spec:
  volumes:
  - name: volume1
    hostPath:
      path: /data 
  containers:
  - name: demo1
    image: busybox 
    imagePullPolicy: IfNotPresent 
    command: ['sh', '-c', 'sleep 5000']
    volumeMounts: 
    - mountPath: /xx 
      name: volume1
 
![image.png](https://p9-juejin.byteimg.com/tos-cn-i-k3u1fbpfcp/bfb4165679264e149a846eeab8cb63b8~tplv-k3u1fbpfcp-watermark.image?)
  - name: demo2
    image: busybox 
    imagePullPolicy: IfNotPresent 
    command: ['sh', '-c', 'sleep 5000']
    volumeMounts:
    - mountPath: /xx 
      name: volume1
[root@vms10 volume]#

In this yaml file, a volume named volume1 is created under the volumes field, and the type is hostPath, which corresponds to the directory /data of the physical machine (specified by path).

Two containers are defined, and volumeMounts is used in each container to mount the volume volume1 to the /xx directory of the container (specified by mount Path), so the directory /xx in each container is mounted to the /data directory of the physical machine .

Step 2: Create and view pods.

[root@vms10 volume]# kubectl apply -f host.yaml 
pod/demo created
[root@vms10 volume]# kubectl get pods
NAME   READY   STATUS  RESTARTS  AGE 
demo   2/2    Running   0        11s 
[root@vms10 volume]#

Step 3: Check the properties of the pod to confirm that HostPath is being used now.

[root@vms10 volume]# kubectl describe pod demo | grep -A3 Volumes 
Volumes:
  volume1:
    Type:     HostPath (bare host directory volume)
    Path:     /data 
[root@vms10 volume]#

As can be seen from the above, /xx in the pod mounts the /data directory of the physical machine.

Step 4: Check the machine where the pod is located.

[root@vms10 volume]# kubectl get pods -o wide 
NAME   READY   STATUS    RESTARTS     AGE     IP             NODE 
demo   2/2     Running   0            3m14s   10.244.3.31    vms12.rhce.cc 
[root@vms10 volume]#

You can see that the pod is running on vms12.

Step 5: Copy a file on the master to the /xx directory of the demo1 container in this pod.

[root@vms10 volume]# kubectl cp /etc/hosts demo:/xx -c demo1
[root@vms10 volume]#

Step 6: Switch to vms12 and check whether the file is placed in the /data directory of vms12.

[root@vms12 ~]#
[root@vms12 ~]# ls /data/
hosts
[root@vms12 ~]#

Step 7: Delete this pod.