K
Q

How to mount folder with files in kubernetes

2/20/2020

I am running a docker image that has certain configuration files within it. I need to persist/mount the same folder to the disk as new files will get added later on. When I use standard volume mount in kubernetes, it mounts an empty directory without the intial configuration files. How do I make sure my initial files are copied to the volume while mounting?

        - mountPath: /tmp
          name: my-vol
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      schedulerName: default-scheduler
      securityContext: {}
      terminationGracePeriodSeconds: 30
      volumes:
      - name: my-vol
        persistentVolumeClaim:
          claimName: wso2-disk2```
-- Pranav
docker
docker-volume
kubernetes

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2 Answers

2/20/2020

A possible solution could be the use the node storage mounted on containers (easiest way) or using a DFS solution like NFS, GlusterFS, and so on.

Another and recommended way to achieve what you need is to use a persistent volumes to share the same files between your containers.

Assuming you have a kubernetes cluster that has only one Node, and you want to share the path /mtn/data of your node with your pods (Source):

Create a PersistentVolume:

A hostPath PersistentVolume uses a file or directory on the Node to emulate network-attached storage.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: task-pv-volume
  labels:
    type: local
spec:
  storageClassName: manual
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  hostPath:
    path: "/mnt/data"

Create a PersistentVolumeClaim:

Pods use PersistentVolumeClaims to request physical storage

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: task-pv-claim
spec:
  storageClassName: manual
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 3Gi

Look at the PersistentVolumeClaim:

kubectl get pvc task-pv-claim

The output shows that the PersistentVolumeClaim is bound to your PersistentVolume, task-pv-volume.

NAME            STATUS    VOLUME           CAPACITY   ACCESSMODES   STORAGECLASS   AGE
task-pv-claim   Bound     task-pv-volume   10Gi       RWO           manual         30s

Create a deployment with 2 replicas for example:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      volumes:
        - name: task-pv-storage
          persistentVolumeClaim:
            claimName: task-pv-claim
      containers:
        - name: task-pv-container
          image: nginx
          ports:
            - containerPort: 80
              name: "http-server"
          volumeMounts:
            - mountPath: "/mnt/data"
              name: task-pv-storage

Now you can check inside both container the path /mnt/data has the same files.

If you have cluster with more than 1 node I recommend you to think about the other types of persistent volumes or using DFS.

References: Configure persistent volumes Persistent volumes Volume Types

-- mWatney
Source: StackOverflow
2/20/2020

The suggested way to provide configurations to your pod is by creating a configmap for your configurations and mount it in your pod using volumes. This guide ( https://kubernetes.io/docs/concepts/storage/volumes/#configmap) descibes how to do that.

Other ways are to create a persistent volume and persistent volume claim in your cluster and copy your configuration file in that path. Mount the persistent volume in your pod.

You can also copy your configuration on one of the nodes in your cluster and mount that path using hostPath but this requires that your pod should also run on the same node as it tries to look for the path in that node. (Not a recommended approach)

-- anmol agrawal
Source: StackOverflow