<p>I have 2 containers in a pod.
1. Webapp
2. Nginx
I would like to share the data from Webapp container /var/www/webapp/ with the nginx container. /var/www/html</p>

<pre><code>/var/www/webapp ( folder structure )
│   index.php
│       
│
└───folder1
│   │   service1.php
│   │   
│   └───subfolder1
│       │   app.php
│   
└───folder2
    │   service2.php  
</code></pre>

<p>The folder is mounted properly but all the files are missing.</p>

<pre><code>apiVersion: apps/v1
kind: Deployment
    spec:
      volumes:
      - name: webapp-data
        persistentVolumeClaim:
          claimName: webapp-data
      containers:
      - name: webapp
        image: webapp
        imagePullPolicy: Always 
        volumeMounts:
        - name: webapp-data
          mountPath: /var/www/webapp/
       - name: nginx
        imagePullPolicy: Always
        image: nginx
        volumeMounts:
        - name: webapp-data
          mountPath: /var/www/html/
</code></pre>

<pre><code>apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: webapp-data
spec:
  storageClassName: local
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
</code></pre>

<p>When mounting a volume under docker all the folders and files from within the container are available but not in k8s.</p>

<p>Kubernetes will not automatically populate an empty volume with contents from an image.  (This is a difference from <code>docker run</code>.)  Your application needs to figure out how to set up the shared-data directory itself, if it's empty.</p>

<p>For standard database containers this doesn't really matter since they typically start off with some sort of <code>initdb</code> type call which will create the required file structure.  Similarly, if you're using a persistent volume as a cache or upload space, it doesn't matter.</p>

<p>For the use case you're describing where you want one container to just have a copy of files from the other, you don't really need a persistent volume.  I'd use an <a href="https://kubernetes.io/docs/concepts/storage/volumes/#emptydir" rel="noreferrer">emptyDir volume</a> that can be shared between the two containers, and then an <a href="https://kubernetes.io/docs/concepts/workloads/pods/init-containers/" rel="noreferrer">init container</a> to copy data into the volume.  Do not mount anything over the application content.</p>

<p>This would roughly look like (in reality use a Deployment):</p>

<pre><code>apiVersion: v1
kind: Pod
metadata:
  name: ...
spec:
  volumes:
    - name: webapp-data
      emptyDir: {}
  initContainers:
    - name: populate
      image: webapp
      volumeMounts:
        - name: webapp-data
          mountPath: /data
      command: [cp, -a, /var/www/webapp, /data]
  containers:
    - name: webapp
      image: webapp
      # no volumeMounts; default command
    - name: nginx
      image: nginx
      volumeMounts:
        - name: webapp-data
          mountPath: /var/www/html
</code></pre>

<p>With this setup there's also not a hard requirement that the two containers run in the same pod; you could have one deployment that runs the back-end service, and a second deployment that runs nginx (starting up by copying data from the back-end image).</p>

<p>(The example in <a href="https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-initialization/#creating-a-pod-that-has-an-init-container" rel="noreferrer">Configure Pod Initialization</a> in the Kubernetes docs is very similar, but fetches the nginx content from an external site.)</p>
