One of the easiest ways to achieve improved persistence amid container crashes and data sharing within a pod is to use the emptydir volume. This volume type can be used with either the storage volumes of the node machine itself or an optional RAM disk for higher performance.

Again, we improve our persistence beyond a single container, but when a pod is removed, the data will be lost. A machine reboot will also clear any data from RAM-type disks. There may be times when we just need some shared temporary space or have containers that process data and hand it off to another container before they die. Whatever the case, here is a quick example of using this temporary disk with the RAM-backed option.

Open your favorite editor and create a storage-memory.yaml file and type the following code:

apiVersion: v1 
kind: Pod 
metadata: 
  name: memory-pd 
spec: 
  containers: 
  - image: nginx:latest 
    ports: 
    - containerPort: 80 
    name: memory-pd 
    volumeMounts: 
    - mountPath: /memory-pd 
      name: memory-volume 
  volumes: 
  - name: memory-volume 
    emptyDir: 
      medium: Memory 

The preceding example is probably second nature by now, but we will once again issue a create command followed by an exec command to see the folders in the container:

$ kubectl create -f storage-memory.yaml
$ kubectl exec memory-pd -- ls -lh | grep memory-pd

This will give us a Bash shell in the container itself. The ls command shows us a memory-pd folder at the top level. We use grep to filter the output, but you can run the command without | grep memory-pd to see all folders:

Again, this folder is temporary as everything is stored in the node's (minion's) RAM. When the node gets restarted, all the files will be erased. We will look at a more permanent example next.