If you you need a simplest to share the file and your pods are in the same node, you could use hostpath to store the file and share the volume with other 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:

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.

References: Configure persistent volumes Persistent volumes Volume Types