Example for https://www.reddit.com/r/kubernetes/comments/8m0xvv/copying_a_file_from_the_host_to_the_container/

pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: example
  spec:
    initContainers:
      - name: file-copy
        image: busybox:latest
        command:
          - cp
          - /src/big-file
          - /dst/
        volumeMounts:
          - name: source
            mountPath: /src
          - name: destination
            mountPath: /dst
  containers:
    - name: app
      image: alpine:latest
      command:
        - bash
        - -c
        - "stat /data/big-file; sleep 300"
      volumeMounts:
        - name: destination
          mountPath: /data/
  volumes:
    - name: source
      hostPath:
        path: /home/some-user/big-file
    - name: destination
      emptyDir: {}