Replacing a properties file within a kubernetes container

While spinning a Nifi cluster on Azure Kubernetes Service, I faced issue while mounting the nifi.properties file on using configMap. While using the following configuration for mounting a file, I am getting the following error.

sed: can't move '/opt/nifi/conf/nifi.propertiesnCjDfm' to '/opt/nifi/conf/nifi.properties': Resource busy

This error seems to be happening due to the nifi instance already utilizing the file before kubernetes had a chance to replace it.

I am looking for an alternative or a better way to configure nifi cluster and managing its configuration. Currently I was attempting to use ConfigMap to store the nifi.properties or any other files necessary.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: nifi
  namespace: nifi-ns
  ...
spec:
  template:
    spec:
      containers:
      - name: nifi
        image: xemuliam/nifi:1.9.1
        ...
        volumeMounts:
        ...
        - mountPath: /opt/nifi/conf/nifi.properties
          subPath: nifi.properties
          name: file
      volumes:
      - name: file
        configMap:
            name: nifi-properties-cm
            items:
            - key: nifi.properties
              path: nifi.properties

Following is my configMap:

apiVersion: v1
kind: ConfigMap
metadata:
  name: nifi-properties-cm
  namespace: nifi-ns
data:
  nifi.properties: |
    # Core Properties #
    nifi.flow.configuration.file=./conf/flow.xml.gz
    ...

I've tried mounting the file like above also tried to mount the entire conf folder (I donot like this way as the only configuration I will really wanna change is the nifi.properties)

I know I could always customize the image and give a custom entrypoint to achieve the same effect but I'd like to try and solve the problem using kubernetes alone. Is there any other way I can solve this? Is there any suggested best practice or best way of solving this problem?

UPDATE:

Based on the comments provided below, I've tried creating an init container and copying a file to a shared volume but that does not help as it overwrites the folder within container and makes the pod fail.

Here is the config used:

apiVersion: v1
kind: Pod
metadata:
  name: test
  labels:
    name: test
spec:
  initContainers:
  - name: busybox
    image: busybox
    command: ["/bin/sh", "-c", "cp /usr/nifi.properties /opt/nifi/conf/nifi.properties"]
    volumeMounts:
    - mountPath: /usr/nifi.properties
      name: file
      subPath: nifi.properties
    - mountPath: /opt/nifi/conf
      name: config
  containers:
  - name: test
    image: xemuliam/nifi:1.9.1
    resources:
      limits:
        memory: "128Mi"
        cpu: "500m"
    ports:
    - containerPort: 80
    volumeMounts:
      - mountPath: /opt/nifi/conf
        name: config
  volumes:
  - name: file
    configMap:
        name: nifi-properties-cm
  - name: config
    emptyDir: {}

Here is the application logs I receive:

Exception in thread "main" java.io.FileNotFoundException: /opt/nifi/conf/bootstrap.conf (No such file or directory)
    at java.io.FileInputStream.open0(Native Method)
    at java.io.FileInputStream.open(FileInputStream.java:195)
    at java.io.FileInputStream.<init>(FileInputStream.java:138)
    at org.apache.nifi.bootstrap.RunNiFi.loadServices(RunNiFi.java:267)
    at org.apache.nifi.bootstrap.RunNiFi.<init>(RunNiFi.java:152)
    at org.apache.nifi.bootstrap.RunNiFi.main(RunNiFi.java:212)