https://github.com/kubernetes/kubernetes/issues/24215

k8s-test-configmap.sh

#!/bin/bash

echo "
this script

1) creates a configmap: test-configmap-configmap
2) creates a pod: test-configmap-busybox which mounts the configmap as volume
3) checks the modification-time of the file inside the volume -> m1
4) changes the data of test-configmap-configmap and waits until the content 
   of the file changes
5) checks the modification-time of the file inside the volume -> m2

now m1 should be older then m2, but it is not
"

# make sure test-resources dont exist
echo "make sure test-resource configmap doesnt exist"
while $(kubectl get configmap test-configmap-configmap &> /dev/null); do
  kubectl delete configmap test-configmap-configmap &> /dev/null
  sleep 1
done
echo "make sure test-resource busybox doesnt exist"
while $(kubectl get po test-configmap-busybox &> /dev/null); do
  kubectl delete po test-configmap-busybox &> /dev/null
  sleep 1
done


echo "========================================= 1"

echo "
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-configmap-configmap
data:
  some-file.txt: |
    version:1
" | kubectl create -f -

echo "========================================= 2"

echo '
apiVersion: v1
kind: Pod
metadata:
  name: test-configmap-busybox
spec:
  containers:
  - name: busybox
    image: busybox
    command: ["/bin/sh", "-c", "while true; do sleep 3600; done"]
    volumeMounts:
    - name: data
      mountPath: /test
      readOnly: true
  volumes:
  - name: data
    configMap:
      name: test-configmap-configmap
' | kubectl create -f -

until $(kubectl exec test-configmap-busybox date &> /dev/null); do sleep 1; done

echo "========================================= 3"

kubectl exec test-configmap-busybox -- cat /test/some-file.txt
kubectl exec test-configmap-busybox -- ls -al /test
MODTIME_1=$(kubectl exec test-configmap-busybox -- stat /test/some-file.txt | grep "^Modify")

echo "========================================= 4"

echo "
apiVersion: v1
kind: ConfigMap
metadata:
  name: test-configmap-configmap
data:
  some-file.txt: |
    version:2
" | kubectl apply -f -

echo "waiting for file content to change"
CONTENT=$(kubectl exec test-configmap-busybox -- cat /test/some-file.txt)
declare -i n=0
while [ $CONTENT != "version:2" ]; do
  echo -n .
  sleep 1
  n=$n+1
  CONTENT=$(kubectl exec test-configmap-busybox -- cat /test/some-file.txt)
  # echo -n $CONTENT
done
echo "$n seconds"

echo "========================================= 5"

MODTIME_2=$(kubectl exec test-configmap-busybox -- stat /test/some-file.txt | grep "^Modify")


echo "modtime 1: "$MODTIME_1
echo "modtime 2: "$MODTIME_2

echo "========================================="
echo "now you will enter pod:test-configmap-busybox"
echo "all resources will be cleaned up on exit"
kubectl exec -ti test-configmap-busybox sh

kubectl delete po test-configmap-busybox
kubectl delete configmap test-configmap-configmap

$ ./test-configmap.sh

this script

1) creates a configmap: test-configmap-configmap
2) creates a pod: test-configmap-busybox which mounts the configmap as volume
3) checks the modification-time of the file inside the volume -> m1
4) changes the data of test-configmap-configmap and waits until the content
   of the file changes
5) checks the modification-time of the file inside the volume -> m2

now m1 should be older then m2, but it is not

make sure test-resource configmap doesnt exist
make sure test-resource busybox doesnt exist
========================================= 1
configmap "test-configmap-configmap" created
========================================= 2
pod "test-configmap-busybox" created
========================================= 3
version:1
total 4
drwxrwxrwt    3 root     root           100 Apr 13 21:00 .
drwxr-xr-x   20 root     root          4096 Apr 13 21:00 ..
drwx------    2 root     root            60 Apr 13 21:00 ..4984_13_04_23_00_44.228447895
lrwxrwxrwx    1 root     root            31 Apr 13 21:00 ..data -> ..4984_13_04_23_00_44.228447895
lrwxrwxrwx    1 root     root            20 Apr 13 21:00 some-file.txt -> ..data/some-file.txt
========================================= 4
configmap "test-configmap-configmap" configured
waiting for file content to change
..................................................50 seconds
========================================= 5
modtime 1: Modify: 2016-04-13 21:00:44.000000000
modtime 2: Modify: 2016-04-13 21:00:44.000000000
=========================================
now you will enter pod:test-configmap-busybox
all resources will be cleaned up on exit
/ # exit
pod "test-configmap-busybox" deleted
configmap "test-configmap-configmap" deleted