elasticsearch.yml is read-only when loaded using Kubernetes ConfigMap - docker

Question

I am trying to load elasticsearch.yml file using ConfigMap while installing ElasticSearch using Kubernetes.
kubectl create configmap elastic-config --from-file=./elasticsearch.yml
The elasticsearch.yml file is loaded in the container with root as its owner and read-only permission (https://github.com/kubernetes/kubernetes/issues/62099). Since, ElasticSearch will not start with root ownership, the pod crashes.
As a work-around, I tried to mount the ConfigMap to a different file and then copy it to the config directory using an initContainer. However, the file in the config directory does not seem to be updated.
Is there anything that I am missing or is there any other way to accomplish this?
ElasticSearch Kubernetes StatefulSet:
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: es-cluster
labels:
app: elasticservice
spec:
serviceName: elasticsearch
replicas: 1
selector:
matchLabels:
app: elasticsearch
template:
metadata:
labels:
app: elasticsearch
spec:
containers:
- name: elasticsearch
image: docker.elastic.co/elasticsearch/elasticsearch:6.5.4
resources:
limits:
cpu: 1000m
requests:
cpu: 100m
ports:
- containerPort: 9200
name: rest
protocol: TCP
- containerPort: 9300
name: inter-node
protocol: TCP
volumeMounts:
- name: elastic-config-vol
mountPath: /tmp/elasticsearch
- name: elastic-storage
mountPath: /usr/share/elasticsearch/data
env:
- name: cluster.name
value: docker-elastic
- name: node.name
valueFrom:
fieldRef:
fieldPath: metadata.name
- name: discovery.zen.ping.unicast.hosts
value: "elastic-service"
- name: discovery.zen.minimum_master_nodes
value: "1"
- name: node.master
value: "true"
- name: node.data
value: "true"
- name: ES_JAVA_OPTS
value: "-Xmx256m -Xms256m"
volumes:
- name: elastic-config-vol
configMap:
name: elastic-config
items:
- key: elasticsearch.yml
path: elasticsearch.yml
- name: elastic-config-dir
emptyDir: {}
- name: elastic-storage
emptyDir: {}
initContainers:
# elasticsearch will not run as non-root user, fix permissions
- name: fix-vol-permission
image: busybox
command:
- sh
- -c
- chown -R 1000:1000 /usr/share/elasticsearch/data
securityContext:
privileged: true
volumeMounts:
- name: elastic-storage
mountPath: /usr/share/elasticsearch/data
- name: fix-config-vol-permission
image: busybox
command:
- sh
- -c
- cp /tmp/elasticsearch/elasticsearch.yml /usr/share/elasticsearch/config/elasticsearch.yml
securityContext:
privileged: true
volumeMounts:
- name: elastic-config-dir
mountPath: /usr/share/elasticsearch/config
- name: elastic-config-vol
mountPath: /tmp/elasticsearch
# increase default vm.max_map_count to 262144
- name: increase-vm-max-map-count
image: busybox
command:
- sysctl
- -w
- vm.max_map_count=262144
securityContext:
privileged: true
- name: increase-the-ulimit
image: busybox
command:
- sh
- -c
- ulimit -n 65536
securityContext:
privileged: true

Answer 1

I use:
...
volumeMounts:
- name: config
mountPath: /usr/share/elasticsearch/config/elasticsearch.yml
subPath: elasticsearch.yml
volumes:
- name : config
configMap:
name: es-configmap
without any permissions problem, but you can set permissions with defaultMode