Adding Persistent Volume Claim to the existing file in Container - docker

Question

In my docker image I have a directory /opt/myapp/etc which has some files and directories. I want to create statefulset for my app. In that statefulset I am creating persistent volume claim and attach to /opt/myapp/etc. Statefulset yaml is attached below. Can anyone tell me how to attach volume to container in this case?
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: statefulset
labels:
app: myapp
spec:
serviceName: myapp
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
containers:
- image: 10.1.23.5:5000/redis
name: redis
ports:
- containerPort: 6379
name: redis-port
- image: 10.1.23.5:5000/myapp:18.1
name: myapp
ports:
- containerPort: 8181
name: port
volumeMounts:
- name: data
mountPath: /opt/myapp/etc
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: [ "ReadWriteOnce" ]
storageClassName: standard
resources:
requests:
storage: 5Gi
Here is the output of describe pod
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Warning FailedScheduling 3m (x4 over 3m) default-scheduler pod has unbound PersistentVolumeClaims
Normal Scheduled 3m default-scheduler Successfully assigned controller-statefulset-0 to dev-k8s-2
Normal SuccessfulMountVolume 3m kubelet, dev-k8s-2 MountVolume.SetUp succeeded for volume "default-token-xpskd"
Normal SuccessfulAttachVolume 3m attachdetach-controller AttachVolume.Attach succeeded for volume "pvc-77d2cef8-a674-11e8-9358-fa163e3294c1"
Normal SuccessfulMountVolume 3m kubelet, dev-k8s-2 MountVolume.SetUp succeeded for volume "pvc-77d2cef8-a674-11e8-9358-fa163e3294c1"
Normal Pulling 2m kubelet, dev-k8s-2 pulling image "10.1.23.5:5000/redis"
Normal Pulled 2m kubelet, dev-k8s-2 Successfully pulled image "10.1.23.5:5000/redis"
Normal Created 2m kubelet, dev-k8s-2 Created container
Normal Started 2m kubelet, dev-k8s-2 Started container
Normal Pulled 1m (x4 over 2m) kubelet, dev-k8s-2 Container image "10.1.23.5:5000/myapp:18.1" already present on machine
Normal Created 1m (x4 over 2m) kubelet, dev-k8s-2 Created container
Normal Started 1m (x4 over 2m) kubelet, dev-k8s-2 Started container
Warning BackOff 1m (x7 over 2m) kubelet, dev-k8s-2 Back-off restarting failed container
storageclass definition
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
name: standard
namespace: controller
provisioner: kubernetes.io/cinder
reclaimPolicy: Retain
parameters:
availability: nova

Answer 1

check if you have storage class defined in your cluster.
kubectl get storageclass
If your are using default storage class as host-path(in case of minikube) then you do not need to include storage class into your template.
volumeClaimTemplates:
- metadata:
name: data
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 5Gi
by specifying no storage class k8s will go ahead and schedule the persistent volume with the default storage class which would be host-path in case of minikube also make sure /opt/myapp/etc exist on the node where pod is going to be scheduled.

Answer 2

Kubernetes will not allow the mounting 2 volumes to a same directory. second mount will overwrite the files created by the first.
In my case docker image had some files in etc directory, which were removed after mounting the volume. Solved the problem using subpath.