I have created a Kubernetes read-only many persistent volume from a gcePersistentDisk like so:
apiVersion: v1
kind: PersistentVolume
metadata:
name: ferret-pv-1
spec:
capacity:
storage: 500Gi
accessModes:
- ReadOnlyMany
persistentVolumeReclaimPolicy: Retain
gcePersistentDisk:
pdName: data-1
partition: 1
fsType: ext4
It creates the persistent volume from the existing gcePersistentDisk partition which already has an ext4 filesystem on it:
$ kubectl get pv
NAME CAPACITY ACCESSMODES RECLAIMPOLICY STATUS CLAIM REASON AGE
ferret-pv-1 500Gi ROX Retain Bound default/ferret-pvc 5h
I then create a Kubernetes read-only many persistent volume claim like so:
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: ferret-pvc
spec:
accessModes:
- ReadOnlyMany
resources:
requests:
storage: 500Gi
It binds to the read-only PV I created above:
$ kubectl get pvc
NAME STATUS VOLUME CAPACITY ACCESSMODES AGE
ferret-pvc Bound ferret-pv-1 500Gi ROX 5h
I then create a Kubernetes deployment with 2 replicas using the PVC I just created like so:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: ferret2-deployment
spec:
replicas: 2
template:
metadata:
labels:
name: ferret2
spec:
containers:
- image: us.gcr.io/centered-router-102618/ferret2
name: ferret2
ports:
- name: fjds
containerPort: 1004
hostPort: 1004
volumeMounts:
- name: ferret-pd
mountPath: /var/ferret
readOnly: true
volumes:
- name: ferret-pd
persistentVolumeClaim:
claimName: ferret-pvc
The deployment is created:
$ kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
ferret2-deployment 2 2 2 1 4h
However, when I look at the corresponding two pods from the deployment, only the first one came up:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
ferret2-deployment-1336109949-2rfqd 1/1 Running 0 4h
ferret2-deployment-1336109949-yimty 0/1 ContainerCreating 0 4h
Looking at the second pod which didn't come up:
$ kubectl describe pod ferret2-deployment-1336109949-yimty
Events:
FirstSeen LastSeen Count From SubObjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
4h 1m 128 {kubelet gke-sim-cluster-default-pool-e38a7605-kgdu} Warning FailedMount Unable to mount volumes for pod "ferret2-deployment-1336109949-yimty_default(d1393a2d-9fc9-11e6-a873-42010a8a009e)": timeout expired waiting for volumes to attach/mount for pod "ferret2-deployment-1336109949-yimty"/"default". list of unattached/unmounted volumes=[ferret-pd]
4h 1m 128 {kubelet gke-sim-cluster-default-pool-e38a7605-kgdu} Warning FailedSync Error syncing pod, skipping: timeout expired waiting for volumes to attach/mount for pod "ferret2-deployment-1336109949-yimty"/"default". list of unattached/unmounted volumes=[ferret-pd]
4h 55s 145 {controller-manager } Warning FailedMount Failed to attach volume "ferret-pv-1" on node "gke-sim-cluster-default-pool-e38a7605-kgdu" with: googleapi: Error 400: The disk resource 'data-1' is already being used by 'gke-sim-cluster-default-pool-e38a7605-fyx4'
It's refusing to start up the second pod because it thinks the first one has exclusive use of the PV. However, when I login to the first pod which claimed the PV, I see it has mounted the volume as read-only:
$ kubectl exec -ti ferret2-deployment-1336109949-2rfqd -- bash
root@ferret2-deployment-1336109949-2rfqd:/opt/ferret# mount | grep ferret
/dev/sdb1 on /var/ferret type ext4 (ro,relatime,data=ordered)
Am I missing something regarding mounting a PV read-only across multiple pods in a deployment using the same PVC? The disk is not mounted by any other containers. Since it mounted read-only on the first pod I would have expected the second and any other replicas in the deployment to have no problem claiming/mounting it. Also - how would I get ReadWriteOnce to work properly and how do I specify which pod mounts the volume rw?
