Unable to mount NFS on Kubernetes Pod - kubernetes

Question

I am working on deploying Hyperledger Fabric test network on Kubernetes minikube cluster. I intend to use PersistentVolume to share cytpo-config and channel artifacts among various peers and orderers. Following is my PersistentVolume.yaml and PersistentVolumeClaim.yaml
kind: PersistentVolume
apiVersion: v1
metadata:
name: persistent-volume
spec:
capacity:
storage: 1Gi
accessModes:
- ReadWriteMany
nfs:
path: "/nfsroot"
server: "3.128.203.245"
readOnly: false
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: persistent-volume-claim
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
Following is the pod where the above claim is mount on /data
kind: Pod
apiVersion: v1
metadata:
name: test-shell
labels:
name: test-shell
spec:
containers:
- name: shell
image: ubuntu
command: ["/bin/bash", "-c", "while true ; do sleep 10 ; done"]
volumeMounts:
- mountPath: "/data"
name: pv
volumes:
- name: pv
persistentVolumeClaim:
claimName: persistent-volume-claim
NFS is setup on my EC2 instance. I have verified NFS server is working fine and I was able to mount it inside minikube. I am not understanding what wrong am I doing, but any file present inside 3.128.203.245:/nfsroot is not present in test-shell:/data
What point am I missing. I even tried hostPath mount but to no avail. Please help me out.

Answer 1

I think you should check the following things to verify that NFS is mounted successfully or not
run this command on the node where you want to mount.
$showmount -e nfs-server-ip
like in my case $showmount -e 172.16.10.161
Export list for 172.16.10.161:
/opt/share *
use $df -hT command see that Is NFS is mounted or not like in my case it will give output 172.16.10.161:/opt/share nfs4 91G 32G 55G 37% /opt/share
if not mounted then use the following command
$sudo mount -t nfs 172.16.10.161:/opt/share /opt/share
if the above commands show an error then check firewall is allowing nfs or not
$sudo ufw status
if not then allow using the command
$sudo ufw allow from nfs-server-ip to any port nfs
I made the same setup I don't face any issues. My k8s cluster of fabric is running successfully . The hf k8s yaml files can be found at my GitHub repo. There I have deployed the consortium of Banks on hyperledger fabric which is a dynamic multihost blockchain network that means you can add orgs, peers, join peers, create channels, install and instantiate chaincode on the go in an existing running blockchain network.

Answer 2

By default in minikube you should have default StorageClass:
Each StorageClass contains the fields provisioner, parameters, and reclaimPolicy, which are used when a PersistentVolume belonging to the class needs to be dynamically provisioned.
For example, NFS doesn't provide an internal provisioner, but an external provisioner can be used. There are also cases when 3rd party storage vendors provide their own external provisioner.
Change the default StorageClass
In your example this property can lead to problems.
In order to list enabled addons in minikube please use:
minikube addons list
To list all StorageClasses in your cluster use:
kubectl get sc
NAME PROVISIONER
standard (default) k8s.io/minikube-hostpath
Please note that at most one StorageClass can be marked as default. If two or more of them are marked as default, a PersistentVolumeClaim without storageClassName explicitly specified cannot be created.
In your example the most probable scenario is that you have already default StorageClass. Applying those resources caused: new PV creation (without StoraglClass), new PVC creation (with reference to existing default StorageClass). In this situation there is no reference between your custom pv/pvc binding) as an example please take a look:
kubectl get pv,pvc,sc
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
persistentvolume/nfs 3Gi RWX Retain Available 50m
persistentvolume/pvc-8aeb802f-cd95-4933-9224-eb467aaa9871 1Gi RWX Delete Bound default/pvc-nfs standard 50m
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
persistentvolumeclaim/pvc-nfs Bound pvc-8aeb802f-cd95-4933-9224-eb467aaa9871 1Gi RWX standard 50m
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
storageclass.storage.k8s.io/standard (default) k8s.io/minikube-hostpath Delete Immediate false 103m
This example will not work due to:
new persistentvolume/nfs has been created (without reference to pvc)
new persistentvolume/pvc-8aeb802f-cd95-4933-9224-eb467aaa9871 has been created using default StorageClass. In the Claim section we can notice that this pv has been created due to dynamic pv provisioning using default StorageClass with reference to default/pvc-nfs claim (persistentvolumeclaim/pvc-nfs ).
Solution 1.
According to the information from the comments:
Also I am able to connect to it within my minikube and also my actual ubuntu system.
I you are able to mount from inside minikube host this nfs share
If you mounted nfs share into your minikube node, please try to use this example with hostpath volume directly from your pod:
apiVersion: v1
kind: Pod
metadata:
name: test-shell
namespace: default
spec:
volumes:
- name: pv
hostPath:
path: /path/shares # path to nfs mount point on minikube node
containers:
- name: shell
image: ubuntu
command: ["/bin/bash", "-c", "sleep 1000 "]
volumeMounts:
- name: pv
mountPath: /data
Solution 2.
If you are using PV/PVC approach:
kind: PersistentVolume
apiVersion: v1
metadata:
name: persistent-volume
spec:
capacity:
storage: 1Gi
accessModes:
- ReadWriteOnce
storageClassName: "" # Empty string must be explicitly set otherwise default StorageClass will be set / or custom storageClassName name
nfs:
path: "/nfsroot"
server: "3.128.203.245"
readOnly: false
claimRef:
name: persistent-volume-claim
namespace: default
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: persistent-volume-claim
namespace: default
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
storageClassName: "" # Empty string must be explicitly set otherwise default StorageClass will be set / or custom storageClassName name
volumeName: persistent-volume
Note:
If you are not referencing any provisioner associated with your StorageClass
Helper programs relating to the volume type may be required for consumption of a PersistentVolume within a cluster. In this example, the PersistentVolume is of type NFS and the helper program /sbin/mount.nfs is required to support the mounting of NFS filesystems.
Please keep in mind that when you are creating pvc kubernetes persistent-controller is trying to bind pvc with proper pv. During this process different factors are take into account like: storageClassName (default/custom), accessModes, claimRef, volumeName.
In this case you can use:
PersistentVolume.spec.claimRef.name: persistent-volume-claim PersistentVolumeClaim.spec.volumeName: persistent-volume
Note:
The control plane can bind PersistentVolumeClaims to matching PersistentVolumes in the cluster. However, if you want a PVC to bind to a specific PV, you need to pre-bind them.
By specifying a PersistentVolume in a PersistentVolumeClaim, you declare a binding between that specific PV and PVC. If the PersistentVolume exists and has not reserved PersistentVolumeClaims through its claimRef field, then the PersistentVolume and PersistentVolumeClaim will be bound.
The binding happens regardless of some volume matching criteria, including node affinity. The control plane still checks that storage class, access modes, and requested storage size are valid.
Once the PV/pvc were created or in case of any problem with pv/pvc binding please use the following commands to figure current state:
kubectl get pv,pvc,sc
kubectl describe pv
kubectl describe pvc
kubectl describe pod
kubectl get events