While making a NFS or any cloud backed storage we Will require some
additional components. We need to create a Persistent Volume and Persistent
volume Claim for using the volumes
PersistentVolumeClaim - Binding between a Pod and Persistent
Volume
Volume Driver - code that will be used to communicate
with the back end storage
StorageClass - Allows dynamic provisioning of
Persistent volume
Lets create a Persistent Volume,
[root@manja17-I13330 kubenetes-config]# cat nfs-pv.yml
apiVersion: v1
kind: PersistentVolume
metadata:
name: test-nfs
spec:
capacity:
storage: 1Mi
accessModes:
- ReadWriteMany
nfs:
server: 10.131.175.138
path: "/nfsshare"
In the above config, we are actually using a nfs volume from the ip
address “10.131.175.138” where nfs shares where already created under the
/nfsshare. Run this and see how it works
[root@manja17-I13330 kubenetes-config]# kubectl create -f nfs-pv.yml
persistentvolume "test-nfs" created
If we check the mount command from our worker nodes we can see the
below output, [root@manja17-I14021 nfsshare]# mount | grep nfsshare
10.131.175.138:/nfsshare on /mnt/nfsshare type nfs4
(rw,relatime,vers=4.1,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=10.131.36.181,local_lock=none,addr=10.131.175.138)
We can see that the /nfsshare from 10.131.165.138 is mounted onto the
/mnt/nfssshare on the worker nodes. In the above case we are creating a
persistent volume with 1MI size
Now lets create a PersistentVolumeClaim -
[root@manja17-I13330 kubenetes-config]# cat nfs-pvc.yml
kind: PersistentVolumeClaim
apiVersion: v1
metadata:
name: test-nfs
spec:
accessModes:
- ReadWriteMany
resources:
requests:
storage: 1Mi
The Persistent volume claim works in different way. In the above
configuration we are asking K8 to provide us a volume which has storage of 1MI.
We are not calling the persistent volume directly rather we are creating a
persistent Volume claim and giving K8 the authority of identifying the volumes
with the size that we requested.if that finds with a pv with that volume it
allocates that to the pod.
Sample Pod Configuration - Now lets create a Pod which will use the
NFS volume
[root@manja17-I13330 kubenetes-config]# cat nfs-pod.yml
apiVersion: v1
metadata:
name: nfs-web
spec:
replicas: 1
selector:
role: web-frontend
template:
metadata:
labels:
role: web-frontend
spec:
containers:
- name: web
image: nginx
ports:
- name: web
containerPort: 80
volumeMounts:
# name must match
the volume name below
- name: test-nfs
mountPath:
"/usr/share/nginx/html"
volumes:
- name: test-nfs
persistentVolumeClaim:
claimName: test-nfs
In the above pod configuration, the main elements are Volumes and
Volume mounts. The volume element contains the Persistent Volume claim details
that we created earlier. The Volume mount is the place where if volume with our
requirement is available it will mount on the location /usr/share/nginx/html
inside the container.
Run the Container and see how it works -
[root@manja17-I13330 kubenetes-config]# kubectl get pods
NAME READY
STATUS RESTARTS AGE
nfs-web-qk2qn 1/1
Running 0 4m
[root@manja17-I13330 kubenetes-config]# kubectl exec -it nfs-web-qk2qn
-- bash
root@nfs-web-qk2qn:/# cd /usr/share/nginx/html/
root@nfs-web-qk2qn:/usr/share/nginx/html# touch container.txt
root@nfs-web-qk2qn:/usr/share/nginx/html# cat container.txt
root@nfs-web-qk2qn:/usr/share/nginx/html# echo "this is from
container" >> container.txt
root@nfs-web-qk2qn:/usr/share/nginx/html# cat container.txt
this is from container
root@nfs-web-qk2qn:/usr/share/nginx/html# exit
exit
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