NFS Provisioner Setup and Testing Guide for Rancher RKE2/Kubernetes

Posted on by Malinda RathnayakeLeave a Comment on NFS Provisioner Setup and Testing Guide for Rancher RKE2/Kubernetes

This guide covers how to add an NFS StorageClass and a dynamic provisioner to Kubernetes using the nfs-subdir-external-provisioner Helm chart. This enables us to mount NFS shares dynamically for PersistentVolumeClaims (PVCs) used by workloads.

Example use cases:

  • Database migrations
  • Apache Kafka clusters
  • Data processing pipelines

Requirements:

  • An accessible NFS share exported with: rw,sync,no_subtree_check,no_root_squash
  • NFSv3 or NFSv4 protocol
  • Kubernetes v1.31.7+ or RKE2 with rke2r1 or later

 

lets get to it

1. NFS Server Export Setup

Ensure your NFS server exports the shared directory correctly:

# /etc/exports
/rke-pv-storage  worker-node-ips(rw,sync,no_subtree_check,no_root_squash)

 

  • Replace worker-node-ips with actual IPs or CIDR blocks of your worker nodes.
  • Run sudo exportfs -r to reload the export table.

2. Install NFS Subdir External Provisioner

Add the Helm repo and install the provisioned:

helm repo add nfs-subdir-external-provisioner \
  https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/
helm repo update

helm install nfs-client-provisioner \
  nfs-subdir-external-provisioner/nfs-subdir-external-provisioner \
  --namespace kube-system \
  --set nfs.server=192.168.162.100 \
  --set nfs.path=/rke-pv-storage \
  --set storageClass.name=nfs-client \
  --set storageClass.defaultClass=false

Notes:

  • If you want this to be the default storage class, change storageClass.defaultClass=true.
  • nfs.server should point to the IP of your NFS server.
  • nfs.path must be a valid exported directory from that NFS server.
  • storageClass.name can be referenced in your PersistentVolumeClaim YAMLs using storageClassName: nfs-client.

3. PVC and Pod Test

Create a test PVC and pod using the following YAML:

# test-nfs-pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-nfs-pvc
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: nfs-client
  resources:
    requests:
      storage: 1Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: test-nfs-pod
spec:
  containers:
  - name: shell
    image: busybox
    command: [ "sh", "-c", "sleep 3600" ]
    volumeMounts:
    - name: data
      mountPath: /data
  volumes:
  - name: data
    persistentVolumeClaim:
      claimName: test-nfs-pvc

 

Apply it:

kubectl apply -f test-nfs-pvc.yaml
kubectl get pvc test-nfs-pvc -w

 

Expected output:

NAME           STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
test-nfs-pvc   Bound    pvc-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx   1Gi        RWX            nfs-client     30s

 

4. Troubleshooting

If the PVC remains in Pending, follow these steps:

Check the provisioner pod status:

kubectl get pods -n kube-system | grep nfs-client-provisioner

 

Inspect the provisioner pod:

kubectl describe pod -n kube-system <pod-name>
kubectl logs -n kube-system <pod-name>

 

Common Issues:

  • Broken State: Bad NFS mount 
    mount.nfs: access denied by server while mounting 192.168.162.100:/pl-elt-kakfka

     

    • This usually means the NFS path is misspelled or not exported properly.
  • Broken State: root_squash enabled 
    failed to provision volume with StorageClass "nfs-client": unable to create directory to provision new pv: mkdir /persistentvolumes/…: permission denied

     

    • Fix by changing the export to use no_root_squash or chown the directory to nobody:nogroup.
  • ImagePullBackOff
    • Ensure nodes have internet access and can reach registry.k8s.io.
  • RBAC errors
    • Make sure the ServiceAccount used by the provisioner has permissions to watch PVCs and create PVs.

5. Healthy State Example

kubectl get pods -n kube-system | grep nfs-client-provisioner-nfs-subdir-external-provisioner
nfs-client-provisioner-nfs-subdir-external-provisioner-7992kq7m   1/1     Running     0          3m39s

 

kubectl describe pod -n kube-system nfs-client-provisioner-nfs-subdir-external-provisioner-7992kq7m
# Output shows pod is Running with Ready=True

 

kubectl logs -n kube-system nfs-client-provisioner-nfs-subdir-external-provisioner-7992kq7m
...
I0512 21:46:03.752701       1 controller.go:1420] provision "default/test-nfs-pvc" class "nfs-client": volume "pvc-73481f45-3055-4b4b-80f4-e68ffe83802d" provisioned
I0512 21:46:03.752763       1 volume_store.go:212] Trying to save persistentvolume "pvc-73481f45-3055-4b4b-80f4-e68ffe83802d"
I0512 21:46:03.772301       1 volume_store.go:219] persistentvolume "pvc-73481f45-3055-4b4b-80f4-e68ffe83802d" saved
I0512 21:46:03.772353       1 event.go:278] Event(v1.ObjectReference{Kind:"PersistentVolumeClaim", Name:"test-nfs-pvc"}): type: 'Normal' reason: 'ProvisioningSucceeded' Successfully provisioned volume pvc-73481f45-3055-4b4b-80f4-e68ffe83802d
...

 

Once test-nfs-pvc is bound and the pod starts successfully, your setup is working. You can now safely use storageClass: nfs-client in other workloads (e.g., Strimzi KafkaNodePool).

How to extend root (cs-root) Filesystem using LVM Cent OS/RHEL/Almalinux

Posted on by Malinda RathnayakeLeave a Comment on How to extend root (cs-root) Filesystem using LVM Cent OS/RHEL/Almalinux

This guide will walk you through on how to extend and increase space for the root filesystem on a alma linux. Cent OS, REHL Server/Desktop/VM

Method A – Expanding the current disk

Edit the VM and Add space to the Disk

install the cloud-utils-growpart package, as the growpart command in it makes it really easy to extend partitioned virtual disks.

sudo dnf install cloud-utils-growpart

Verify that the VM’s operating system recognizes the new increased size of the sda virtual disk, using lsblk or fdisk -l

sudo fdisk -l
Notes -
Note down the disk id and the partition number for Linux LVM - in this demo disk id is sda and lvm partition is sda 3

lets trigger a rescan of a block devices (Disks)

#elevate to root
sudo su 

#trigger a rescan, Make sure to match the disk ID you noted down before 
echo 1 > /sys/block/sda/device/rescan
exit

Now sudo fdisk -l shows the correct size of the disks

Use growpart to increase the partition size for the lvm

sudo growpart /dev/sda 3

Confirm the volume group name 

sudo vgs

Extend the logical volume 

sudo lvextend -l +100%FREE /dev/almalinux/root

Grow the file system size 

sudo xfs_growfs /dev/almalinux/root
Notes -
You can use this same steps to add space to different partitions such as home, swap if needed

Method B -Adding a second Disk to the LVM and expanding space 

Why add a second disk?
may be the the current Disk is locked due to a snapshot and you cant remove it, Only solution would be to add a second disk/

Check the current space available 

sudo df -h 
Notes -
If you have 0% ~1MB left on the cs-root command auto-complete with tab and some of the later commands wont work, You should clear up atleast 4-10mb by clearing log files, temp files, etc

Mount an additional disk to the VM (Assuming this is a VM) and make sure the disk is visible on the OS level

sudo lvmdiskscan

OR

sudo fdisk -l

Confirm the volume group name 

sudo vgs

Lets increase the space

First lets initialize the new disk we mounted

sudo mkfs.xfs /dev/sdb

Create the Physical volume 

sudo pvcreate /dev/sdb

extend the volume group 

sudo vgextend cs /dev/sdb
  Volume group "cs" successfully extended


Extend the logical volume 

sudo lvextend -l +100%FREE /dev/cs/root

Grow the file system size 

sudo xfs_growfs /dev/cs/root

Confirm the changes 

sudo df -h

Just making easy for us!!

#Method A - Expanding the current disk 
#AlmaLinux
sudo dnf install cloud-utils-growpart

sudo lvmdiskscan
sudo fdisk -l                          #note down the disk ID and partition num


sudo su                                #elevate to root
echo 1 > /sys/block/sda/device/rescan  #trigger a rescan
exit                                   #exit root shell

sudo lvextend -l +100%FREE /dev/almalinux/root
sudo xfs_growfs /dev/almalinux/root
sudo df -h

#Method B - Adding a second Disk 
#CentOS

sudo lvmdiskscan
sudo fdisk -l
sudo vgs
sudo mkfs.xfs /dev/sdb
sudo pvcreate /dev/sdb
sudo vgextend cs /dev/sdb
sudo lvextend -l +100%FREE /dev/cs/root
sudo xfs_growfs /dev/cs/root
sudo df -h

#AlmaLinux

sudo lvmdiskscan
sudo fdisk -l
sudo vgs
sudo mkfs.xfs /dev/sdb
sudo pvcreate /dev/sdb
sudo vgextend almalinux /dev/sdb
sudo lvextend -l +100%FREE /dev/almalinux/root
sudo xfs_growfs /dev/almalinux/root
sudo df -h