Installing Longhorn Storage on Kubernetes

Longhorn is a distributed block storage system for Kubernetes. It replicates volumes across nodes using local disks. These notes cover installation with Helm on RHEL-family nodes such as Rocky Linux.

Pre-flight

Install the packages Longhorn needs on every node. iSCSI is used to attach volumes, and NFS is needed for ReadWriteMany volumes and backups:

dnf install iscsi-initiator-utils jq nfs-utils
systemctl enable --now iscsid

Load the iscsi_tcp kernel module now and at every boot:

modprobe iscsi_tcp
echo iscsi_tcp | sudo tee /etc/modules-load.d/iscsi_tcp.conf

Then run Longhorn’s environment check script, which reports any missing dependency:

curl -sSL https://raw.githubusercontent.com/longhorn/longhorn/refs/tags/v1.7.2/scripts/environment_check.sh | bash

Helm install

helm repo add longhorn https://charts.longhorn.io --force-update
helm install longhorn longhorn/longhorn --namespace longhorn-system --create-namespace --version 1.7.2

Custom installation

To change the defaults, download the chart’s values.yaml, edit it, and install with it:

curl -Lo values.yaml https://raw.githubusercontent.com/longhorn/charts/master/charts/longhorn/values.yaml

helm install longhorn longhorn/longhorn \
  --namespace longhorn-system \
  --create-namespace \
  --values values.yaml

To apply changes to values.yaml later without changing the Longhorn version, upgrade to the version that is already installed:

helm upgrade longhorn longhorn/longhorn --namespace longhorn-system --values ./values.yaml --version `helm list -n longhorn-system -o json | jq -r .'[0].app_version'`

Storage class

The chart creates a longhorn StorageClass and makes it the default. To use other settings, such as fewer replicas on a small cluster, create another StorageClass:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: longhorn-single
provisioner: driver.longhorn.io
allowVolumeExpansion: true
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
  numberOfReplicas: "1"
  staleReplicaTimeout: "2880"
  fsType: ext4
  dataLocality: best-effort

Reference it from a PersistentVolumeClaim with storageClassName: longhorn-single.