rancher-charts/charts/longhorn/README.md

# Longhorn Chart

> **Important**: Please install the Longhorn chart in the `longhorn-system` namespace only.

> **Warning**: Longhorn doesn't support downgrading from a higher version to a lower version.

## Source Code

Longhorn is 100% open source software. Project source code is spread across a number of repos:

1. Longhorn Engine -- Core controller/replica logic https://github.com/longhorn/longhorn-engine
2. Longhorn Instance Manager -- Controller/replica instance lifecycle management https://github.com/longhorn/longhorn-instance-manager
3. Longhorn Share Manager -- NFS provisioner that exposes Longhorn volumes as ReadWriteMany volumes. https://github.com/longhorn/longhorn-share-manager
4. Longhorn Manager -- Longhorn orchestration, includes CSI driver for Kubernetes https://github.com/longhorn/longhorn-manager
5. Longhorn UI -- Dashboard https://github.com/longhorn/longhorn-ui

## Prerequisites

1. Docker v1.13+
2. Kubernetes v1.16+
3. Make sure `curl`, `findmnt`, `grep`, `awk` and `blkid` has been installed in all nodes of the Kubernetes cluster.
4. Make sure `open-iscsi` has been installed in all nodes of the Kubernetes cluster. For GKE, recommended Ubuntu as guest OS image since it contains `open-iscsi` already.

## Uninstallation

To prevent damage to the Kubernetes cluster, we recommend deleting all Kubernetes workloads using Longhorn volumes (PersistentVolume, PersistentVolumeClaim, StorageClass, Deployment, StatefulSet, DaemonSet, etc).

From Rancher Cluster Explorer UI, navigate to Apps page, delete app `longhorn` then app `longhorn-crd` in Installed Apps tab.


---
Please see [link](https://github.com/longhorn/longhorn) for more information.