doc(os/distro): OCP/OKD support

content/docs/1.6.0/advanced-resources/os-distro-specific/okd-support.md

@@ -0,0 +1,114 @@
+---
+title:  OCP/OKD Support
+weight: 4
+---
+
+To deploy Longhorn on a cluster provisioned with OpenShift 4.x, some additional configurations are required.
+
+- [Install Longhorn](#install-longhorn)
+- [Prepare A Customized Default Longhorn Disk (Optional)](#prepare-a-customized-default-longhorn-disk-optional)
+  - [Add An Extra Disk to Longhorn Storage](#add-an-extra-disk-to-longhorn-storage)
+    - [Create Filesystem For The Device](#create-filesystem-for-the-device)
+    - [Mounting The Device On Boot with MachineConfig CRD](#mounting-the-device-on-boot-with-machineconfig-crd)
+    - [Label and Annotate The Node](#label-and-annotate-the-node)
+- [Reference](#reference)
+- [Main Contributor](#main-contributor)
+
+## Install Longhorn
+
+Please refer to this section [Install with Helm](../../../deploy/install/install-with-helm/) first.
+
+And then install Longhorn with setting ***openshift.enabled*** true:
+
+```bash
+  helm install longhorn longhorn/longhorn --namespace longhorn-system --create-namespace --set openshift.enabled=true
+```
+
+## Prepare A Customized Default Longhorn Disk (Optional)
+
+To understand more about configuring the disks for Longhorn, please refer to the section [Configuring Defaults for Nodes and Disks](../../../advanced-resources/default-disk-and-node-config/#launch-longhorn-with-multiple-disks)
+
+Longhorn will use the directory `/var/lib/longhorn` as default storage mount point and that means Longhorn use the root device as the default storage. If you don't want to use the root device as the Longhorn storage, set ***defaultSettings.createDefaultDiskLabeledNodes*** true when installing Longhorn by helm:
+
+```txt
+--set defaultSettings.createDefaultDiskLabeledNodes=true
+```
+
+And then add another device formatted to Longhorn storage
+
+### Add An Extra Disk to Longhorn Storage
+
+#### Create Filesystem For The Device
+
+Create the filesystem on the device with the label `longhorn` on the storage node. Get into the node by oc command:
+
+```bash
+oc get nodes --no-headers | awk '{print $1}'
+oc debug node/${NODE_NAME} -t -- chroot /host bash
+```
+
+Check if the device is present and format it with Longhorn label:
+
+```bash
+lsblk
+sudo mkfs.ext4 -L longhorn /dev/${DEVICE_NAME}
+```
+
+#### Mounting The Device On Boot with MachineConfig CRD
+
+The secondary drive needs to be mounted automatically when node boots up by the `MachineConfig` that can be created and deployed by:
+
+```bash
+cat <<EOF >>auto-mount-machineconfig.yaml
+apiVersion: machineconfiguration.openshift.io/v1
+kind: MachineConfig
+metadata:
+  labels:
+    machineconfiguration.openshift.io/role: worker
+  name: 71-mount-storage-worker
+spec:
+  config:
+    ignition:
+      version: 3.2.0
+    systemd:
+      units:
+        - name: var-mnt-longhorn.mount
+          enabled: true
+          contents: |
+            [Unit]
+            Before=local-fs.target
+            [Mount]
+            # Example mount point, you can change it to where you like for each device.
+            Where=/var/mnt/longhorn
+            What=/dev/disk/by-label/longhorn
+            Options=rw,relatime,discard
+            [Install]
+            WantedBy=local-fs.target
+EOF
+
+oc apply -f auto-mount-machineconfig.yaml
+```
+
+#### Label and Annotate The Node
+
+Please refer to the section [Customizing Default Disks for New Nodes](../../../advanced-resources/default-disk-and-node-config/#customizing-default-disks-for-new-nodes) to label and annotate storage node on where your device is by oc commands:
+
+```bash
+oc get nodes --no-headers | awk '{print $1}'
+
+oc annotate node ${NODE_NAME} --overwrite node.longhorn.io/default-disks-config='[{"path":"/var/mnt/longhorn","allowScheduling":true}]'
+oc label node ${NODE_NAME} --overwrite node.longhorn.io/create-default-disk=config
+```
+
+**Note**: You might need to reboot the node to validate the modified configuration.
+
+## Reference
+
+- [OCP/OKD Documentation and Helm Support](https://github.com/longhorn/longhorn/pull/5004)
+- [OKD Official Website](https://www.okd.io/)
+- [OKD Official Documentation Website](https://docs.okd.io/latest/welcome/index.html)
+- [oauth-proxy](https://github.com/openshift/oauth-proxy/blob/master/contrib/sidecar.yaml)
+
+## Main Contributor
+
+- [@ArthurVardevanyan](https://github.com/ArthurVardevanyan)

content/docs/1.6.0/deploy/install/_index.md

@@ -45,6 +45,7 @@ For the minimum recommended hardware, refer to the [best practices guide.](../..
 - **Google Kubernetes Engine (GKE)** requires some additional setup for Longhorn to function properly. If you're a GKE user, refer to [this section](../../advanced-resources/os-distro-specific/csi-on-gke) for details.
 - **K3s clusters** require some extra setup. Refer to [this section](../../advanced-resources/os-distro-specific/csi-on-k3s)
 - **RKE clusters with CoreOS** need [this configuration.](../../advanced-resources/os-distro-specific/csi-on-rke-and-coreos)
+- **OCP/OKD clusters** require some extra setup. Refer to [this section](../../advanced-resources/os-distro-specific/okd-support)
 
 ### Using the Environment Check Script
 
@@ -250,5 +251,3 @@ Server Version: version.Info{Major:"1", Minor:"21", GitVersion:"v1.21.0+k3s1", G
 ```
 
 The `Server Version` should be >= v1.21.
-
-