Document Red Hat user namespace configurations

src/docs/self-hosted/0.5.0/install/additional-kubernetes-configs.md

@@ -0,0 +1,38 @@
+---
+url: /docs/self-hosted/0.5.0/install/additional-kubernetes-configs/
+---
+
+# Additional Kubernetes configurations
+
+While Gitpod deploys to native Kubernetes environments, several vendor-specific configurations must be made to ensure compatability with the deployment:
+* Enable User namespaces options for Kubernetes running on Red Hat Enterprise Linux
+* Grant access to `/var/gitpod` for Rancher Kubernetes custers
+
+## Enable User namespaces options for Kubernetes running on Red Hat Enterprise Linux
+
+The Docker-in-Docker image requires user namespaces to be enabled or the `image-builder` pod will fail to start with the error `OCI runtime create failed` because Red Hat Enterprise Linux (or CentOS) does not have user namespaces enabled by default. To enable user namespaces on RHEL/CentOS:
+1. Add option to kernel
+```
+grubby --args="namespace.unpriv_enable=1" --update-kernel=/boot/vmlinuz-$(uname -r)
+```
+2. Modify sysctl.conf 
+```
+echo "user.max_user_namespaces=15076" >> /etc/sysctl.conf
+```
+3. Assign users and groups to be mapped by user namespaces 
+```
+echo dockremap:808080:1000 >> /etc/subuid
+echo dockremap:808080:1000 >> /etc/subgid
+```
+4. Reboot host for changes to take effect
+
+See [Red Hat Documentation](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux_atomic_host/7/html/getting_started_with_containers/using_the_docker_command_and_service#user_namespaces_options) for more information.
+
+## Grant access to `/var/gitpod` for Rancher Kubernetes custers
+
+Rancher’s kubelet runs in a container and needs to be given explicit access to the `/var/gitpod/` path. This configuration prevents the `hostPath type check failed` error when initializing a workspace. To enable access, add the following to the cluster's `cluster.yml` manifest:
+```yaml
+    kubelet:
+      extra_binds:
+        - '/var/gitpod:/var/gitpod'
+```

src/docs/self-hosted/0.5.0/install/install-on-kubernetes.md

@@ -13,7 +13,7 @@ Gitpod also provides more optimized installations offering better performance fo
 
 ## Prerequisites
 
-- A Kubernetes Cluster in Version 1.13 or newer.
+- A Kubernetes Cluster in Version 1.13 or newer. See [additional Kubernetes configurations](../additional-kubernetes-configs/) for vendor-specific implementations.
 - [Domain](../domain)
 - [HTTPS Certificates](../https-certs): Optional, if you use an external docker registry.
 - `kubectl` with access to that cluster.