Add instructions for wiping disks for Ceph in README

readme.md

@@ -177,6 +177,25 @@ User: admin on [http://ceph.noxxos.nl](http://ceph.noxxos.nl)
 kubectl -n ceph get secret rook-ceph-dashboard-password -o jsonpath="{['data']['password']}" | base64 --decode && echo
 ```
 
+### Wiping disks for Ceph
+
+Start a temporary pod on each node where the disks are:
+
+```bash
+kubectl run -it --rm \
+    -n ceph                \
+    --image quay.io/ceph/ceph:v19.2.2       \
+    --privileged                \
+    --overrides='{"spec": { "nodeSelector": {"kubernetes.io/hostname": "master3"}}}' fix
+```
+
+Then run the following commands:
+
+```bash
+ceph-volume lvm zap /dev/sdX --destroy
+wipefs -a /dev/sdX
+```
+
 ### Certificate lifetimes
 
 Talos Linux automatically manages and rotates all server side certificates for etcd, Kubernetes, and the Talos API. Note however that the kubelet needs to be restarted at least once a year in order for the certificates to be rotated. Any upgrade/reboot of the node will suffice for this effect.