From 6dce849f97d32370f0ea0810f35f9dc7b1213884 Mon Sep 17 00:00:00 2001
From: Marco van Zijl <marco@mvzijl.nl>
Date: Sun, 4 May 2025 11:49:07 +0200
Subject: [PATCH] Update README with additional disk preparation commands for
 Ceph

---
 readme.md | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/readme.md b/readme.md
index a0be16a..6ada6dc 100644
--- a/readme.md
+++ b/readme.md
@@ -189,11 +189,26 @@ kubectl run -it --rm \
     --overrides='{"spec": { "nodeSelector": {"kubernetes.io/hostname": "master3"}}}' fix
 ```
 
-Then run the following commands:
+Search for the correct disk with `blkid`, set `DISK=/dev/sdX`, then run (some of) the following commands:
 
 ```bash
 ceph-volume lvm zap /dev/sdX --destroy
 wipefs -a /dev/sdX
+# Zap the disk to a fresh, usable state (zap-all is important, b/c MBR has to be clean)
+sgdisk --zap-all $DISK
+
+# Wipe portions of the disk to remove more LVM metadata that may be present
+dd if=/dev/zero of="$DISK" bs=1K count=200 oflag=direct,dsync seek=0 # Clear at offset 0
+dd if=/dev/zero of="$DISK" bs=1K count=200 oflag=direct,dsync seek=$((1 * 1024**2)) # Clear at offset 1GB
+dd if=/dev/zero of="$DISK" bs=1K count=200 oflag=direct,dsync seek=$((10 * 1024**2)) # Clear at offset 10GB
+dd if=/dev/zero of="$DISK" bs=1K count=200 oflag=direct,dsync seek=$((100 * 1024**2)) # Clear at offset 100GB
+dd if=/dev/zero of="$DISK" bs=1K count=200 oflag=direct,dsync seek=$((1000 * 1024**2)) # Clear at offset 1000GB
+
+# SSDs may be better cleaned with blkdiscard instead of dd
+blkdiscard $DISK
+
+# Inform the OS of partition table changes
+partprobe $DISK
 ```
 
 ### Certificate lifetimes