diff --git a/Debian-Jessie-Root-on-ZFS.md b/Debian-Jessie-Root-on-ZFS.md
index ef741b7..c9cc6fc 100644
--- a/Debian-Jessie-Root-on-ZFS.md
+++ b/Debian-Jessie-Root-on-ZFS.md
@@ -44,10 +44,15 @@ If you have a second system, using SSH to access the target system can be conven
 
 ## Step 2: Disk Formatting
 
-2.1  If you are re-using any disks which were previously in an MD array, zero the MD superblock now to avoid corruption if MD were to try to assemble the old array.
+2.1  If you are re-using a disk, clear it as necessary:
 
+    If the disk was previously used in an MD array, zero the superblock:
+    # apt install --yes mdadm
     # mdadm --zero-superblock --force /dev/disk/by-id/scsi-SATA_disk1
 
+    Clear the partition table:
+    # sgdisk --zap-all /dev/disk/by-id/scsi-SATA_disk1
+
 2.2  Partition your disk:
 
     Run this if you need legacy (BIOS) booting:
diff --git a/Ubuntu-16.04-Root-on-ZFS.md b/Ubuntu-16.04-Root-on-ZFS.md
index fca7e36..7b0c0e9 100644
--- a/Ubuntu-16.04-Root-on-ZFS.md
+++ b/Ubuntu-16.04-Root-on-ZFS.md
@@ -60,10 +60,11 @@ If you have a second system, using SSH to access the target system can be conven
 2.1  If you are re-using a disk, clear it as necessary:
 
     If the disk was previously used in an MD array, zero the superblock:
+    # apt install --yes mdadm
     # mdadm --zero-superblock --force /dev/disk/by-id/scsi-SATA_disk1
 
     Clear the partition table:
-    # sgdisk --zap /dev/disk/by-id/scsi-SATA_disk1
+    # sgdisk --zap-all /dev/disk/by-id/scsi-SATA_disk1
 
 2.2  Partition your disk:
 
diff --git a/Ubuntu-16.10-Root-on-ZFS.md b/Ubuntu-16.10-Root-on-ZFS.md
index 7a8bae0..35e9679 100644
--- a/Ubuntu-16.10-Root-on-ZFS.md
+++ b/Ubuntu-16.10-Root-on-ZFS.md
@@ -58,10 +58,11 @@ If you have a second system, using SSH to access the target system can be conven
 2.1  If you are re-using a disk, clear it as necessary:
 
     If the disk was previously used in an MD array, zero the superblock:
+    # apt install --yes mdadm
     # mdadm --zero-superblock --force /dev/disk/by-id/scsi-SATA_disk1
 
     Clear the partition table:
-    # sgdisk --zap /dev/disk/by-id/scsi-SATA_disk1
+    # sgdisk --zap-all /dev/disk/by-id/scsi-SATA_disk1
 
 2.2  Partition your disk: