first commit

2026-09-04 16:07:18 +03:00
commit 04c5e6cf12
2 changed files with 151 additions and 0 deletions
@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+# Overwrite partition-table and ZFS vdev-label metadata at both ends of a device.
+
+set -euo pipefail
+
+readonly PASSES=10
+readonly MIB=$((1024 * 1024))
+readonly WIPE_MIB=4
+readonly WIPE_BYTES=$((WIPE_MIB * MIB))
+
+usage() {
+    cat <<'EOF'
+Usage: sudo ./erase-zfs-metadata.sh /dev/<device>
+
+Overwrites the first and last 4 MiB of the specified block device ten times.
+This destroys MBR/GPT partition tables and all conventional ZFS vdev labels.
+The device must not be mounted or part of an imported ZFS pool.
+EOF
+}
+
+die() {
+    printf 'Error: %s\n' "$*" >&2
+    exit 1
+}
+
+[[ $# -eq 1 ]] || { usage >&2; exit 2; }
+device=$1
+
+[[ $EUID -eq 0 ]] || die 'run as root (for example, with sudo).'
+[[ -b $device ]] || die "'$device' is not a block device."
+
+for command in blockdev dd findmnt lsblk zpool; do
+    command -v "$command" >/dev/null 2>&1 || die "required command '$command' was not found."
+done
+
+if findmnt --noheadings --source "$device" >/dev/null 2>&1; then
+    die "'$device' is mounted; unmount it before continuing."
+fi
+
+if lsblk --noheadings --raw --output MOUNTPOINT "$device" | grep -q '[^[:space:]]'; then
+    die "'$device' or one of its children is mounted; unmount it before continuing."
+fi
+
+if zpool status -P 2>/dev/null | grep -Fq -- "$device"; then
+    die "'$device' belongs to an imported ZFS pool; export or detach it before continuing."
+fi
+
+size_bytes=$(blockdev --getsize64 "$device")
+(( size_bytes >= 2 * WIPE_BYTES )) || die "'$device' is smaller than $((2 * WIPE_MIB)) MiB."
+
+last_offset=$((size_bytes - WIPE_BYTES))
+
+printf '\nWARNING: this permanently destroys partition tables and ZFS metadata on:\n  %s\n\n' "$device"
+lsblk --output NAME,SIZE,TYPE,MOUNTPOINTS "$device"
+read -r -p "Type exactly 'ERASE $device' to continue: " confirmation
+[[ $confirmation == "ERASE $device" ]] || die 'confirmation did not match; no data was changed.'
+
+for ((pass = 1; pass <= PASSES; pass++)); do
+    printf 'Pass %d/%d...\n' "$pass" "$PASSES"
+    dd if=/dev/zero of="$device" bs="$MIB" count="$WIPE_MIB" conv=fsync,notrunc status=none
+    dd if=/dev/zero of="$device" bs=1 count="$WIPE_BYTES" seek="$last_offset" conv=fsync,notrunc status=none
+done
+
+sync
+printf 'Completed %d overwrite passes on %s.\n' "$PASSES" "$device"