108 lines
3.4 KiB
Bash
108 lines
3.4 KiB
Bash
#!/usr/bin/env bash
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# Overwrite partition-table and ZFS vdev-label metadata at both ends of a device.
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set -euo pipefail
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readonly PASSES=10
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readonly MIB=$((1024 * 1024))
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readonly WIPE_MIB=4
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readonly WIPE_BYTES=$((WIPE_MIB * MIB))
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usage() {
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cat <<'EOF'
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Usage: sudo ./erase-zfs-metadata.sh [--source zeroes|random] /dev/<device>
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Overwrites the first and last 4 MiB of the specified block device ten times.
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This destroys MBR/GPT partition tables and all conventional ZFS vdev labels.
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The device must not be mounted or part of an imported ZFS pool.
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Options:
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--source zeroes Write zeroes from /dev/zero (default).
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--source random Write random data from /dev/urandom.
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-h, --help Show this help message.
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EOF
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}
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die() {
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printf 'Error: %s\n' "$*" >&2
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exit 1
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}
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write_source=/dev/zero
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source_name=zeroes
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device=
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while [[ $# -gt 0 ]]; do
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case $1 in
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--source)
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[[ $# -ge 2 ]] || die '--source requires zeroes or random.'
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case $2 in
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zeroes)
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write_source=/dev/zero
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source_name=zeroes
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;;
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random)
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write_source=/dev/urandom
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source_name=random
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;;
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*)
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die "invalid source '$2'; use zeroes or random."
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;;
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esac
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shift 2
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;;
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-h|--help)
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usage
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exit 0
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;;
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-*)
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die "unknown option '$1'."
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;;
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*)
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[[ -z $device ]] || die 'specify exactly one block device.'
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device=$1
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shift
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;;
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esac
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done
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[[ -n $device ]] || { usage >&2; exit 2; }
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[[ $EUID -eq 0 ]] || die 'run as root (for example, with sudo).'
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[[ -b $device ]] || die "'$device' is not a block device."
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[[ -r $write_source ]] || die "'$write_source' is not readable."
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for command in blockdev dd findmnt lsblk zpool; do
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command -v "$command" >/dev/null 2>&1 || die "required command '$command' was not found."
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done
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if findmnt --noheadings --source "$device" >/dev/null 2>&1; then
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die "'$device' is mounted; unmount it before continuing."
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fi
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if lsblk --noheadings --raw --output MOUNTPOINT "$device" | grep -q '[^[:space:]]'; then
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die "'$device' or one of its children is mounted; unmount it before continuing."
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fi
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if zpool status -P 2>/dev/null | grep -Fq -- "$device"; then
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die "'$device' belongs to an imported ZFS pool; export or detach it before continuing."
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fi
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size_bytes=$(blockdev --getsize64 "$device")
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(( size_bytes >= 2 * WIPE_BYTES )) || die "'$device' is smaller than $((2 * WIPE_MIB)) MiB."
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last_offset=$((size_bytes - WIPE_BYTES))
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printf '\nWARNING: this permanently destroys partition tables and ZFS metadata on:\n %s\nusing %s data.\n\n' "$device" "$source_name"
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lsblk --output NAME,SIZE,TYPE,MOUNTPOINTS "$device"
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read -r -p "Type exactly 'ERASE $device' to continue: " confirmation
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[[ $confirmation == "ERASE $device" ]] || die 'confirmation did not match; no data was changed.'
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for ((pass = 1; pass <= PASSES; pass++)); do
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printf 'Pass %d/%d...\n' "$pass" "$PASSES"
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dd if="$write_source" of="$device" bs="$MIB" count="$WIPE_MIB" conv=fsync,notrunc status=none
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dd if="$write_source" of="$device" bs=1 count="$WIPE_BYTES" seek="$last_offset" conv=fsync,notrunc status=none
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done
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sync
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printf 'Completed %d %s overwrite passes on %s.\n' "$PASSES" "$source_name" "$device" |