Add scripterase-zfs.sh which does fulla / metadata erase and verification

README.md

@@ -4,6 +4,35 @@
 a device as a ZFS vdev. It is intended for decommissioning or repurposing a
 device after it has been cleanly removed from its pool.
 
+## Unified Eraser
+
+`erase-zfs.sh` is the recommended entry point. It performs a full-device wipe
+by default and uses 10 overwrite passes. Select `--metadata` when only the
+partition tables and ZFS vdev labels should be overwritten.
+
+```bash
+chmod +x erase-zfs.sh
+sudo ./erase-zfs.sh /dev/sdX
+sudo ./erase-zfs.sh --metadata /dev/sdX
+sudo ./erase-zfs.sh --passes 3 /dev/sdX
+sudo ./erase-zfs.sh --source random --verify /dev/sdX
+```
+
+`--wipe` explicitly selects the default full-device mode. `--source zeroes`
+is the default, while `--source random` uses `/dev/urandom`. `--passes` accepts
+a positive integer and defaults to 10. `--verify` runs after wiping and checks
+`wipefs` signatures, readable ZFS labels through `zdb -l`, and ZFS pool
+discovery. A full zero wipe additionally compares every readable byte against
+`/dev/zero`. Random data cannot be byte-for-byte checked after it is written,
+so its verification is limited to the metadata and ZFS recovery checks. The
+verifier marks unavailable or ambiguous ZFS discovery as a failure rather than
+declaring the wipe successful.
+
+Pool discovery searches the target device's parent directory. Any reported
+pool may use a neighboring device, so inspect its vdev paths before treating
+the result as evidence about the erased target. A failed verification exits
+with a nonzero status and leaves all evidence in place for investigation.
+
 ## What It Erases
 
 The script performs 10 overwrite passes over the first 4 MiB and the last

erase-zfs.sh

@@ -0,0 +1,206 @@
+#!/usr/bin/env bash
+# Fully erase a device or erase its partition-table and ZFS metadata.
+
+set -euo pipefail
+
+readonly DEFAULT_PASSES=10
+readonly MIB=$((1024 * 1024))
+readonly METADATA_MIB=4
+readonly METADATA_BYTES=$((METADATA_MIB * MIB))
+
+usage() {
+    cat <<'EOF'
+Usage: sudo ./erase-zfs.sh [--wipe|--metadata] [--source zeroes|random] [--passes <count>] [--verify] /dev/<device>
+
+Fully overwrites the target device ten times by default. --metadata overwrites
+only the first and last 4 MiB, covering partition tables and ZFS vdev labels.
+
+Options:
+    --wipe            Fully overwrite the device (default).
+    --metadata        Overwrite only partition-table and ZFS metadata regions.
+    --source <value>  Write zeroes (default) or random data.
+    --passes <count>  Use a positive number of overwrite passes (default: 10).
+    --verify          Run signature, ZFS-label, and pool-discovery checks after wiping.
+    -h, --help        Show this help message.
+EOF
+}
+
+die() {
+    printf 'Error: %s\n' "$*" >&2
+    exit 1
+}
+
+wipe_mode=wipe
+write_source=/dev/zero
+source_name=zeroes
+passes=$DEFAULT_PASSES
+verify=false
+device=
+
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        --wipe)
+            wipe_mode=wipe
+            shift
+            ;;
+        --metadata)
+            wipe_mode=metadata
+            shift
+            ;;
+        --source)
+            [[ $# -ge 2 ]] || die '--source requires zeroes or random.'
+            case $2 in
+                zeroes)
+                    write_source=/dev/zero
+                    source_name=zeroes
+                    ;;
+                random)
+                    write_source=/dev/urandom
+                    source_name=random
+                    ;;
+                *) die "invalid source '$2'; use zeroes or random." ;;
+            esac
+            shift 2
+            ;;
+        --passes)
+            [[ $# -ge 2 ]] || die '--passes requires a positive integer.'
+            [[ $2 =~ ^[1-9][0-9]*$ ]] || die "invalid pass count '$2'; use a positive integer."
+            passes=$2
+            shift 2
+            ;;
+        --verify)
+            verify=true
+            shift
+            ;;
+        -h|--help)
+            usage
+            exit 0
+            ;;
+        -*) die "unknown option '$1'." ;;
+        *)
+            [[ -z $device ]] || die 'specify exactly one block device.'
+            device=$1
+            shift
+            ;;
+    esac
+done
+
+[[ -n $device ]] || { usage >&2; exit 2; }
+[[ $EUID -eq 0 ]] || die 'run as root (for example, with sudo).'
+[[ -b $device ]] || die "'$device' is not a block device."
+[[ -r $write_source ]] || die "'$write_source' is not readable."
+
+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 [[ $verify == true ]]; then
+    for command in wipefs zdb; do
+        command -v "$command" >/dev/null 2>&1 || die "--verify requires '$command'."
+    done
+    if [[ $source_name == zeroes ]]; then
+        command -v cmp >/dev/null 2>&1 || die "--verify with zeroes requires 'cmp'."
+    fi
+fi
+
+if findmnt --noheadings --source "$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 "$device")
+(( size_bytes > 0 )) || die "'$device' has no addressable capacity."
+if [[ $wipe_mode == metadata ]]; then
+    (( size_bytes >= 2 * METADATA_BYTES )) || die "'$device' is smaller than $((2 * METADATA_MIB)) MiB."
+fi
+
+printf '\nWARNING: this permanently performs a %s wipe on:\n  %s\nusing %s data for %d passes.\n\n' \
+    "$wipe_mode" "$device" "$source_name" "$passes"
+lsblk --output NAME,SIZE,TYPE,MOUNTPOINTS "$device"
+read -r -p "Type exactly 'ERASE $device' to continue: " confirmation
+[[ $confirmation == "ERASE $device" ]] || die 'confirmation did not match; no data was changed.'
+
+wipe_metadata() {
+    local last_offset=$((size_bytes - METADATA_BYTES))
+    dd if="$write_source" of="$device" bs="$MIB" count="$METADATA_MIB" iflag=fullblock conv=fsync,notrunc status=none
+    dd if="$write_source" of="$device" bs=1 count="$METADATA_BYTES" seek="$last_offset" iflag=fullblock conv=fsync,notrunc status=none
+}
+
+wipe_full_device() {
+    local whole_mib=$((size_bytes / MIB))
+    local remainder=$((size_bytes % MIB))
+
+    if (( whole_mib > 0 )); then
+        dd if="$write_source" of="$device" bs="$MIB" count="$whole_mib" iflag=fullblock conv=fsync,notrunc status=progress
+    fi
+    if (( remainder > 0 )); then
+        dd if="$write_source" of="$device" bs=1 count="$remainder" seek=$((whole_mib * MIB)) iflag=fullblock conv=fsync,notrunc status=none
+    fi
+}
+
+for ((pass = 1; pass <= passes; pass++)); do
+    printf 'Pass %d/%d...\n' "$pass" "$passes"
+    if [[ $wipe_mode == wipe ]]; then
+        wipe_full_device
+    else
+        wipe_metadata
+    fi
+done
+sync
+printf 'Completed %d %s %s passes on %s.\n' "$passes" "$source_name" "$wipe_mode" "$device"
+
+[[ $verify == true ]] || exit 0
+
+verification_failed=false
+printf '\nVerification: checking for remaining signatures.\n'
+if wipefs --all --no-act "$device"; then
+    printf 'PASS: wipefs found no signatures.\n'
+else
+    printf 'FAIL: wipefs reported one or more signatures.\n' >&2
+    verification_failed=true
+fi
+
+printf '\nVerification: checking for readable ZFS labels.\n'
+if zdb -l "$device"; then
+    printf 'FAIL: zdb found a readable ZFS label.\n' >&2
+    verification_failed=true
+else
+    printf 'PASS: zdb found no readable ZFS label.\n'
+fi
+
+printf '\nVerification: checking whether ZFS discovers an importable pool near this device.\n'
+discovery_output=
+if ! discovery_output=$(zpool import -d "$(dirname -- "$device")" 2>&1); then
+    :
+fi
+if grep -Eq '^[[:space:]]*pool:[[:space:]]' <<<"$discovery_output"; then
+    printf '%s\n' "$discovery_output"
+    printf 'FAIL: zpool found an importable pool, possibly using this device.\n' >&2
+    verification_failed=true
+elif grep -Fq 'no pools available to import' <<<"$discovery_output"; then
+    printf 'PASS: zpool found no importable pools in the device directory.\n'
+else
+    printf '%s\n' "$discovery_output" >&2
+    printf 'FAIL: zpool discovery did not produce a conclusive result.\n' >&2
+    verification_failed=true
+fi
+
+if [[ $wipe_mode == wipe && $source_name == zeroes ]]; then
+    printf '\nVerification: comparing the full device with zeroes.\n'
+    if cmp --silent /dev/zero "$device"; then
+        printf 'PASS: the complete readable device contains zeroes.\n'
+    else
+        printf 'FAIL: the complete readable device is not all zeroes.\n' >&2
+        verification_failed=true
+    fi
+fi
+
+[[ $verification_failed == false ]] || exit 1
+printf '\nVerification completed successfully.\n'