HackingGate/expand_rootfs.sh

## expand_rootfs.sh
#!/bin/sh

# =============================================================================
# OpenWrt Root Filesystem Expander
#
# This script automates resizing the main data partition and filesystem
# on an OpenWrt device to use all available eMMC/SD card space.
#
# It now auto-detects the correct start sector and the correct device
# to target for filesystem resizing (e.g., /dev/loop0).
#
# USAGE:
# 1. Run the script: ./expand_rootfs.sh
# 2. Reboot the device when prompted.
# 3. Run the SAME script again after rebooting to resize the filesystem.
#
# =============================================================================

# --- Configuration ---
# The target disk device. On NanoPi R6S, this is typically mmcblk1.
DEVICE="/dev/mmcblk1"
# The partition number to expand. This is almost always the 2nd partition.
PARTITION_NUM="2"
# The full partition device path.
PARTITION_DEVICE="${DEVICE}p${PARTITION_NUM}"

# CLI flags
DEBUG=0
USE_PARTED=0
while [ "$#" -gt 0 ]; do
    case "$1" in
        -v|--debug)
            DEBUG=1; shift;;
        -p|--parted)
            USE_PARTED=1; shift;;
        --)
            shift; break;;
        -*)
            echo "Unknown option: $1"; exit 1;;
        *)
            break;;
    esac
done

# Helpers for logging
log() {
    echo "$@"
}

debug() {
    [ "$DEBUG" -eq 1 ] && echo "[DEBUG] $@"
}

# Run a command verbosely when DEBUG=1
run_if_available() {
    # $1: command name, rest: args
    cmd="$1"; shift
    if command -v "$cmd" >/dev/null 2>&1; then
        if [ "$DEBUG" -eq 1 ]; then
            echo "[DEBUG] $cmd $*"
        fi
        "$cmd" "$@"
        return $?
    fi
    return 127
}


# --- Functions ---
check_filesystem_size() {
    # Get the size of the overlay filesystem in KB
    df_output=$(df -k /overlay | tail -n 1)
    fs_size_kb=$(echo "$df_output" | awk '{print $2}')
    debug "df -k /overlay => $df_output (size_kb=$fs_size_kb)"

    # If filesystem is larger than 1GB (1048576 KB), we assume it's already expanded.
    if [ "$fs_size_kb" -gt 1048576 ]; then
        echo "✅ Filesystem is already expanded to $(echo "$df_output" | awk '{print int($2/1024/1024)}') GB. No action needed."
        exit 0
    fi
}

resize_partition_table() {
    echo "============================= WARNING =================================="
    echo "This script will modify the partition table on ${DEVICE}."
    echo "It will delete partition #${PARTITION_NUM} and recreate it with the maximum"
    echo "available size, using the auto-detected start sector (${START_SECTOR})."
    echo ""
    echo "This is a potentially dangerous operation. Please ensure you have"
    echo "backed up your configuration."
    echo "========================================================================"
    printf "Do you want to continue? (yes/no): "
    read -r confirmation

    if [ "$confirmation" != "yes" ]; then
        echo "Aborted by user."
        exit 1
    fi

    echo "▶️  Proceeding with fdisk..."

    if [ "$DEBUG" -eq 1 ]; then
        echo "[DEBUG] Current partition table before change (fdisk -l $DEVICE):"
        fdisk -l "$DEVICE" 2>&1 | sed 's/^/[DEBUG] /'
    fi

    # Use a "here document" to feed commands directly to fdisk
    fdisk_output=$(mktemp 2>/dev/null || echo "/tmp/fdisk.out.$$")
    fdisk "$DEVICE" <<EOF >"$fdisk_output" 2>&1
d
$PARTITION_NUM
n
p
$PARTITION_NUM
$START_SECTOR

N
w
EOF
    fdisk_rc=$?
    if [ "$DEBUG" -eq 1 ]; then
        echo "[DEBUG] fdisk scripted session output:"
        sed 's/^/[DEBUG] /' "$fdisk_output"
    fi
    rm -f "$fdisk_output" 2>/dev/null

    if [ $fdisk_rc -eq 0 ]; then
        echo "✅ Partition table successfully rewritten."
        if [ "$DEBUG" -eq 1 ]; then
            echo "[DEBUG] Partition table after change (fdisk -l $DEVICE):"
            fdisk -l "$DEVICE" 2>&1 | sed 's/^/[DEBUG] /'
            run_if_available partx -l "$DEVICE" 2>/dev/null | sed 's/^/[DEBUG] /' || true
        fi
        echo "A reboot is required for the system to see the new partition size."
        echo ""
        echo "➡️  Please run 'reboot' now, then run this script again after the"
        echo "   device comes back online to complete the process."
    else
        echo "❌ ERROR: fdisk failed to rewrite the partition table."
        exit 1
    fi
}

resize_partition_with_parted() {
    echo "▶️  Proceeding with parted to resize partition ${PARTITION_NUM} on ${DEVICE}..."
    if ! command -v parted >/dev/null 2>&1; then
        echo "❌ ERROR: 'parted' not found. Install it with: opkg update && opkg install parted"
        exit 1
    fi

    echo "[INFO] Running: parted -f -s ${DEVICE} resizepart ${PARTITION_NUM} 100%"
    parted -f -s "$DEVICE" resizepart "$PARTITION_NUM" 100%
    if [ $? -ne 0 ]; then
        echo "❌ ERROR: parted failed to resize partition."
        exit 1
    fi

    echo "✅ parted resized the partition. A reboot is recommended to ensure the kernel rereads the partition table."
    echo "➡️  Please run 'reboot' now, then run this script again after the device comes back online to complete the process."
}

resize_the_filesystem() {
    echo "▶️  Detecting device mounted at /overlay..."
    # Get the device mounted at /overlay (e.g., /dev/loop0 or /dev/mmcblk1p2)
    OVERLAY_DEVICE=$(df /overlay | tail -n 1 | awk '{print $1}')
    debug "df /overlay device => ${OVERLAY_DEVICE}"
    if [ "$DEBUG" -eq 1 ]; then
        run_if_available lsblk -f 2>/dev/null | sed 's/^/[DEBUG] /' || true
        run_if_available losetup -l 2>/dev/null | sed 's/^/[DEBUG] /' || true
        run_if_available losetup -j "$OVERLAY_DEVICE" 2>/dev/null | sed 's/^/[DEBUG] /' || true
        run_if_available block info 2>/dev/null | sed 's/^/[DEBUG] /' || true
        echo "[DEBUG] mount entries for overlay:"
        grep -E "/overlay|overlayfs" /proc/mounts | sed 's/^/[DEBUG] /' || true
    fi

    # Check if overlay is mounted on a loop device
    RESIZE_CMD=""
    RESIZE_TARGET=""

    if echo "$OVERLAY_DEVICE" | grep -q "^/dev/loop"; then
        LOOP_DEV="$OVERLAY_DEVICE"
        echo "▶️  Overlay is mounted on loop device: ${LOOP_DEV}"
        # Prefer resizing the loop device filesystem (the writable area inside squashfs)
        LOOP_FSTYPE=$(lsblk -no FSTYPE "$LOOP_DEV" 2>/dev/null || echo "")
        debug "Loop device fs type: ${LOOP_FSTYPE}"
        if [ "${LOOP_FSTYPE}" = "f2fs" ]; then
            RESIZE_CMD="resize.f2fs"
            RESIZE_TARGET="${LOOP_DEV}"
        elif [ "${LOOP_FSTYPE}" = "ext4" ]; then
            RESIZE_CMD="resize2fs"
            RESIZE_TARGET="${LOOP_DEV}"
        else
            # Unknown fs on loop device; fall back to inspecting the partition
            echo "▶️  Unknown loop fs type ('${LOOP_FSTYPE}'), falling back to partition ${PARTITION_DEVICE}"
            RESIZE_TARGET="${PARTITION_DEVICE}"
            PART_FSTYPE=$(lsblk -no FSTYPE "$PARTITION_DEVICE" 2>/dev/null || echo "")
            if [ "${PART_FSTYPE}" = "f2fs" ]; then
                RESIZE_CMD="resize.f2fs"
            else
                RESIZE_CMD="resize2fs"
            fi
        fi
    else
        echo "▶️  Overlay is mounted directly on: ${OVERLAY_DEVICE}"
        if [ -z "$OVERLAY_DEVICE" ] || ! [ -b "$OVERLAY_DEVICE" ]; then
            echo "❌ WARNING: Could not automatically detect a valid block device for /overlay."
            echo "   Attempting to fall back to the raw partition: ${PARTITION_DEVICE}"
            RESIZE_TARGET="${PARTITION_DEVICE}"
        else
            RESIZE_TARGET="${OVERLAY_DEVICE}"
        fi
        # detect fs type
        PART_FSTYPE=$(lsblk -no FSTYPE "$RESIZE_TARGET" 2>/dev/null || echo "")
        if [ "${PART_FSTYPE}" = "f2fs" ]; then
            RESIZE_CMD="resize.f2fs"
        else
            RESIZE_CMD="resize2fs"
        fi
    fi

    if [ -z "$RESIZE_CMD" ] || [ -z "$RESIZE_TARGET" ]; then
        echo "❌ ERROR: Could not determine resize command or target."
        exit 1
    fi

    if ! command -v "$RESIZE_CMD" >/dev/null 2>&1; then
        echo "❌ ERROR: Required command '$RESIZE_CMD' not found."
        if [ "$RESIZE_CMD" = "resize.f2fs" ]; then
            echo "   Install with: opkg update && opkg install f2fs-tools"
        else
            echo "   Install with: opkg update && opkg install e2fsprogs"
        fi
        exit 1
    fi

    echo "▶️  Attempting to resize the filesystem on ${RESIZE_TARGET} using ${RESIZE_CMD}..."
    debug "Invoking: ${RESIZE_CMD} ${RESIZE_TARGET}"
    ${RESIZE_CMD} "${RESIZE_TARGET}"
    rc=$?

    if [ $rc -eq 0 ]; then
        echo "✅ Filesystem resized successfully!"
        df -h /overlay
        return 0
    fi

    # If resize failed, provide targeted advice
    echo "❌ ERROR: ${RESIZE_CMD} failed (exit ${rc})."
    if [ "$RESIZE_CMD" = "resize.f2fs" ] && echo "$RESIZE_TARGET" | grep -q "^/dev/loop"; then
        echo "   The f2fs filesystem on the loop device may be in use."
        echo "   You can try forcing online resize (if supported) or run the resize from a recovery/live environment."
        echo "   Try: resize.f2fs -f ${RESIZE_TARGET}  (only if you understand the risks)"
        echo "   Or: boot a live image / initramfs, detach the loop, and run resize.f2fs on the loop device file."
    else
        echo "   Please check the device is not busy and that the correct filesystem tool is used."
    fi
    echo "[DEBUG] Helpful info:"
    run_if_available losetup -l 2>/dev/null | sed 's/^/[DEBUG] /' || true
    run_if_available lsblk -o NAME,SIZE,FSTYPE,MOUNTPOINT 2>/dev/null | sed 's/^/[DEBUG] /' || true
    exit $rc
}


# --- Main Logic ---

echo "--- OpenWrt Filesystem Expander ---"

if [ "$DEBUG" -eq 1 ]; then
    echo "[DEBUG] Script invoked with DEBUG=1"
    echo "[DEBUG] DEVICE=$DEVICE PARTITION_NUM=$PARTITION_NUM PARTITION_DEVICE=$PARTITION_DEVICE"
    run_if_available uname -a 2>/dev/null | sed 's/^/[DEBUG] /' || true
    run_if_available df -h 2>/dev/null | sed 's/^/[DEBUG] /' || true
    run_if_available lsblk 2>/dev/null | sed 's/^/[DEBUG] /' || true
fi

# Dependency Check
for cmd in fdisk resize2fs awk grep df; do
    if ! command -v $cmd >/dev/null 2>&1; then
        echo "❌ ERROR: Required command '$cmd' not found."
        case $cmd in
            fdisk) echo "   Please install 'util-linux': opkg update && opkg install util-linux";;
            resize2fs) echo "   Please install 'e2fsprogs': opkg update && opkg install e2fsprogs";;
        esac
        exit 1
    fi
done

# Check if the partition exists
if ! [ -b "$PARTITION_DEVICE" ]; then
    echo "❌ ERROR: Device ${PARTITION_DEVICE} not found."
    exit 1
fi

# Get partition info from fdisk and parse its start and end sectors
partition_info=$(fdisk -l "$DEVICE" 2>/dev/null | grep "^$PARTITION_DEVICE")
if [ -z "$partition_info" ]; then
    echo "❌ ERROR: Could not get partition info for $PARTITION_DEVICE."
    exit 1
fi
START_SECTOR=$(echo "$partition_info" | awk '{print $2}')
partition_end_sector=$(echo "$partition_info" | awk '{print $3}')
debug "Partition info line => '$partition_info'"
debug "Parsed START_SECTOR=$START_SECTOR PARTITION_END=$partition_end_sector"

# Get total disk info from fdisk and parse its end sector
disk_info=$(fdisk -l "$DEVICE" 2>/dev/null | grep "sectors$" | head -n 1)
if [ -z "$disk_info" ]; then
    echo "❌ ERROR: Could not get disk info for $DEVICE."
    exit 1
fi
disk_end_sector=$(echo "$disk_info" | awk '{print $7}')
debug "Disk info line => '$disk_info'"
debug "Parsed DISK_END=$disk_end_sector"

# Validate that the extracted values are numbers before doing math
if ! [ "$disk_end_sector" -eq "$disk_end_sector" ] 2>/dev/null || \
   ! [ "$partition_end_sector" -eq "$partition_end_sector" ] 2>/dev/null || \
   ! [ "$START_SECTOR" -eq "$START_SECTOR" ] 2>/dev/null; then
    echo "❌ ERROR: Could not parse sector counts from fdisk output."
    echo "   - Parsed Disk End Sector: '$disk_end_sector'"
    echo "   - Parsed Partition Start Sector: '$START_SECTOR'"
    echo "   - Parsed Partition End Sector: '$partition_end_sector'"
    exit 1
fi

# Stage 1: The partition is small. We need to run fdisk.
# We check if the partition's end is far from the disk's end (margin of 1000 sectors).
if [ $(($disk_end_sector - $partition_end_sector)) -gt 1000 ]; then
    echo "Phase 1: Partition table needs resizing."
    if [ "$USE_PARTED" -eq 1 ]; then
        resize_partition_with_parted
    else
        resize_partition_table
    fi
# Stage 2: The partition is large, but the filesystem might be small.
else
    echo "Phase 2: Partition table looks correct. Checking filesystem."
    check_filesystem_size
    resize_the_filesystem
fi
	#!/bin/sh

	# =============================================================================
	# OpenWrt Root Filesystem Expander
	#
	# This script automates resizing the main data partition and filesystem
	# on an OpenWrt device to use all available eMMC/SD card space.
	#
	# It now auto-detects the correct start sector and the correct device
	# to target for filesystem resizing (e.g., /dev/loop0).
	#
	# USAGE:
	# 1. Run the script: ./expand_rootfs.sh
	# 2. Reboot the device when prompted.
	# 3. Run the SAME script again after rebooting to resize the filesystem.
	#
	# =============================================================================

	# --- Configuration ---
	# The target disk device. On NanoPi R6S, this is typically mmcblk1.
	DEVICE="/dev/mmcblk1"
	# The partition number to expand. This is almost always the 2nd partition.
	PARTITION_NUM="2"
	# The full partition device path.
	PARTITION_DEVICE="${DEVICE}p${PARTITION_NUM}"

	# CLI flags
	DEBUG=0
	USE_PARTED=0
	while [ "$#" -gt 0 ]; do
	case "$1" in
	-v\|--debug)
	DEBUG=1; shift;;
	-p\|--parted)
	USE_PARTED=1; shift;;
	--)
	shift; break;;
	-*)
	echo "Unknown option: $1"; exit 1;;
	*)
	break;;
	esac
	done

	# Helpers for logging
	log() {
	echo "$@"
	}

	debug() {
	[ "$DEBUG" -eq 1 ] && echo "[DEBUG] $@"
	}

	# Run a command verbosely when DEBUG=1
	run_if_available() {
	# $1: command name, rest: args
	cmd="$1"; shift
	if command -v "$cmd" >/dev/null 2>&1; then
	if [ "$DEBUG" -eq 1 ]; then
	echo "[DEBUG] $cmd $*"
	fi
	"$cmd" "$@"
	return $?
	fi
	return 127
	}


	# --- Functions ---
	check_filesystem_size() {
	# Get the size of the overlay filesystem in KB
	df_output=$(df -k /overlay \| tail -n 1)
	fs_size_kb=$(echo "$df_output" \| awk '{print $2}')
	debug "df -k /overlay => $df_output (size_kb=$fs_size_kb)"

	# If filesystem is larger than 1GB (1048576 KB), we assume it's already expanded.
	if [ "$fs_size_kb" -gt 1048576 ]; then
	echo "✅ Filesystem is already expanded to $(echo "$df_output" \| awk '{print int($2/1024/1024)}') GB. No action needed."
	exit 0
	fi
	}

	resize_partition_table() {
	echo "============================= WARNING =================================="
	echo "This script will modify the partition table on ${DEVICE}."
	echo "It will delete partition #${PARTITION_NUM} and recreate it with the maximum"
	echo "available size, using the auto-detected start sector (${START_SECTOR})."
	echo ""
	echo "This is a potentially dangerous operation. Please ensure you have"
	echo "backed up your configuration."
	echo "========================================================================"
	printf "Do you want to continue? (yes/no): "
	read -r confirmation

	if [ "$confirmation" != "yes" ]; then
	echo "Aborted by user."
	exit 1
	fi

	echo "▶️ Proceeding with fdisk..."

	if [ "$DEBUG" -eq 1 ]; then
	echo "[DEBUG] Current partition table before change (fdisk -l $DEVICE):"
	fdisk -l "$DEVICE" 2>&1 \| sed 's/^/[DEBUG] /'
	fi

	# Use a "here document" to feed commands directly to fdisk
	fdisk_output=$(mktemp 2>/dev/null \|\| echo "/tmp/fdisk.out.$$")
	fdisk "$DEVICE" <<EOF >"$fdisk_output" 2>&1
	d
	$PARTITION_NUM
	n
	p
	$PARTITION_NUM
	$START_SECTOR

	N
	w
	EOF
	fdisk_rc=$?
	if [ "$DEBUG" -eq 1 ]; then
	echo "[DEBUG] fdisk scripted session output:"
	sed 's/^/[DEBUG] /' "$fdisk_output"
	fi
	rm -f "$fdisk_output" 2>/dev/null

	if [ $fdisk_rc -eq 0 ]; then
	echo "✅ Partition table successfully rewritten."
	if [ "$DEBUG" -eq 1 ]; then
	echo "[DEBUG] Partition table after change (fdisk -l $DEVICE):"
	fdisk -l "$DEVICE" 2>&1 \| sed 's/^/[DEBUG] /'
	run_if_available partx -l "$DEVICE" 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	fi
	echo "A reboot is required for the system to see the new partition size."
	echo ""
	echo "➡️ Please run 'reboot' now, then run this script again after the"
	echo " device comes back online to complete the process."
	else
	echo "❌ ERROR: fdisk failed to rewrite the partition table."
	exit 1
	fi
	}

	resize_partition_with_parted() {
	echo "▶️ Proceeding with parted to resize partition ${PARTITION_NUM} on ${DEVICE}..."
	if ! command -v parted >/dev/null 2>&1; then
	echo "❌ ERROR: 'parted' not found. Install it with: opkg update && opkg install parted"
	exit 1
	fi

	echo "[INFO] Running: parted -f -s ${DEVICE} resizepart ${PARTITION_NUM} 100%"
	parted -f -s "$DEVICE" resizepart "$PARTITION_NUM" 100%
	if [ $? -ne 0 ]; then
	echo "❌ ERROR: parted failed to resize partition."
	exit 1
	fi

	echo "✅ parted resized the partition. A reboot is recommended to ensure the kernel rereads the partition table."
	echo "➡️ Please run 'reboot' now, then run this script again after the device comes back online to complete the process."
	}

	resize_the_filesystem() {
	echo "▶️ Detecting device mounted at /overlay..."
	# Get the device mounted at /overlay (e.g., /dev/loop0 or /dev/mmcblk1p2)
	OVERLAY_DEVICE=$(df /overlay \| tail -n 1 \| awk '{print $1}')
	debug "df /overlay device => ${OVERLAY_DEVICE}"
	if [ "$DEBUG" -eq 1 ]; then
	run_if_available lsblk -f 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	run_if_available losetup -l 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	run_if_available losetup -j "$OVERLAY_DEVICE" 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	run_if_available block info 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	echo "[DEBUG] mount entries for overlay:"
	grep -E "/overlay\|overlayfs" /proc/mounts \| sed 's/^/[DEBUG] /' \|\| true
	fi

	# Check if overlay is mounted on a loop device
	RESIZE_CMD=""
	RESIZE_TARGET=""

	if echo "$OVERLAY_DEVICE" \| grep -q "^/dev/loop"; then
	LOOP_DEV="$OVERLAY_DEVICE"
	echo "▶️ Overlay is mounted on loop device: ${LOOP_DEV}"
	# Prefer resizing the loop device filesystem (the writable area inside squashfs)
	LOOP_FSTYPE=$(lsblk -no FSTYPE "$LOOP_DEV" 2>/dev/null \|\| echo "")
	debug "Loop device fs type: ${LOOP_FSTYPE}"
	if [ "${LOOP_FSTYPE}" = "f2fs" ]; then
	RESIZE_CMD="resize.f2fs"
	RESIZE_TARGET="${LOOP_DEV}"
	elif [ "${LOOP_FSTYPE}" = "ext4" ]; then
	RESIZE_CMD="resize2fs"
	RESIZE_TARGET="${LOOP_DEV}"
	else
	# Unknown fs on loop device; fall back to inspecting the partition
	echo "▶️ Unknown loop fs type ('${LOOP_FSTYPE}'), falling back to partition ${PARTITION_DEVICE}"
	RESIZE_TARGET="${PARTITION_DEVICE}"
	PART_FSTYPE=$(lsblk -no FSTYPE "$PARTITION_DEVICE" 2>/dev/null \|\| echo "")
	if [ "${PART_FSTYPE}" = "f2fs" ]; then
	RESIZE_CMD="resize.f2fs"
	else
	RESIZE_CMD="resize2fs"
	fi
	fi
	else
	echo "▶️ Overlay is mounted directly on: ${OVERLAY_DEVICE}"
	if [ -z "$OVERLAY_DEVICE" ] \|\| ! [ -b "$OVERLAY_DEVICE" ]; then
	echo "❌ WARNING: Could not automatically detect a valid block device for /overlay."
	echo " Attempting to fall back to the raw partition: ${PARTITION_DEVICE}"
	RESIZE_TARGET="${PARTITION_DEVICE}"
	else
	RESIZE_TARGET="${OVERLAY_DEVICE}"
	fi
	# detect fs type
	PART_FSTYPE=$(lsblk -no FSTYPE "$RESIZE_TARGET" 2>/dev/null \|\| echo "")
	if [ "${PART_FSTYPE}" = "f2fs" ]; then
	RESIZE_CMD="resize.f2fs"
	else
	RESIZE_CMD="resize2fs"
	fi
	fi

	if [ -z "$RESIZE_CMD" ] \|\| [ -z "$RESIZE_TARGET" ]; then
	echo "❌ ERROR: Could not determine resize command or target."
	exit 1
	fi

	if ! command -v "$RESIZE_CMD" >/dev/null 2>&1; then
	echo "❌ ERROR: Required command '$RESIZE_CMD' not found."
	if [ "$RESIZE_CMD" = "resize.f2fs" ]; then
	echo " Install with: opkg update && opkg install f2fs-tools"
	else
	echo " Install with: opkg update && opkg install e2fsprogs"
	fi
	exit 1
	fi

	echo "▶️ Attempting to resize the filesystem on ${RESIZE_TARGET} using ${RESIZE_CMD}..."
	debug "Invoking: ${RESIZE_CMD} ${RESIZE_TARGET}"
	${RESIZE_CMD} "${RESIZE_TARGET}"
	rc=$?

	if [ $rc -eq 0 ]; then
	echo "✅ Filesystem resized successfully!"
	df -h /overlay
	return 0
	fi

	# If resize failed, provide targeted advice
	echo "❌ ERROR: ${RESIZE_CMD} failed (exit ${rc})."
	if [ "$RESIZE_CMD" = "resize.f2fs" ] && echo "$RESIZE_TARGET" \| grep -q "^/dev/loop"; then
	echo " The f2fs filesystem on the loop device may be in use."
	echo " You can try forcing online resize (if supported) or run the resize from a recovery/live environment."
	echo " Try: resize.f2fs -f ${RESIZE_TARGET} (only if you understand the risks)"
	echo " Or: boot a live image / initramfs, detach the loop, and run resize.f2fs on the loop device file."
	else
	echo " Please check the device is not busy and that the correct filesystem tool is used."
	fi
	echo "[DEBUG] Helpful info:"
	run_if_available losetup -l 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	run_if_available lsblk -o NAME,SIZE,FSTYPE,MOUNTPOINT 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	exit $rc
	}


	# --- Main Logic ---

	echo "--- OpenWrt Filesystem Expander ---"

	if [ "$DEBUG" -eq 1 ]; then
	echo "[DEBUG] Script invoked with DEBUG=1"
	echo "[DEBUG] DEVICE=$DEVICE PARTITION_NUM=$PARTITION_NUM PARTITION_DEVICE=$PARTITION_DEVICE"
	run_if_available uname -a 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	run_if_available df -h 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	run_if_available lsblk 2>/dev/null \| sed 's/^/[DEBUG] /' \|\| true
	fi

	# Dependency Check
	for cmd in fdisk resize2fs awk grep df; do
	if ! command -v $cmd >/dev/null 2>&1; then
	echo "❌ ERROR: Required command '$cmd' not found."
	case $cmd in
	fdisk) echo " Please install 'util-linux': opkg update && opkg install util-linux";;
	resize2fs) echo " Please install 'e2fsprogs': opkg update && opkg install e2fsprogs";;
	esac
	exit 1
	fi
	done

	# Check if the partition exists
	if ! [ -b "$PARTITION_DEVICE" ]; then
	echo "❌ ERROR: Device ${PARTITION_DEVICE} not found."
	exit 1
	fi

	# Get partition info from fdisk and parse its start and end sectors
	partition_info=$(fdisk -l "$DEVICE" 2>/dev/null \| grep "^$PARTITION_DEVICE")
	if [ -z "$partition_info" ]; then
	echo "❌ ERROR: Could not get partition info for $PARTITION_DEVICE."
	exit 1
	fi
	START_SECTOR=$(echo "$partition_info" \| awk '{print $2}')
	partition_end_sector=$(echo "$partition_info" \| awk '{print $3}')
	debug "Partition info line => '$partition_info'"
	debug "Parsed START_SECTOR=$START_SECTOR PARTITION_END=$partition_end_sector"

	# Get total disk info from fdisk and parse its end sector
	disk_info=$(fdisk -l "$DEVICE" 2>/dev/null \| grep "sectors$" \| head -n 1)
	if [ -z "$disk_info" ]; then
	echo "❌ ERROR: Could not get disk info for $DEVICE."
	exit 1
	fi
	disk_end_sector=$(echo "$disk_info" \| awk '{print $7}')
	debug "Disk info line => '$disk_info'"
	debug "Parsed DISK_END=$disk_end_sector"

	# Validate that the extracted values are numbers before doing math
	if ! [ "$disk_end_sector" -eq "$disk_end_sector" ] 2>/dev/null \|\| \
	! [ "$partition_end_sector" -eq "$partition_end_sector" ] 2>/dev/null \|\| \
	! [ "$START_SECTOR" -eq "$START_SECTOR" ] 2>/dev/null; then
	echo "❌ ERROR: Could not parse sector counts from fdisk output."
	echo " - Parsed Disk End Sector: '$disk_end_sector'"
	echo " - Parsed Partition Start Sector: '$START_SECTOR'"
	echo " - Parsed Partition End Sector: '$partition_end_sector'"
	exit 1
	fi

	# Stage 1: The partition is small. We need to run fdisk.
	# We check if the partition's end is far from the disk's end (margin of 1000 sectors).
	if [ $(($disk_end_sector - $partition_end_sector)) -gt 1000 ]; then
	echo "Phase 1: Partition table needs resizing."
	if [ "$USE_PARTED" -eq 1 ]; then
	resize_partition_with_parted
	else
	resize_partition_table
	fi
	# Stage 2: The partition is large, but the filesystem might be small.
	else
	echo "Phase 2: Partition table looks correct. Checking filesystem."
	check_filesystem_size
	resize_the_filesystem
	fi
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