resize raspberry pi .img file

resize-image.sh

#!/bin/bash
set -euo pipefail

usage() {
  cat <<EOF
Usage:
  $0 <image-file> [new-size] [partition-number]

Arguments:
  image-file         Path to the disk image
  new-size           New image size for qemu-img resize (default: 64G)
  partition-number   Partition to grow and resize filesystem on (default: 2)

Examples:
  $0 ~/pi-qemu-test/raspi_4_trixie.img
  $0 ~/pi-qemu-test/raspi_4_trixie.img 64G
  $0 ~/pi-qemu-test/raspi_4_trixie.img 64G 2
EOF
  exit 1
}

if [ $# -lt 1 ] || [ $# -gt 3 ]; then
  usage
fi

IMG=$(realpath "$1")
NEWSIZE="${2:-64G}"
PARTNUM="${3:-2}"

if [ ! -f "$IMG" ]; then
  echo "Error: image file not found: $IMG" >&2
  exit 1
fi

if ! [[ "$PARTNUM" =~ ^[0-9]+$ ]]; then
  echo "Error: partition number must be a positive integer" >&2
  exit 1
fi

echo "==> Image:      $IMG"
echo "==> New size:   $NEWSIZE"
echo "==> Partition:  $PARTNUM"

echo "==> Expanding image file..."
qemu-img resize -f raw "$IMG" "$NEWSIZE"

echo "==> Running Linux container to resize partition and filesystem..."
docker run --rm --privileged \
  -v "$IMG:/img/disk.img" \
  -e PARTNUM="$PARTNUM" \
  debian:latest bash -c '
set -euo pipefail

LOOP=""
cleanup() {
  set +e
  if [ -n "${LOOP:-}" ]; then
    echo "==> Cleaning up device mappings..."
    kpartx -dv "$LOOP" >/dev/null 2>&1 || true
    losetup -d "$LOOP" >/dev/null 2>&1 || true
  fi
}
trap cleanup EXIT

cat >/usr/sbin/policy-rc.d <<EOF
#!/bin/sh
exit 101
EOF
chmod +x /usr/sbin/policy-rc.d

export DEBIAN_FRONTEND=noninteractive
if ! apt-get update -qq >/tmp/apt.log 2>&1; then
  echo "apt-get update failed:" >&2
  cat /tmp/apt.log >&2
  exit 1
fi

if ! apt-get -y -qq \
  -o Dpkg::Progress-Fancy="0" \
  -o APT::Color="0" \
  -o Dpkg::Use-Pty="0" \
  --no-install-recommends \
  install \
  parted e2fsprogs kpartx util-linux xfsprogs btrfs-progs \
  >/tmp/apt-install.log 2>&1; then
  echo "apt-get install failed:" >&2
  cat /tmp/apt-install.log >&2
  exit 1
fi

echo "==> Expanding partition ${PARTNUM}..."
parted -s /img/disk.img resizepart "${PARTNUM}" 100%

echo "==> Setting up loop device..."
LOOP=$(losetup -f --show /img/disk.img)
echo "    Using $LOOP"

echo "==> Creating partition mappings..."
kpartx -av "$LOOP" >/dev/null

LOOPNAME=$(basename "$LOOP")
PART="/dev/mapper/${LOOPNAME}p${PARTNUM}"
echo "    Partition at $PART"

for _ in 1 2 3 4 5; do
  [ -b "$PART" ] && break
  sleep 1
done

if [ ! -b "$PART" ]; then
  echo "Error: partition device not found: $PART" >&2
  exit 1
fi

FSTYPE=$(blkid -o value -s TYPE "$PART" || true)
if [[ "$FSTYPE" != ext2 && "$FSTYPE" != ext3 && "$FSTYPE" != ext4 ]]; then
  echo "Error: unsupported filesystem type on $PART: ${FSTYPE:-unknown}" >&2
  exit 1
fi

echo "==> Checking filesystem..."
e2fsck -fy "$PART"

echo "==> Resizing filesystem..."
resize2fs "$PART"

echo "==> Done."
'