[WIP] Cloud Hypervisor Network Boot Image

.gitignore

kernel.img
initrd.img
rootfs.squashfs

make_boot_image.bash

#!/bin/bash

# shellcheck disable=SC2086
: ${IMAGE_FILE:='/tmp/boot.img'}

# shellcheck disable=SC2086
: ${IMAGE_SIZE:='512M'}

# shellcheck disable=SC2086
: ${MOUNT_DIR:='/mnt'}

set -eux

# Unmount EFI System Partition
if grep -qs "\s${MOUNT_DIR}\s" "/proc/mounts"; then
  umount "${MOUNT_DIR}"
fi

# Unmount Loopback Device
if losetup -lnO NAME,BACK-FILE | grep -qs "${IMAGE_FILE}"; then
  losetup -d "$(losetup -nlO NAME,BACK-FILE | grep "${IMAGE_FILE}" | awk '{print $1}')"
fi

# Remove Old Disk Image
if [ -f "${IMAGE_FILE}" ]; then
  rm "${IMAGE_FILE}"
fi

# Check Kernel Image File
if [ ! -f "kernel.img" ]; then
  echo "Require kernel.img file"
  exit 1
fi

# Check Initrd Image File
if [ ! -f "initrd.img" ]; then
  echo "Require initrd.img file"
  exit 1
fi

# Check Rootfs Image File
if [ ! -f "rootfs.squashfs" ]; then
  echo "Require rootfs.squashfs file"
  exit 1
fi

# Create Mount Directory
mkdir -p "${MOUNT_DIR}"

# Create RAW Disk Image
fallocate -l "${IMAGE_SIZE}" "${IMAGE_FILE}"

# Mount Loopback Device
LOOP_DEVICE="$(losetup --show -f -P "${IMAGE_FILE}")"

# Clear Partition Table
sgdisk -Z "${LOOP_DEVICE}"

# Create GPT Partition Table
sgdisk -o "${LOOP_DEVICE}"

# Create EFI Partition
sgdisk -n 1::-1 -c 1:EFI -t 1:ef00 "${LOOP_DEVICE}"

# Format EFI System Partition
mkfs.vfat -F 32 -n "ESP" "${LOOP_DEVICE}p1"

# Mount EFI System Partition
mount "${LOOP_DEVICE}p1" "${MOUNT_DIR}"

# Create Boot Loader Specification Directory
mkdir -p "${MOUNT_DIR}/loader/entries"

# Create Boot Loader Specification Loader File
cat > "${MOUNT_DIR}/loader/loader.conf" << __EOF__
default       linux
timeout       0
editor        no
auto-entries  0
auto-firmware 0
console-mode  auto
__EOF__

# Create Boot Loader Specification Entry File
cat > "${MOUNT_DIR}/loader/entries/linux.conf" << __EOF__
title Linux
linux /boot/kernel.img
initrd /boot/initrd.img
options console=ttyS0 root=file:///boot/rootfs.squashfs overlayroot=tmpfs quiet ---
__EOF__

# Create Boot Image Directory
mkdir "${MOUNT_DIR}/boot"

# Copy Boot Image Files
cp "kernel.img" "${MOUNT_DIR}/boot/kernel.img"
cp "initrd.img" "${MOUNT_DIR}/boot/initrd.img"
cp "rootfs.squashfs" "${MOUNT_DIR}/boot/rootfs.squashfs"

# Unmount EFI System Partition
umount "${LOOP_DEVICE}p1"

# Unmount Loopback Device
losetup -d "${LOOP_DEVICE}"