Create VMDK disk suitable for syzkaller

create-vmdk.sh

#!/bin/bash

VMDK_FILE="syzkaller.vmdk"
VMDK_SIZE="3GB"
NBD_DEV="/dev/nbd0"
NBD_DEVP1="${NBD_DEV}p1"
MOUNT_DIR="/tmp/vmdk"

ROOTFS="${1:-stretch.img}"
echo "Using ROOTFS=$ROOTFS"
KERNEL="${2:-bzImage}"
echo "Using KERNEL=$KERNEL"

[[ -e $ROOTFS ]] || {
    echo "$ROOTFS: File not found"
    exit 1
}

[[ -e $KERNEL ]] || {
    echo "$KERNEL: File not found"
    exit 1
}

# Create empty VMDK
vmware-vdiskmanager -c -s $VMDK_SIZE -t 0 -a ide "$VMDK_FILE"

# Partition the VMDK
sudo qemu-nbd -c $NBD_DEV "$VMDK_FILE"
(
echo n # Add a new partition
echo p # Primary partition
echo 1 # Partition number
echo   # First sector (Accept default)
echo   # Last sector (Accept default)
echo w # Write changes
) | sudo fdisk $NBD_DEV

# Write the root fs
sudo dd if="$ROOTFS" of=$NBD_DEVP1

# Mount the root fs
mkdir -p "$MOUNT_DIR"
sudo mount $NBD_DEVP1 "$MOUNT_DIR"

# Install bootloader
sudo grub-install --target=i386-pc --boot-directory="$MOUNT_DIR/boot" $NBD_DEV

# Install kernel
sudo cp "$KERNEL" "$MOUNT_DIR/boot/bzImage"

# Configure the bootloader
cat << EOF | sudo tee "$MOUNT_DIR/boot/grub/grub.cfg"
insmod ext2
set timeout=5

menuentry 'Syzkaller' {
    insmod ext2
    linux  /boot/bzImage root=/dev/sda1
}
EOF

# Cleanup
sudo umount $MOUNT_DIR
sudo qemu-nbd -d $NBD_DEV