A script automating RPi image modifications

rpi_img_mod.sh

#!/bin/bash

# Check we are running as root!
if [ $EUID -ne 0 ]
then
    echo "Run me as root please :P"
    exit -1
fi

# Check we only received one argument!
if [ $# -ne 2 ]
then
    printf "Usage: %s <image_file> <mountpoint>\n" $0
    exit -1
fi

# Check if the file exists
if [ ! -e $1 ]
then
    echo "Couldn't find the image at $1. Quitting..."
    exit -1
fi

# Check the mountpoint exists
if [ ! -d $2 ]
then
    echo "Couldn't find the mountpoint at $2. Quitting..."
    exit -1
fi

printf "Analyzing image on file %s\n" $1

# Get the sector size and partition offsets
sector_size=$(fdisk -l $1 | head -n 2 | tail -n 1 | awk '{print $8}')
boot_offset=$(fdisk -l $1 | tail -n 2 | head -n 1 | awk '{print $2}')
rootfs_offset=$(fdisk -l $1 | tail -n 1 | awk '{print $2}')

printf "Detected sector data:\n\tSector Size   -> %8d bytes\n\tBoot Offset   -> %8d sectors\n\tRootfs Offset -> %8d sectors\n"\
        $sector_size $boot_offset $rootfs_offset

# Mount the boot partition
printf "Mounting the boot partition...\n"
mount -t vfat -o loop,offset=$(($sector_size * $boot_offset)) $1 $2

# Enable SSH headlessly
printf "Touching the ssh file to headlessly enable SSH...\n"
touch $2/ssh

# Sync the changes and unmount the boot partition
printf "Syncing changes and unmounting the boot partition...\n"
sleep 2
sync && sudo umount $2

printf "Finished modifying the image! Ready to burn :P\n"

exit 0