Shrink the size of raspberry pi image.

shrink_img.sh

#!/bin/bash

if [ $# -lt 1 ]; then
  echo -e "Shrink the size of raspberry pi image.\nUsage: bash $0 xxx.img "
  ls -l *.img
  exit
fi

IMG=$1

check_result()
{
        return_status=$?
        if [ $return_status -ne 0 ]; then
                print_log "Failed! Return Status = $return_status"
                exit 1
        else
                print_log "Done! \n"
        fi
}

print_log()
{
        echo "`date '+%F %X'`: " $1
}


print_log "Started"
sudo modprobe loop
check_result

print_log "Get loop label"
loop_label=`sudo losetup -f`
check_result
print_log "loop label: ${loop_label}"

echo "\n"

print_log "Mount image"
sudo losetup ${loop_label} ${IMG}
check_result

print_log "probe partition info: "
sudo partprobe ${loop_label}

echo "\n"

print_log "Show partition info: "
fdisk -l ${IMG}

print_log "Start gparted..."
sudo gparted ${loop_label}
check_result

# sudo losetup -D
print_log "Unmount image"
sudo losetup -d ${loop_label}
check_result

print_log "Gather info:"
block_size=`fdisk -l ${IMG} | grep 'Units: sectors' | awk -F '=' '{print $2}' | awk -F 'bytes' '{print $1}' |  xargs`
end_block=`fdisk -l ${IMG} | grep img2 | awk -F ' ' '{print $3}' |  xargs`
print_log "block_size: ${block_size}"
print_log "end_block: ${end_block}"

print_log "Trim empty space:"
truncate --size=$[(${end_block}+1)*${block_size}] ${IMG}
check_result

print_log "Compress image..."
IMG_BASENAME=`basename $IMG .img`
7za a ${IMG_BASENAME}.7z $IMG 
check_result

rm -fr $IMG