This simple script will mount a raspberry pi image on your computer so you can mess with it.

raspi_mount.sh

#!/bin/bash

headstart=$(sudo fdisk -l $1 | grep img2 |  awk -F" "  '{ print $2 }')

echo $headstart

if [ -z ${2+x} ]; then
    mountpoint='/mnt/raspberry'
else
    mountpoint=$2
fi

sudo mkdir $mountpoint
sudo mount -v -o offset=$(expr 512 \* $headstart) -t ext4 $1 $mountpoint