#!/bin/bash
#
# optimage.sh <foo.img>
#
# repackages filesystem images for improved compression
# all modifications to the images are non-destructive
# method shown from and explained by [mbm]
#
# created by CEnnis91 (2012)
#


if [ $(whoami) != "root" ]; then
    echo "Error: You must run as root!"
    exit 1
fi

fsimg=$(readlink -f "$1")

if [ ! -f "$fsimg" ]; then
    echo "Error: File does not exist!"
    exit 1
fi

fstype=$(file "$fsimg" | grep -io "ext[2-4]")

if [ -z "$fstype" ]; then
    echo "Error: Invalid file type!"
    exit 1
fi


fsname=$(basename "$fsimg" | sed 's|^\(.*\)[.].*$|\1|')
blkcount=$(tune2fs -l "$fsimg" | grep "Block count" | sed 's|[^0-9]*\(.*\)|\1|')
blksize=$(tune2fs -l "$fsimg" | grep "Block size" | sed 's|[^0-9]*\(.*\)|\1|')
tmpdir=$(mktemp -d)
tmplog=$(mktemp)

exec 3>&1 > $tmplog 2>&1
trap "rm -r $tmpdir" 0 1 2 3 15
trap "echo 'Something went wrong! Read $tmplog for details.' >&3; exit 0" ERR

echo "Creating blank image..." >&3
mv "$fsimg" "$fsimg.old"
dd if=/dev/zero of="$fsimg" bs=$blksize count=$blkcount
mke2fs -F -b $blksize -T "$fstype" "$fsimg"

mkdir -p "$tmpdir/$fsname" "$tmpdir/old_$fsname"

echo "Copying data over..." >&3
mount -o loop "$fsimg" "$tmpdir/$fsname"
mount -o loop "$fsimg.old" "$tmpdir/old_$fsname"
cp -af "$tmpdir/old_$fsname"/* "$tmpdir/$fsname"

umount "$tmpdir/$fsname/"
umount "$tmpdir/old_$fsname/"

owner=$(ls -al "$fsimg.old" | cut -d " " -f 3-4 | sed 's/ /:/g')
chown "$owner" "$fsimg"

echo "Success!" >&3