#!/bin/bash
#Copyright 2002 William Stearns <wstearns@pobox.com>
#Based on work by Jeff Dike <jdike@karaya.com>
#GPL'd.
VERSION='0.2'

echo mkemptyfs $VERSION

usage () {
	echo Creates an empty filesystem in a file.
	echo
	echo Usage:
	echo -e '\tmkemptyfs [fstype] [size]'
	echo -e '\tmkemptyfs -h|--help'
	echo
	echo Where fstype is ext2, ext3, or reiser, and size is in megabytes.
	echo You do not need that amount of space in the current directory - 
	echo a sparse file will be created.
	echo Default is an 1024M ext2 filesystem.
}

while [ -n "$1" ]; do
	case "$1" in
	[Ee][Xx][Tt]2|[Ee][Xx][Tt]2[Ff][Ss])
		FSTYPE='ext2'
		;;
	[Ee][Xx][Tt]3|[Ee][Xx][Tt]3[Ff][Ss])
		FSTYPE='ext3'
		;;
	[Rr][EeIi][IiEe][Ss][Ee][Rr]|[Rr][EeIi][IiEe][Ss][Ee][Rr][Ff][Ss])
		FSTYPE='reiser'
		;;
	-[Hh]|--[Hh][Ee][Ll][Pp])
		usage
		exit 0
		;;
#Up to 10TB
	[0-9]|[0-9][0-9]|[0-9][0-9][0-9]|[0-9][0-9][0-9][0-9]|[0-9][0-9][0-9][0-9][0-9]|[0-9][0-9][0-9][0-9][0-9][0-9]|[0-9][0-9][0-9][0-9][0-9][0-9][0-9])
		EMPTYMEGS="$1"
		;;
	*)
		echo Unrecognized command line parameter "$1", exiting
		usage
		exit 1
		;;
	esac
	shift
done

#Defaults
EMPTYMEGS=${EMPTYMEGS:-1024}
FSTYPE=${FSTYPE:-ext2}

EMPTYFILE="emptyfs.$FSTYPE.$EMPTYMEGS"

if [ -f "$EMPTYFILE" ] || [ -f "$EMPTYFILE.old" ]; then
    echo Moving old empty filesystem out of the way...
    if [ -f "$EMPTYFILE.old" ]; then	rm -f "$EMPTYFILE.old" ;			fi
    if [ -f "$EMPTYFILE" ]; then	mv -f "$EMPTYFILE" "$EMPTYFILE.old" ;		fi
fi

echo Creating a "$EMPTYMEGS" megabyte empty "$FSTYPE" filesystem...
#Make a completely sparse file to start with
dd if=/dev/zero of="$EMPTYFILE" bs=$((1024 * 1024)) count=0 seek=$EMPTYMEGS || exit 1
#Fully filled file, no sparse usage.
#dd if=/dev/zero of="$EMPTYFILE" bs=$((1024 * 1024)) count=$EMPTYMEGS || exit 1

echo Making empty filesystem in it...
# $SUDO not necessary, it appears.

case $FSTYPE in
ext2)
	mke2fs -m 2 -F "$EMPTYFILE" || exit 1
	;;
ext3)
	mke2fs -j -m 2 -F "$EMPTYFILE" || exit 1
	;;
reiser)
	if [ $EMPTYMEGS -lt 40 ]; then
		echo Reiserfs filesystems need to be at least 40M, exiting.
		exit 1
	fi
	if [ $EMPTYMEGS -gt 2047 ]; then
		echo Reiserfs filesystems need to be loop mounted, and the loop
		echo device can\'t handle 2048M or larger files, exiting.
		exit 1
	fi
	echo Reiserfs requires a block device to build, so you either need to
	echo be root or have sudo rights to run losetup and mkreiserfs.
	if [ `whoami` = root ]; then
        	SUDO=""
	else 
	        SUDO=`which sudo`
	fi

	echo Clearing any old references to /dev/loop0
	$SUDO losetup -d /dev/loop0 || :
	echo Loopback mounting $EMPTYFILE
	$SUDO losetup /dev/loop0 "$EMPTYFILE" || exit 1
	echo Making reiserfs
	echo 'y' | $SUDO mkreiserfs /dev/loop0 || exit 1
	echo $?
	echo Clearing loop device
	$SUDO losetup -d /dev/loop0
	;;
esac

rm -f "$EMPTYFILE.bz2"
echo Compressing filesystem...
bzip2 -k -9 "$EMPTYFILE"
echo 'Done!'