#!/bin/bash
#Copyright 2002 William Stearns <wstearns@pobox.com>
#Based on work by Jeff Dike <jdike@karaya.com>
#GPL'd.
VERSION='0.3.3'
MAXINT=$[ 127 * 256 * 256 * 256 ]

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 dos \(equivalent to fat and vfat\), ext2, ext3, 
	echo minix, reiser, or swap 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 "$1" in
	[Dd][Oo][Ss]|[Dd][Oo][Ss][Ff][Ss]|[Ff][Aa][Tt]|[Ff][Aa][Tt][Ff][Ss]|[Vv][Ff][Aa][Tt]|[Vv][Ff][Aa][Tt][Ff][Ss])
		FSTYPE='dos' ;		UTIL='mkdosfs' ;	MINSIZE=0 ;	MAXSIZE=2047		;;
	[Ee][Xx][Tt]2|[Ee][Xx][Tt]2[Ff][Ss])
		FSTYPE='ext2' ;		UTIL='mke2fs' ;		MINSIZE=0 ;	MAXSIZE=$MAXINT		;;
	[Ee][Xx][Tt]3|[Ee][Xx][Tt]3[Ff][Ss])
		FSTYPE='ext3' ;		UTIL='mke2fs' ;		MINSIZE=0 ;	MAXSIZE=$MAXINT		;;
	[Mm][Ii][Nn][Ii][Xx]|[Mm][Ii][Nn][Ii][Xx][Ff][Ss])
		FSTYPE='minix' ;	UTIL='mkfs.minix' ;	MINSIZE=1 ;	MAXSIZE=64		;;
	[Rr][EeIi][IiEe][Ss][Ee][Rr]|[Rr][EeIi][IiEe][Ss][Ee][Rr][Ff][Ss])
		FSTYPE='reiser' ;	UTIL='mkreiserfs' ;	MINSIZE=40 ;	MAXSIZE=2047		;;
	[Ss][Ww][Aa][Pp]|[Ss][Ww][Aa][Pp][Ff][Ss])
		FSTYPE='swap' ;		UTIL='mkswap' ;		MINSIZE=0 ;	MAXSIZE=2047		;;
	-[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=${EMPTYMEGS:-1024}
if [ -z "$FSTYPE" ]; then
	FSTYPE='ext2'
	MINSIZE=0
	MAXSIZE=$MAXINT
fi
UTIL=${UTIL:-mke2fs}

if ! type -path $UTIL >/dev/null 2>/dev/null ; then
	echo Missing utility $UTIL. Please install it. >>/dev/stderr
	exit 1
fi
if [ $EMPTYMEGS -lt $MINSIZE ]; then
	echo $FSTYPE filesystems need to be at least $MINSIZE megabytes, exiting.
	exit 1
fi
if [ $EMPTYMEGS -gt $MAXSIZE ]; then
	echo $FSTYPE filesystems can\'t be larger than $MAXSIZE megabytes, exiting.
	exit 1
fi

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" "$EMPTYFILE.old" ;		fi
fi
if [ "$FSTYPE" != "dos" ]; then
	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
fi

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

case $FSTYPE in
dos)
	#Each fat fs block is 1024 bytes
	mkdosfs -C "$EMPTYFILE" $[ $EMPTYMEGS * 1024 ] || exit 1
	chmod -x "$EMPTYFILE"
	;;
ext2)
	mke2fs -m 2 -F "$EMPTYFILE" || exit 1
	;;
ext3)
	mke2fs -j -m 2 -F "$EMPTYFILE" || exit 1
	;;
minix)
	mkfs.minix "$EMPTYFILE" || exit 1
	;;
reiser)
	#3.x.0j in rh73 does _not_ honor the -f and leaves the empty file as it is.
	#3.6.4 in rh9 _does_ honor the -f flag.
	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
	$SUDO losetup -d /dev/loop0
	;;
swap)
	mkswap "$EMPTYFILE" || exit 1
	;;
esac

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