core-admin/linux/aux-tools/prepare-volatile-img.sh

#!/bin/sh

if [ "`id -u`" != "0" ]; then
	exec sudo $0 $*
fi

set -e

FILENAME=$1
ROOT_SIZE=$2
SWAP_SIZE=$[ 1024 ]

if [ -z "$ROOT_SIZE" -o -z "$FILENAME" ]; then
	echo "Usage: $0 <filename> <root.img size in MB>"
	exit 1
fi

if [ -e "$FILENAME" ]; then
	echo "$FILENAME already exists, not overriding"
	exit 1
fi

# Cleanup lefovers from possible previous run
loopdev=`losetup -a | grep "$FILENAME" | cut -f 1 -d :`
if [ -n "$loopdev" ]; then
    dmsetup remove `basename $loopdev`p1 2>/dev/null
    dmsetup remove `basename $loopdev`p2 2>/dev/null
    losetup -d $loopdev
    udevadm settle
fi

TOTAL_SIZE=$[ $ROOT_SIZE + $SWAP_SIZE + 512 ]
truncate -s ${TOTAL_SIZE}M "$FILENAME"
sfdisk --no-reread -u M "$FILENAME" > /dev/null 2> /dev/null <<EOF
0,${SWAP_SIZE},S
,${ROOT_SIZE},L
EOF

kpartx -s -a "$FILENAME"
loopdev=`losetup -j "$FILENAME"|tail -n 1 |cut -d: -f1`
looppart=`echo $loopdev|sed 's:dev:dev/mapper:'`
mkswap -f ${looppart}p1 > /dev/null
udevadm settle
kpartx -s -d ${loopdev}
losetup -d ${loopdev} || :
chown --reference `dirname "$FILENAME"` "$FILENAME"