#!/bin/sh

# Copyright (C) 2007 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

set -e

TEMP=`getopt -o o:n:b:s: -n '$0' -- "$@"`

if [ $? != 0 ] ; then echo "Terminating..." >&2 ; exit 1 ; fi

# Note the quotes around `$TEMP': they are essential!
eval set -- "$TEMP"

while true; do
	case "$1" in
		-o) old_name=$2; shift 2;;

		-n) new_name=$2; shift 2;;

		-b) blockdev=$2; shift 2;;

		-s) swapdev=$2; shift 2;;

		--) shift; break;;

		*)  echo "Internal error!"; exit 1;;
	esac
done
if [ -z "$old_name" -o -z "$new_name" -o -z "$blockdev" -o -z "$swapdev" ]; then
	echo "Missing -o or -n or -b or -s argument!"
	exit 1
fi

TMPDIR=`mktemp -d` || exit 1
trap "umount $TMPDIR; rmdir $TMPDIR" EXIT

# If it's not a block device try to mount it via loopback device.
# This is needed for file disks.
MOUNT_OPTIONS=""
if [ ! -b $blockdev ]; then
  MOUNT_OPTIONS="$MOUNT_OPTIONS -o loop"
fi
mount $MOUNT_OPTIONS $blockdev $TMPDIR

HNAME="$TMPDIR/etc/hostname"
MNAME="$TMPDIR/etc/mailname"

# for hostname, we raise and error if the old hostname is not what we
# expect
OLD_HNAME="`cat $HNAME`"
if [ "$OLD_HNAME" = "$old_name" ]; then
	echo $new_name > $HNAME
else
	echo "Cannot rename from $old_name to $new_name:" 1>&2
	echo "Instance has a different hostname ($OLD_HNAME)" 1>&2
	exit 1
fi

# for mailname, we rename only if it has the old_name, otherwise we
# ignore it (and assumme that it's a customized name)
if [ "`cat $MNAME`" = "$old_name" ]; then
	echo $new_name > $MNAME
fi

umount $TMPDIR
rmdir $TMPDIR
trap - EXIT

exit 0