maintaining many Xen VMs

I recently brought up 3 DomUs; the result, of course, is
that I now have 3
more machines to administer.  This is known as a bad
tradeoff...  I'm
curious, though, how other people are solving this.

My (NetBSD) DomUs are going to be mostly identical.  I was
thinking of
having a shared, read-only /usr and separate /var.  I
probably need
separate roots, if only to have separate /etc/rc.conf files.
 /usr will be
a real partition, probably shared with the Dom0.  The Dom0
would also have
a separate partition that held the vnds for the DomUs.

The problem is updating pkgsrc -- compilations on the Dom0
(with the DomUs
shut down) would be slow, since I'm not allocating much
phyiscal memory to
Dom0.

Anyway -- how are other people handling this?  I thought
about NFS, but I
suspect it's too slow.

		--Steven M. Bellovin, http://www.cs.columbi
a.edu/~smb

Steven M. Bellovin wrote:
> I recently brought up 3 DomUs; the result, of course,
is that I now have 3
> more machines to administer.  This is known as a bad
tradeoff...  I'm
> curious, though, how other people are solving this.
> 
> My (NetBSD) DomUs are going to be mostly identical.  I
was thinking of
> having a shared, read-only /usr and separate /var.  I
probably need
> separate roots, if only to have separate /etc/rc.conf
files.  /usr will be
> a real partition, probably shared with the Dom0.  The
Dom0 would also have
> a separate partition that held the vnds for the DomUs.
> 
> The problem is updating pkgsrc -- compilations on the
Dom0 (with the DomUs
> shut down) would be slow, since I'm not allocating much
phyiscal memory to
> Dom0.
> 
> Anyway -- how are other people handling this?  I
thought about NFS, but I
> suspect it's too slow.

I use disk images mounted on vnd devices for my domUs.  My
domUs are 
mostly the same, so what I do is:

    1) Have one read-only root filesystem image that has a
full NetBSD
       installation (about 400Mb).

    2) Create a separate disk image for the /usr/pkg
filesystem per domU.

    3) Create a separate disk image for the /local
filesystem per domU.
       These vary in size depending on the domU and provide
local
       storage space.

    4) Null-mount /local/etc and /local/var over /etc and
/var during
       startup.

    5) Use MFS for the /dev mount.

This lets you:

    * Update the base install of NetBSD across all your
domUs at once by
      swapping in a new root.img.  This is mostly only
useful if you're
      planning on tracking a minor or teeny release, not a
major upgrade.

    * Swap out the pkg.img with one with newer packages on
it, and
      quickly swap back when stuff breaks.

    * Creatively make /local into a cgd filesystem, so only
the local
      data is encrypted while the packages and root
filesystem aren't.

There are some modifications that need to be made to /etc in
the 
root.img file and also to /local/etc in the local.img files.
 I've 
attached some quick-and-dirty scripts that I use to set up
my domUs.  I 
offer them without much explanation, so you'll have to read
through them 
to figure out what's going on.

	Cheers,

	-- Johnny Lam <jlampkgsrc.org>
#!/bin/sh

block_file=/usr/pkg/etc/xen/block-file
img=
kernel=netbsd-XENU
tmpdir=/tmp/$$

# Parse options
while [ $# -gt 0 ]; do
	case "$1" in
	-k)	kernel=$2; shift 2 ;;
	-*)	echo 1>&2 "$0: unknown option
``$1''"; exit 1 ;;
	*)	break ;;
	esac
done

if [ $# -lt 1 ]; then
	echo 1>&2 "$0: missing image file"
	exit 1
fi

img="$1"

###
### Check for necessary files before starting.
###
if [ ! -x "$block_file" ]; then
	echo 1>&2 "$0: $block_file cannot be
executed"
	exit 1
fi
if [ ! -f "$img" ]; then
	echo 1>&2 "$0: missing $img";
	exit 1
fi
if [ ! -f "$kernel" ]; then
	echo 1>&2 "$0: missing $kernel";
	exit 1
fi

###
### Mount root.img onto /mnt for manipulation.
###
echo "Mounting $img"
dev=`$block_file bind $img`
vnd="${dev#/dev/}"; vnd="${vnd%[a-z]}"
mnt=$tmpdir/mnt
mkdir -p $mnt
mount /dev/$a $mnt

###
### Put the XENU kernel into place.
###
echo "Copying XENU kernel into $img"
rm -f $mnt/netbsd
cp -f $kernel $mnt
case "$kernel" in
netbsd) ;;
*)	ln -f $mnt/$kernel $mnt/netbsd ;;
esac

###
### Prepare for MFS /dev.  Modify the "init"
target of the MAKEDEV script
### to create a few more virtual disk devices and also the
power devices.
###
echo "Preparing MFS /dev"
makedev=$mnt/dev/MAKEDEV
if [ -f $makedev ]; then
	rm -rf $mnt/dev/[a-z]*
	[ -f $makedev.orig ] || mv -f $makedev $makedev.orig
	awk '/makedev xbd0 xbd1 xencons/ {
		sub("xencons", "xbd2 xbd3 xbd4
xencons");
		print $0;
		print "	makedev sysmon";
		print "	makedev clockctl";
		print "	makedev ipl pf crypto systrace";
		print "	makedev tun0 tun1 tun2 tun3";
		print "	makedev tap tap0 tap1 tap2 tap3";
		print "	makedev kttcp";
		next;
	     }
	     /makedev st0/ {
		print "	makedev vnd0"
		next
	     }
	     /makedev iop0/ 
	     /makedev ed0/ 
	     /makedev ld0/ 
	     ' 
		$makedev.orig > $makedev
	[ ! -x $makedev.orig ] || chmod +x $makedev
fi

###
### Create directories on which we intend to mount
additional filesystems.
###	emul	emulation shadow directories
###	local	filesystem mounted on cgd(4) device	
###	usr/pkg	mount point for pkgsrc-installed software
###
echo "Populating filesystem directories"
( cd $mnt && mkdir -p emul local usr/pkg )

###
### Add hook to mount /local/etc onto /etc so that our
system-specific
### configuration is used.  We insert the hook at the start
of the rc
### script just before we source any other files.
###
echo "Creating local rc hook"
cat > $mnt/etc/rc.pre-hooks << 'EOF'
# rc.pre-hooks

# Mount /local to get the local configuration data.  We must
fsck the
# partition beforehand to ensure that it's clean because we
won't be
# able to fix any problems later on after other filesystems
are mounted.
#
/sbin/fsck -p /dev/rxbd2a
case $? in
0)	;;
*)	if [ "$1" = autoboot ]; then
		kill -TERM $$
	fi
	exit 1
	;;
esac
if ! mount -t ffs /dev/xbd2a /local; then
	echo "Unable to mount /local.  Multiuser boot
aborted."
	exit 1
fi

# Mount /etc to get the real configuration files.
if ! mount -t null /local/etc /etc; then
	echo "Unable to mount /etc.  Multiuser boot
aborted."
	exit 1
fi

# Re-exec /etc/rc so that we use the correct configuration
information,
# e.g., /etc/rc.conf settings, etc.
#
exec /bin/sh $0
EOF

rc=$mnt/etc/rc
if [ -f $rc ] && ! grep -q
"/etc/rc.pre-hooks" $rc; then
	mv -f $rc $rc.orig
	awk '/^. /etc/rc.subr$/ {
		print ". /etc/rc.pre-hooks"
	     }
	     ' 
		$rc.orig > $rc
	[ ! -x $rc.orig ] || chmod +x $rc
fi

###
### Cleanup
###
echo "Unmounting $img"
umount $mnt
rmdir $mnt
rmdir $tmpdir
$block_file unbind $dev
#!/bin/sh

block_file=/usr/pkg/etc/xen/block-file
block_cgd=/usr/pkg/etc/xen/block-cgd
img_root=
img_local=
keyfile=
tmpdir=/tmp/$$

# Parse options
while [ $# -gt 0 ]; do
	case "$1" in
	-c)	keyfile="$2"; shift 2 ;;
	-*)	echo 1>&2 "$0: unknown option
``$1''"; exit 1 ;;
	*)	break ;;
	esac
done

if [ $# -lt 2 ]; then
	echo 1>&2 "$0: missing image files"
	exit 1
fi

img_root="$1"
img_local="$2"

###
### Check for necessary files before starting.
###
if [ ! -x "$block_file" ]; then
	echo 1>&2 "$0: $block_file cannot be
executed"
	exit 1
fi
if [ -n "$keyfile" -a ! -x "$block_cgd"
]; then
	echo 1>&2 "$0: $block_cgd cannot be
executed"
	exit 1
fi

###
### Check for necessary files before starting.
###
if [ ! -f "$img_root" ]; then
	echo 1>&2 "$0: missing $img_root";
	exit 1
fi
if [ ! -f "$img_local" ]; then
	echo 1>&2 "$0: missing $img_local";
	exit 1
fi

###
### Mount root.img onto /mnt.
###
echo "Mounting $img_root"
dev_root=`$block_file bind $img_root`
vnd_root="${dev_root#/dev/}";
vnd_root="${vnd_root%[a-z]}"
mnt_root=$tmpdir/mnt
mkdir -p $mnt_root
mount -r /dev/$a $mnt_root

###
### Mount local image onto /local.
###
echo "Mounting $img_local"
dev_local=`$block_file bind $img_local`
vnd_local="${dev_local#/dev/}";
vnd_local="${vnd_local%[a-z]}"
if [ -n "$keyfile" ]; then
	dev_cgd=`$block_cgd bind /dev/$a $keyfile`
	cgd="${dev_cgd#/dev/}";
cgd="${cgd%[a-z]}"
fi

mnt_local=$tmpdir/local
mkdir -p $mnt_local
if [ -n "$keyfile" ]; then
	mount /dev/$a $mnt_local
else
	mount /dev/$a $mnt_local
fi

###
### Copy "etc", "tmp" and
"var" into place.
###
echo "Copying mutable directories from $img_root to
$img_local"
( cd $mnt_root && pax -rwpe etc tmp var $mnt_local/.
)

###
### Restore the original /etc/rc script.
###
echo "Restoring vanilla rc script"
if [ -f $mnt_local/etc/rc.orig ]; then
	rm -f $mnt_local/etc/rc.pre-hooks
	mv -f $mnt_local/etc/rc.orig $mnt_local/etc/rc
fi

###
### Add configuration bits to re-mount /local as read-write
from
### /etc/rc.d/root.
###
echo "Add bit to re-mount /local as read-write"
cat > $mnt_local/etc/rc.conf.d/root << 'EOF'
start_postcmd="root_poststart"

root_poststart()
{
	# Re-mount /local as a read-write filesystem.
	mount -uw /local
}
EOF

###
### Add additional filesystems into /local/etc/fstab.
###
echo "Add our filesystems to /etc/fstab"
fstab=$mnt_local/etc/fstab
[ -f $fstab.orig ] || mv -f $fstab $fstab.orig
cat > $fstab << 'EOF'
/dev/xbd0a / ffs rw 1 1
/dev/cgd0b none swap sw 0 0
/dev/xbd2a /local ffs rw 0 0
/dev/xbd3a /usr/pkg ffs rw 1 2
/local/etc /etc null rw
/local/tmp /tmp null rw
/local/var /var null rw
kernfs /kern kernfs rw
procfs /proc procfs rw,noauto
EOF

###
### Edit the vanilla rc.conf script to add the extra bits
for the domU setup.
###
echo "Modify rc.conf for domU setup"
rc_conf=$mnt_local/etc/rc.conf
if [ -f $rc_conf ] && ! grep -q
"critical_filesystems_local" $rc_conf; then
	mv -f $rc_conf $rc_conf.orig
	awk '/^wscons=/ {
		print "critical_filesystems_local="/local /etc
/tmp /var"";
		print "powerd=YES";
		print "savecore=NO";
		print "sendmail=NO";
		print "wscons=NO";
		next;
	     }
	     ' 
		$rc_conf.orig > $rc_conf
fi

###
### Set up encrypted swap.
###
echo "Set up encrypted swap for the domU"
cat > $mnt_local/etc/cgd/cgd.conf << 'EOF'
cgd0	/dev/xbd1a
EOF

cat > $mnt_local/etc/cgd/xbd1a << 'EOF'
algorithm blowfish-cbc;
iv-method encblkno;
keylength 128;
verify_method none;
keygen urandomkey;
EOF

cat > $mnt_local/etc/rc.conf.d/cgd << 'EOF'
swap_device="cgd0"
swap_disklabel="/etc/cgd/xbd1a.disklabel"
start_postcmd="cgd_swap"

cgd_swap()
{
	# Convert this dedicated swap device to contain one big
swap
	# partition.
	#
	disklabel $swap_device 2>/dev/null |
	while read line; do
		case "$line" in
		d)	bline=&quo
t; b:${line#d:}"
			bline="${bline%%unused*} 
swap${bline##*unused}"
			echo "$bline"
			echo "$line"
			;;
		[a-z]) ;;
		*)	echo "$line"
			;;
		esac
	done > $swap_disklabel 
	if ! disklabel -R -r $swap_device $swap_disklabel
2>/dev/null; then
		echo 1>&2 "Could not write $swap_disklabel to
$swap_device"
	fi
}
EOF

###
### Only turn on the console tty.
###
echo "Disable non-console ttys"
ttys=$mnt_local/etc/ttys
[ -f $ttys.orig ] || mv -f $ttys $ttys.orig
sed -e "/^tty/{s,on secure,off secure,;}"
$ttys.orig > $ttys

###
### Disable the daily and weekly checks in root's crontab.
###
echo "Disable daily and weekly checks in root's
crontab"
crontab=$mnt_local/var/cron/tabs/root
awk '/^[^#].*/etc/(daily|weekly)/ { print "#"
$0; next } ' 
	$crontab > $crontab.new
mv -f $crontab.new $crontab

###
### Cleanup
###
echo "Unmounting $img_root and $img_local"
umount $mnt_root
umount $mnt_local
rmdir $mnt_root
rmdir $mnt_local
rmdir $tmpdir
$block_file unbind $dev_root
[ -z "$keyfile" ] || $block_cgd unbind $dev_cgd
$block_file unbind $dev_local

Thanks.  For better or worse, we have similar philosophies
on how to solve
the problem.  It's probably worth some effort to figure out
the "right"
general solution.

Steven M. Bellovin wrote:
> I recently brought up 3 DomUs; the result, of course,
is that I now have 3
> more machines to administer.  This is known as a bad
tradeoff...  I'm
> curious, though, how other people are solving this.
> 
> My (NetBSD) DomUs are going to be mostly identical.  I
was thinking of
> having a shared, read-only /usr and separate /var.  I
probably need
> separate roots, if only to have separate /etc/rc.conf
files.  /usr will be
> a real partition, probably shared with the Dom0.  The
Dom0 would also have
> a separate partition that held the vnds for the DomUs.
> 
> The problem is updating pkgsrc -- compilations on the
Dom0 (with the DomUs
> shut down) would be slow, since I'm not allocating much
phyiscal memory to
> Dom0.
> 
> Anyway -- how are other people handling this?  I
thought about NFS, but I
> suspect it's too slow.

I use disk images mounted on vnd devices for my domUs.  My
domUs are 
mostly the same, so what I do is:

    1) Have one read-only root filesystem image that has a
full NetBSD
       installation (about 400Mb).

    2) Create a separate disk image for the /usr/pkg
filesystem per domU.

    3) Create a separate disk image for the /local
filesystem per domU.
       These vary in size depending on the domU and provide
local
       storage space.

    4) Null-mount /local/etc and /local/var over /etc and
/var during
       startup.

    5) Use MFS for the /dev mount.

This lets you:

    * Update the base install of NetBSD across all your
domUs at once by
      swapping in a new root.img.  This is mostly only
useful if you're
      planning on tracking a minor or teeny release, not a
major upgrade.

    * Swap out the pkg.img with one with newer packages on
it, and
      quickly swap back when stuff breaks.

    * Creatively make /local into a cgd filesystem, so only
the local
      data is encrypted while the packages and root
filesystem aren't.

There are some modifications that need to be made to /etc in
the 
root.img file and also to /local/etc in the local.img files.
 I've 
attached some quick-and-dirty scripts that I use to set up
my domUs.  I 
offer them without much explanation, so you'll have to read
through them 
to figure out what's going on.

	Cheers,

	-- Johnny Lam <jlampkgsrc.org>
#!/bin/sh

block_file=/usr/pkg/etc/xen/block-file
img=
kernel=netbsd-XENU
tmpdir=/tmp/$$

# Parse options
while [ $# -gt 0 ]; do
	case "$1" in
	-k)	kernel=$2; shift 2 ;;
	-*)	echo 1>&2 "$0: unknown option
``$1''"; exit 1 ;;
	*)	break ;;
	esac
done

if [ $# -lt 1 ]; then
	echo 1>&2 "$0: missing image file"
	exit 1
fi

img="$1"

###
### Check for necessary files before starting.
###
if [ ! -x "$block_file" ]; then
	echo 1>&2 "$0: $block_file cannot be
executed"
	exit 1
fi
if [ ! -f "$img" ]; then
	echo 1>&2 "$0: missing $img";
	exit 1
fi
if [ ! -f "$kernel" ]; then
	echo 1>&2 "$0: missing $kernel";
	exit 1
fi

###
### Mount root.img onto /mnt for manipulation.
###
echo "Mounting $img"
dev=`$block_file bind $img`
vnd="${dev#/dev/}"; vnd="${vnd%[a-z]}"
mnt=$tmpdir/mnt
mkdir -p $mnt
mount /dev/$a $mnt

###
### Put the XENU kernel into place.
###
echo "Copying XENU kernel into $img"
rm -f $mnt/netbsd
cp -f $kernel $mnt
case "$kernel" in
netbsd) ;;
*)	ln -f $mnt/$kernel $mnt/netbsd ;;
esac

###
### Prepare for MFS /dev.  Modify the "init"
target of the MAKEDEV script
### to create a few more virtual disk devices and also the
power devices.
###
echo "Preparing MFS /dev"
makedev=$mnt/dev/MAKEDEV
if [ -f $makedev ]; then
	rm -rf $mnt/dev/[a-z]*
	[ -f $makedev.orig ] || mv -f $makedev $makedev.orig
	awk '/makedev xbd0 xbd1 xencons/ {
		sub("xencons", "xbd2 xbd3 xbd4
xencons");
		print $0;
		print "	makedev sysmon";
		print "	makedev clockctl";
		print "	makedev ipl pf crypto systrace";
		print "	makedev tun0 tun1 tun2 tun3";
		print "	makedev tap tap0 tap1 tap2 tap3";
		print "	makedev kttcp";
		next;
	     }
	     /makedev st0/ {
		print "	makedev vnd0"
		next
	     }
	     /makedev iop0/ 
	     /makedev ed0/ 
	     /makedev ld0/ 
	     ' 
		$makedev.orig > $makedev
	[ ! -x $makedev.orig ] || chmod +x $makedev
fi

###
### Create directories on which we intend to mount
additional filesystems.
###	emul	emulation shadow directories
###	local	filesystem mounted on cgd(4) device	
###	usr/pkg	mount point for pkgsrc-installed software
###
echo "Populating filesystem directories"
( cd $mnt && mkdir -p emul local usr/pkg )

###
### Add hook to mount /local/etc onto /etc so that our
system-specific
### configuration is used.  We insert the hook at the start
of the rc
### script just before we source any other files.
###
echo "Creating local rc hook"
cat > $mnt/etc/rc.pre-hooks << 'EOF'
# rc.pre-hooks

# Mount /local to get the local configuration data.  We must
fsck the
# partition beforehand to ensure that it's clean because we
won't be
# able to fix any problems later on after other filesystems
are mounted.
#
/sbin/fsck -p /dev/rxbd2a
case $? in
0)	;;
*)	if [ "$1" = autoboot ]; then
		kill -TERM $$
	fi
	exit 1
	;;
esac
if ! mount -t ffs /dev/xbd2a /local; then
	echo "Unable to mount /local.  Multiuser boot
aborted."
	exit 1
fi

# Mount /etc to get the real configuration files.
if ! mount -t null /local/etc /etc; then
	echo "Unable to mount /etc.  Multiuser boot
aborted."
	exit 1
fi

# Re-exec /etc/rc so that we use the correct configuration
information,
# e.g., /etc/rc.conf settings, etc.
#
exec /bin/sh $0
EOF

rc=$mnt/etc/rc
if [ -f $rc ] && ! grep -q
"/etc/rc.pre-hooks" $rc; then
	mv -f $rc $rc.orig
	awk '/^. /etc/rc.subr$/ {
		print ". /etc/rc.pre-hooks"
	     }
	     ' 
		$rc.orig > $rc
	[ ! -x $rc.orig ] || chmod +x $rc
fi

###
### Cleanup
###
echo "Unmounting $img"
umount $mnt
rmdir $mnt
rmdir $tmpdir
$block_file unbind $dev
#!/bin/sh

block_file=/usr/pkg/etc/xen/block-file
block_cgd=/usr/pkg/etc/xen/block-cgd
img_root=
img_local=
keyfile=
tmpdir=/tmp/$$

# Parse options
while [ $# -gt 0 ]; do
	case "$1" in
	-c)	keyfile="$2"; shift 2 ;;
	-*)	echo 1>&2 "$0: unknown option
``$1''"; exit 1 ;;
	*)	break ;;
	esac
done

if [ $# -lt 2 ]; then
	echo 1>&2 "$0: missing image files"
	exit 1
fi

img_root="$1"
img_local="$2"

###
### Check for necessary files before starting.
###
if [ ! -x "$block_file" ]; then
	echo 1>&2 "$0: $block_file cannot be
executed"
	exit 1
fi
if [ -n "$keyfile" -a ! -x "$block_cgd"
]; then
	echo 1>&2 "$0: $block_cgd cannot be
executed"
	exit 1
fi

###
### Check for necessary files before starting.
###
if [ ! -f "$img_root" ]; then
	echo 1>&2 "$0: missing $img_root";
	exit 1
fi
if [ ! -f "$img_local" ]; then
	echo 1>&2 "$0: missing $img_local";
	exit 1
fi

###
### Mount root.img onto /mnt.
###
echo "Mounting $img_root"
dev_root=`$block_file bind $img_root`
vnd_root="${dev_root#/dev/}";
vnd_root="${vnd_root%[a-z]}"
mnt_root=$tmpdir/mnt
mkdir -p $mnt_root
mount -r /dev/$a $mnt_root

###
### Mount local image onto /local.
###
echo "Mounting $img_local"
dev_local=`$block_file bind $img_local`
vnd_local="${dev_local#/dev/}";
vnd_local="${vnd_local%[a-z]}"
if [ -n "$keyfile" ]; then
	dev_cgd=`$block_cgd bind /dev/$a $keyfile`
	cgd="${dev_cgd#/dev/}";
cgd="${cgd%[a-z]}"
fi

mnt_local=$tmpdir/local
mkdir -p $mnt_local
if [ -n "$keyfile" ]; then
	mount /dev/$a $mnt_local
else
	mount /dev/$a $mnt_local
fi

###
### Copy "etc", "tmp" and
"var" into place.
###
echo "Copying mutable directories from $img_root to
$img_local"
( cd $mnt_root && pax -rwpe etc tmp var $mnt_local/.
)

###
### Restore the original /etc/rc script.
###
echo "Restoring vanilla rc script"
if [ -f $mnt_local/etc/rc.orig ]; then
	rm -f $mnt_local/etc/rc.pre-hooks
	mv -f $mnt_local/etc/rc.orig $mnt_local/etc/rc
fi

###
### Add configuration bits to re-mount /local as read-write
from
### /etc/rc.d/root.
###
echo "Add bit to re-mount /local as read-write"
cat > $mnt_local/etc/rc.conf.d/root << 'EOF'
start_postcmd="root_poststart"

root_poststart()
{
	# Re-mount /local as a read-write filesystem.
	mount -uw /local
}
EOF

###
### Add additional filesystems into /local/etc/fstab.
###
echo "Add our filesystems to /etc/fstab"
fstab=$mnt_local/etc/fstab
[ -f $fstab.orig ] || mv -f $fstab $fstab.orig
cat > $fstab << 'EOF'
/dev/xbd0a / ffs rw 1 1
/dev/cgd0b none swap sw 0 0
/dev/xbd2a /local ffs rw 0 0
/dev/xbd3a /usr/pkg ffs rw 1 2
/local/etc /etc null rw
/local/tmp /tmp null rw
/local/var /var null rw
kernfs /kern kernfs rw
procfs /proc procfs rw,noauto
EOF

###
### Edit the vanilla rc.conf script to add the extra bits
for the domU setup.
###
echo "Modify rc.conf for domU setup"
rc_conf=$mnt_local/etc/rc.conf
if [ -f $rc_conf ] && ! grep -q
"critical_filesystems_local" $rc_conf; then
	mv -f $rc_conf $rc_conf.orig
	awk '/^wscons=/ {
		print "critical_filesystems_local="/local /etc
/tmp /var"";
		print "powerd=YES";
		print "savecore=NO";
		print "sendmail=NO";
		print "wscons=NO";
		next;
	     }
	     ' 
		$rc_conf.orig > $rc_conf
fi

###
### Set up encrypted swap.
###
echo "Set up encrypted swap for the domU"
cat > $mnt_local/etc/cgd/cgd.conf << 'EOF'
cgd0	/dev/xbd1a
EOF

cat > $mnt_local/etc/cgd/xbd1a << 'EOF'
algorithm blowfish-cbc;
iv-method encblkno;
keylength 128;
verify_method none;
keygen urandomkey;
EOF

cat > $mnt_local/etc/rc.conf.d/cgd << 'EOF'
swap_device="cgd0"
swap_disklabel="/etc/cgd/xbd1a.disklabel"
start_postcmd="cgd_swap"

cgd_swap()
{
	# Convert this dedicated swap device to contain one big
swap
	# partition.
	#
	disklabel $swap_device 2>/dev/null |
	while read line; do
		case "$line" in
		d)	bline=&quo
t; b:${line#d:}"
			bline="${bline%%unused*} 
swap${bline##*unused}"
			echo "$bline"
			echo "$line"
			;;
		[a-z]) ;;
		*)	echo "$line"
			;;
		esac
	done > $swap_disklabel 
	if ! disklabel -R -r $swap_device $swap_disklabel
2>/dev/null; then
		echo 1>&2 "Could not write $swap_disklabel to
$swap_device"
	fi
}
EOF

###
### Only turn on the console tty.
###
echo "Disable non-console ttys"
ttys=$mnt_local/etc/ttys
[ -f $ttys.orig ] || mv -f $ttys $ttys.orig
sed -e "/^tty/{s,on secure,off secure,;}"
$ttys.orig > $ttys

###
### Disable the daily and weekly checks in root's crontab.
###
echo "Disable daily and weekly checks in root's
crontab"
crontab=$mnt_local/var/cron/tabs/root
awk '/^[^#].*/etc/(daily|weekly)/ { print "#"
$0; next } ' 
	$crontab > $crontab.new
mv -f $crontab.new $crontab

###
### Cleanup
###
echo "Unmounting $img_root and $img_local"
umount $mnt_root
umount $mnt_local
rmdir $mnt_root
rmdir $mnt_local
rmdir $tmpdir
$block_file unbind $dev_root
[ -z "$keyfile" ] || $block_cgd unbind $dev_cgd
$block_file unbind $dev_local

Thanks.  For better or worse, we have similar philosophies
on how to solve
the problem.  It's probably worth some effort to figure out
the "right"
general solution.