Here's a Xen boot config generator for /etc/grub.d so you don't have to
manually create a 40-xen each time.

-Bruce

===cut===
#!/bin/bash -e
#===============================================================================
#
#          FILE:  09_xen
#
#         USAGE:  update-grub ... with this in /etc/grub.d
#
#   DESCRIPTION: Generate grub2 boot stanza for Xen systems
#                               Xen boot entries are automatically added to
grub.cfg
#                               The 09-... name prefix puts the Xen boot
entries before
#                               the linux kernel entries
#
#       OPTIONS:  ---
#  REQUIREMENTS:  --- grub2, Xen hypervisor
#          BUGS:  --- probably
#         NOTES:  --- Copied from 10_linux with a few hacks to make ir work
for Xen.
#                                       Incorporated suggestions to only do
this for valid dom0 kernels
#        AUTHOR:  Bruce Edge (BRE), <email address hidden>
#       COMPANY:  LSI
#       VERSION:  1.0
#       CREATED:  05/19/2010 02:32:34 PM PDT
#      REVISION:  ---
#===============================================================================

prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
. ${libdir}/grub/update-grub_lib

if [ "x${GRUB_DISTRIBUTOR}" = "x" ] ; then
  OS=GNU/Linux
else
  OS="${GRUB_DISTRIBUTOR}"
fi

# Source grub defaults
. /etc/default/grub

# loop-AES arranges things so that /dev/loop/X can be our root device, but
# the initrds that Linux uses don't like that.
case ${GRUB_DEVICE} in
  /dev/loop/*|/dev/loop[0-9])
    GRUB_DEVICE=`losetup ${GRUB_DEVICE} | sed -e
"s/^[^(]*(\([^)]\+\)).*/\1/"`
  ;;
esac

if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" =
"xtrue" ] \
    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" ; then
  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
else
  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi

test_gt ()
{
  local a=`echo $1 | sed -e
"s,.*/vmlinu[zx]-,,g;s/[._-]\(pre\|rc\|test\|git\|old\)/~\1/g"`
  local b=`echo $2 | sed -e
"s,.*/vmlinu[zx]-,,g;s/[._-]\(pre\|rc\|test\|git\|old\)/~\1/g"`
  if [ "x$b" = "x" ] ; then
    return 0
  fi
  dpkg --compare-versions "$a" gt "$b"
  return $?
}

find_latest ()
{
  local a=""
  for i in $@ ; do
    if test_gt "$i" "$a" ; then
      a="$i"
    fi
  done
  echo "$a"
}

list=`for i in /boot/vmlinu[xz]-* /vmlinu[xz]-* ; do
        if grub_file_is_not_garbage "$i" && grep -q 'DOM0=y'
${i/vmlinu[xz]/config} ; then echo -n "$i " ; fi
      done`

grep -q GRUB_CMDLINE_XEN_DEFAULT /etc/default/grub || list=""


while [ "x$list" != "x" ] ; do
  linux=`find_latest $list`
  echo "Found linux image: $linux" >&2
  basename=`basename $linux`
  dirname=`dirname $linux`
  rel_dirname=`make_system_path_relative_to_its_root $dirname`
  version=`echo $basename | sed -e "s,^[^0-9]*-,,g"`
  alt_version=`echo $version | sed -e "s,\.old$,,g"`
  linux_root_device_thisversion="${LINUX_ROOT_DEVICE}"

  initrd=
  for i in "initrd.img-${version}" "initrd-${version}.img" \
           "initrd.img-${alt_version}" "initrd-${alt_version}.img"; do
    if test -e "${dirname}/${i}" ; then
      initrd="$i"
      break
    fi
  done
  if test -n "${initrd}" ; then
    echo "Found initrd image: ${dirname}/${initrd}" >&2
  else
    # "UUID=" magic is parsed by initrds.  Since there's no initrd, it can't
work here.
    linux_root_device_thisversion=${GRUB_DEVICE}
  fi

  cat << EOF
  insmod lvm
  set root=(system-dom0_0)
menuentry "Xen ${OS}, linux ${version}" {
        multiboot /boot/xen.gz dummy=dummy $GRUB_CMDLINE_XEN_DEFAULT
        module ${rel_dirname}/${basename}
root=${linux_root_device_thisversion} $GRUB_CMDLINE_LINUX_DEFAULT
EOF
  if test -n "${initrd}" ; then
    cat << EOF
        module ${rel_dirname}/${initrd} ${rel_dirname}/${initrd}
EOF
  fi
  cat << EOF
}
EOF

  list=`echo $list | tr ' ' '\n' | grep -vx $linux | tr '\n' ' '`
done
===cut===