On s'intéresse ici au script /etc/grub.d/10_linux. Ce script génère les éléments du menu relatifs au système sur lequel on est.

1) NBLISTMAX:

Nombre de noyaux à afficher dans le menu.

2) PREFILTER et POSTFILTER:

Filtre sur le nom du noyau permettant de sélectionner les noyaux du système sur lequel on est, dans le cas ou la partition /boot est commune à plusieurs systèmes distincts.

Dans le cas de ubuntu Karmic, on a: PREFILTER="-2.6.31-" et POSTFILTER="-generic"

Nota: ces paramètres peuvent être mis à "" si /boot ne contient que les noyaux d'un unique système.

#! /bin/sh -e

# grub-mkconfig helper script.
# Copyright (C) 2006,2007,2008,2009  Free Software Foundation, Inc.
#
# GRUB 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 3 of the License, or
# (at your option) any later version.
#
# GRUB 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 GRUB.  If not, see <http://www.gnu.org/licenses/>.
#Modification-start
# Number of version to display - can be changed to desired value
NBLISTMAX=$((2))
# pre-filtering for kernel to use - can be changed to desired value
PREFILTER="-2.6.31-"
# post-filtering for kernel to use - can be changed to desired value
POSTFILTER="-generic"
# Intermediate variable - do not change
NBLIST=$((0))
#Modification-end


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



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

# 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/"`
    # We can't cope with devices loop-mounted from files here.
    case ${GRUB_DEVICE} in
      /dev/*) ;;
      *) exit 0 ;;
    esac
  ;;
esac

if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
    || [ "`grub-probe -t abstraction --device ${GRUB_DEVICE} | sed -e 's,.*\(lvm\).*,\1,'`" = "lvm"  ] ; then
  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
else
  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi

# add crashkernel option if we have the required tools
if [ -x "/usr/bin/makedumpfile" ] && [ -x "/sbin/kexec" ]; then
    GRUB_CMDLINE_EXTRA="$GRUB_CMDLINE_EXTRA crashkernel=384M-2G:64M,2G-:128M"
fi

linux_entry ()
{
  cat << EOF
menuentry "$1" {
        recordfail=1
        if [ -n \${have_grubenv} ]; then save_env recordfail; fi
EOF
  if [ "x$3" = "xquiet" ]; then
    cat << EOF
	set quiet=1
EOF
  fi
  save_default_entry | sed -e "s/^/\t/"
  prepare_grub_to_access_device ${GRUB_DEVICE_BOOT} | sed -e "s/^/\t/"
  cat << EOF
	linux	${rel_dirname}/${basename} root=${linux_root_device_thisversion} ro $2
EOF
  if test -n "${initrd}" ; then
    cat << EOF
	initrd	${rel_dirname}/${initrd}
EOF
  fi
  cat << EOF
}
EOF
}

list=`for i in /boot/vmlinu[xz]${PREFILTER}*${POSTFILTER} /vmlinu[xz]${PREFILTER}*${POSTFILTER} ; do
        if grub_file_is_not_garbage "$i" ; then echo -n "$i " ; fi
      done`

while [ "x$list" != "x" ] ; do
#LL-start
  NBLIST=$((NBLIST+1))
#  echo "NBLIST = $NBLIST" >&2
  linux=`version_find_latest $list`
  if [ "$NBLIST" -le "$NBLISTMAX" ] ; then
    echo "Found linux image: $linux" >&2
#LL-end
    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-${version}" "initrd.img-${alt_version}" \
	   "initrd-${alt_version}.img" "initrd-${alt_version}"; 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

    linux_entry "${OS}, Linux ${version}" \
      "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_EXTRA} ${GRUB_CMDLINE_LINUX_DEFAULT}" \
        quiet
    if [ "x${GRUB_DISABLE_LINUX_RECOVERY}" != "xtrue" ]; then
      linux_entry "${OS}, Linux ${version} (recovery mode)" \
	"single ${GRUB_CMDLINE_LINUX}"
    fi
#LL-start
  fi
#LL-end
  list=`echo $list | tr ' ' '\n' | grep -vx $linux | tr '\n' ' '`
#  echo "liste: $list" >&2

done