/mnt/gentoo/etc/grub.d/30_os-prober

cat /mnt/gentoo/etc/grub.d/30_os-prober
#! /bin/sh
set -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/>.

prefix=/usr
exec_prefix=${prefix}
libdir=/lib64

. ${libdir}/grub/grub-mkconfig_lib

if [ "x${GRUB_DISABLE_OS_PROBER}" = "xtrue" ]; then
  exit 0
fi

if [ -z "`which os-prober 2> /dev/null`" -o -z "`which linux-boot-prober 2> /dev/null`" ] ; then
  # missing os-prober and/or linux-boot-prober
  exit 0
fi

OSPROBED="`os-prober | tr ' ' '^' | paste -s -d ' '`"
if [ -z "${OSPROBED}" ] ; then
  # empty os-prober output, nothing doing
  exit 0
fi

osx_entry() {
        cat << EOF
menuentry "${LONGNAME} (${2}-bit) (on ${DEVICE})" --class osx --class darwin --class os {
EOF
        save_default_entry | sed -e "s/^/\t/"
        prepare_grub_to_access_device ${DEVICE} | sed -e "s/^/\t/"
        cat << EOF
        load_video
        set do_resume=0
        if [ /var/vm/sleepimage -nt10 / ]; then
           if xnu_resume /var/vm/sleepimage; then
             set do_resume=1
           fi
        fi
        if [ \$do_resume = 0 ]; then
           xnu_uuid ${OSXUUID} uuid
           if [ -f /Extra/DSDT.aml ]; then
              acpi -e /Extra/DSDT.aml
           fi
           $1 /mach_kernel boot-uuid=\${uuid} rd=*uuid
           if [ /System/Library/Extensions.mkext -nt /System/Library/Extensions ]; then
              xnu_mkext /System/Library/Extensions.mkext
           else
              xnu_kextdir /System/Library/Extensions
           fi
           if [ -f /Extra/Extensions.mkext ]; then
              xnu_mkext /Extra/Extensions.mkext
           fi
           if [ -d /Extra/Extensions ]; then
              xnu_kextdir /Extra/Extensions
           fi
           if [ -f /Extra/devprop.bin ]; then
              xnu_devprop_load /Extra/devprop.bin
           fi
           if [ -f /Extra/splash.jpg ]; then
              insmod jpeg
              xnu_splash /Extra/splash.jpg
           fi
           if [ -f /Extra/splash.png ]; then
              insmod png
              xnu_splash /Extra/splash.png
           fi
           if [ -f /Extra/splash.tga ]; then
              insmod tga
              xnu_splash /Extra/splash.tga
           fi
        fi
}
EOF
}

for OS in ${OSPROBED} ; do
  DEVICE="`echo ${OS} | cut -d ':' -f 1`"
  LONGNAME="`echo ${OS} | cut -d ':' -f 2 | tr '^' ' '`"
  LABEL="`echo ${OS} | cut -d ':' -f 3 | tr '^' ' '`"
  BOOT="`echo ${OS} | cut -d ':' -f 4`"

  if [ -z "${LONGNAME}" ] ; then
    LONGNAME="${LABEL}"
  fi

  echo "Found ${LONGNAME} on ${DEVICE}" >&2

  case ${BOOT} in
    chain)

      cat << EOF
menuentry "${LONGNAME} (on ${DEVICE})" --class windows --class os {
EOF
      save_default_entry | sed -e "s/^/\t/"
      prepare_grub_to_access_device ${DEVICE} | sed -e "s/^/\t/"

      case ${LONGNAME} in
        Windows\ Vista*|Windows\ 7*|Windows\ Server\ 2008*)
        ;;
        *)
          cat << EOF
        drivemap -s (hd0) \${root}
EOF
        ;;
      esac

      cat <<EOF
        chainloader +1
}
EOF
    ;;
    linux)
      LINUXPROBED="`linux-boot-prober ${DEVICE} 2> /dev/null | tr ' ' '^' | paste -s -d ' '`"
      prepare_boot_cache=

      for LINUX in ${LINUXPROBED} ; do
        LROOT="`echo ${LINUX} | cut -d ':' -f 1`"
        LBOOT="`echo ${LINUX} | cut -d ':' -f 2`"
        LLABEL="`echo ${LINUX} | cut -d ':' -f 3 | tr '^' ' '`"
        LKERNEL="`echo ${LINUX} | cut -d ':' -f 4`"
        LINITRD="`echo ${LINUX} | cut -d ':' -f 5`"
        LPARAMS="`echo ${LINUX} | cut -d ':' -f 6- | tr '^' ' '`"

        if [ -z "${LLABEL}" ] ; then
          LLABEL="${LONGNAME}"
        fi

        if [ "${LROOT}" != "${LBOOT}" ]; then
          LKERNEL="${LKERNEL#/boot}"
          LINITRD="${LINITRD#/boot}"
        fi

        cat << EOF
menuentry "${LLABEL} (on ${DEVICE})" --class gnu-linux --class gnu --class os {
EOF
        save_default_entry | sed -e "s/^/\t/"
        if [ -z "${prepare_boot_cache}" ]; then
          prepare_boot_cache="$(prepare_grub_to_access_device ${LBOOT} | sed -e "s/^/\t/")"
        fi
        printf '%s\n' "${prepare_boot_cache}"
        cat <<  EOF
        linux ${LKERNEL} ${LPARAMS}
EOF
        if [ -n "${LINITRD}" ] ; then
          cat << EOF
        initrd ${LINITRD}
EOF
        fi
        cat << EOF
}
EOF
      done
    ;;
    macosx)
      OSXUUID="`${grub_probe} --target=fs_uuid --device ${DEVICE} 2> /dev/null`"
      osx_entry xnu_kernel 32
      osx_entry xnu_kernel64 64
    ;;
    hurd)
      cat << EOF
menuentry "${LONGNAME} (on ${DEVICE})" --class hurd --class gnu --class os {
EOF
      save_default_entry | sed -e "s/^/\t/"
      prepare_grub_to_access_device ${DEVICE} | sed -e "s/^/\t/"
      grub_device="`${grub_probe} --device ${DEVICE} --target=drive`"
      mach_device="`echo "${grub_device}" | sed -e 's/(\(hd.*\),msdos\(.*\))/\1s\2/'`"
      grub_fs="`${grub_probe} --device ${DEVICE} --target=fs`"
      case "${grub_fs}" in
        *fs)    hurd_fs="${grub_fs}" ;;
        *)      hurd_fs="${grub_fs}fs" ;;
      esac
      cat << EOF
        multiboot /boot/gnumach.gz root=device:${mach_device}
        module /hurd/${hurd_fs}.static ${hurd_fs} --readonly \\
                        --multiboot-command-line='\${kernel-command-line}' \\
                        --host-priv-port='\${host-port}' \\
                        --device-master-port='\${device-port}' \\
                        --exec-server-task='\${exec-task}' -T typed '\${root}' \\
                        '\$(task-create)' '\$(task-resume)'
        module /lib/ld.so.1 exec /hurd/exec '\$(exec-task=task-create)'
}
EOF
    ;;
    *)
      echo "  ${LONGNAME} is not yet supported by grub-mkconfig." >&2
    ;;
  esac
done