Make GRUB2 to add your Linux From Scratch to the boot-menu. !! READ THE COMMENTS !!

grubcfg-23_lfs.sh

#!/bin/sh
set -e

# Copyright (C) 2013  Ralf Stemmer (ralf.stemmer@gmx.net)                #
#                                                                        #
# 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 3 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, see <http://www.gnu.org/licenses/>.  #

# INSTALL:
##  cp -v ./grubcfg-23_lfs.sh /etc/grub.d/23_lfs
##  chmod +x /etc/grub.d/23_lfs
##  chmod -x /etc/grub.d/30_os-prober # optional

# how shall I call this OS
OSNAME="Linux From Scratch"

# give some parameters to the kernel
KERNELPARAMETERS="root=/dev/sda3"

# configure GRUB. This will be executed by grub before the kernel gets started
GRUBSETTINGS="load_video
set gfxpayload=keep
insmod part_msdos
insmod ext2
set root='hd0,msdos1'"

# where can I find the boot-partition?
# if it's a directory, the script looks for the kernel inside this directory.
# if it's a device, the script assumes this is the boot-partition and mounts it to PATH_TMPMP
# (you can use redundant paths)
PATH_BOOT=('/mnt/lfs/boot' '/dev/sda1')
#PATH_BOOT=('./fakeboot') # I used this to test the script :)
PATH_TMPMP='/mnt/tmp-42231337' # temporary mountpoint (will be removed after usage)


# Some helper-functions for logging
function print_headline
{
  echo -e "\n\e[1;36m$1\e[0m" >> /root/23_lfs.log
}
function print_step
{
 echo -e "\e[1;36m - \e[1;34m$1\e[0m" >> /root/23_lfs.log
}
function print_substep
{
 echo -e "  \e[0;36m · \e[0;36m$1\e[0m" >> /root/23_lfs.log
}


# look for the kernels we want top access with GRUB

print_headline "Preparing for $OSNAME-Boot-Entries"

for x in ${PATH_BOOT[@]} ; do
  print_step "Checking $x"
  DO_UNMOUNT="false" # true: $x was mounted temporarily, so unmount it
  DO_BREAK="false"   # true: Everything found, no further searching necessary

  # STEP 1: Prepare the directory (mount it if necessary)
  if [ -b $x ] ; then
    # $x is a device, lets see if it is mounted
    SEARCHPATH=$(mount | grep $x | cut -d ' ' -f 3)

    # $x seems not to be mounted, so let's mount it
    if [ ! -d "$SEARCHPATH" ] ; then
      print_substep "Mounting $x temporarily"
      SEARCHPATH=$PATH_TMPMP
      mkdir $SEARCHPATH
      mount $x $SEARCHPATH
      DO_UNMOUNT="true"
    else
      print_substep "$x is mounted to $SEARCHPATH"
    fi
  elif [ -d $x ] ; then
    # $x is a valid path, use it for searching
    print_substep "$x is a valid path"
    SEARCHPATH=$x
  else
    print_substep "$x is not a valid path"
    print_substep "\e[0;33m$x will be skipped"
    continue
  fi


  # STEP 2: Find all relevant files
  # So, now we have to find the files grub needs to boot
  #   vmlinuz*
  # !! NO INITRAMFS SUPPORTED, you may add this by your own if you need it
  #    You can handle them similar to vmlinuz*
  print_substep "Looking for relevant files …"
  if [ ! -d $SEARCHPATH ] ; then
    print_substep "\e[1;31mInvalid search-path ($SEARCHPATH) - Execution canceled"
    exit 1
  fi
  VMLINUZ=$(find $SEARCHPATH -maxdepth 1 -type f -iname "vmlinuz*" -exec basename {} \; | sort -r)

  # so, if we found the files, the loop can be left
  if [ "$VMLINUZ" ] ; then
    print_substep "\e[0;32mKernels found"
    DO_BREAK="true"
  fi


  # STEP 3: cleaning up
  if [ $DO_UNMOUNT == "true" ] ; then
    print_substep "Unmounting $x"
    umount $x
    rmdir $SEARCHPATH
  fi
  if [ $DO_BREAK == "true" ] ; then
    break
  fi
done


# just to be sure that everything is as expected during the next steps
if [ -z "$VMLINUZ" ] ; then
  print_headline "\e[1;31mNo relevant files found, execution canceled!"
  exit 1
fi

# put the list of files into an array
VMLINUZ_ARRAY=(${VMLINUZ// / })


# STEP 4: Create primary menu entry
VMLINUZ_ENTRY=${VMLINUZ_ARRAY[0]} # kernel for this entry
print_step "Create primary entry for $OSNAME with $VMLINUZ_ENTRY"

KERNEL_VERSION=${VMLINUZ_ENTRY#*-}
ENTRYNAME="$OSNAME (Linux $KERNEL_VERSION)"
# GRUBSETTINGS

cat << EOF
menuentry '$ENTRYNAME' --class gnu-linux --class gnu --class os {
        $GRUBSETTINGS
        echo 'Linux $KERNEL_VERSION wird geladen …'
        linux /$VMLINUZ_ENTRY $KERNELPARAMETERS
}
EOF


# STEP 5: Create sub-menu with older kernels
print_step "Create sub-menu for $OSNAME"

ENTRYNAME="Erweiterte Optionen für $OSNAME"

# start of submenu
cat << EOF
submenu '$ENTRYNAME' $menuentry_id_option {
EOF

# remove the latest version, this one was already handled
unset VMLINUZ_ARRAY[0]
# an entry for each kernel-version
for VMLINUZ_ENTRY in ${VMLINUZ_ARRAY[@]}
do
  KERNEL_VERSION=${VMLINUZ_ENTRY#*-}
  ENTRYNAME="$OSNAME (Linux $KERNEL_VERSION)"
  print_substep "Create entry for $OSNAME with $VMLINUZ_ENTRY"
  cat << EOF
  menuentry '$ENTRYNAME' --class gnu-linux --class gnu --class os {
          $GRUBSETTINGS
          echo 'Linux $KERNEL_VERSION wird geladen …'
          linux /$VMLINUZ_ENTRY $KERNELPARAMETERS
  }
EOF

done

# end of submenu
cat << EOF
}
EOF

exit 0