ubuntu_linux /boot/grub/grub.conf解析

==========================================ubuntu  /boot/grub/grub.conf文件==========================================

#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
 set have_grubenv=true
 load_env
fi
if [ “${next_entry}” ] ; then
  set default=”${next_entry}”
  set next_entry=
  save_env next_entry
  set boot_once=true
else
  set default=”0″
fi

if [ x”${feature_menuentry_id}” = xy ]; then
 menuentry_id_option=”–id”
else
 menuentry_id_option=””
fi

export menuentry_id_option

if [ “${prev_saved_entry}” ]; then
 set saved_entry=”${prev_saved_entry}”
 save_env saved_entry
 set prev_saved_entry=
 save_env prev_saved_entry
 set boot_once=true
fi

function savedefault {
 if [ -z “${boot_once}” ]; then
   saved_entry=”${chosen}”
   save_env saved_entry
 fi
}
function recordfail {
 set recordfail=1
 if [ -n “${have_grubenv}” ]; then if [ -z “${boot_once}” ]; then save_env recordfail; fi; fi
}
function load_video {
 if [ x$feature_all_video_module = xy ]; then
   insmod all_video
 else
   insmod efi_gop
   insmod efi_uga
   insmod ieee1275_fb
   insmod vbe
   insmod vga
   insmod video_bochs
   insmod video_cirrus
 fi
}

if [ x$feature_default_font_path = xy ] ; then
  font=unicode
else
insmod part_msdos
insmod ext2
set root=’hd0,msdos1′
if [ x$feature_platform_search_hint = xy ]; then
 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
else
 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
fi
   font=”/usr/share/grub/unicode.pf2″
fi

if loadfont $font ; then
 set gfxmode=auto
 load_video
 insmod gfxterm
 set locale_dir=$prefix/locale
 set lang=en_US
 insmod gettext
fi
terminal_output gfxterm
if [ “${recordfail}” = 1 ] ; then
 set timeout=30
else
 if [ x$feature_timeout_style = xy ] ; then
   set timeout_style=hidden
   set timeout=0
 # Fallback hidden-timeout code in case the timeout_style feature is
 # unavailable.
 elif sleep –interruptible 0 ; then
   set timeout=0
 fi
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
### END /etc/grub.d/05_debian_theme ###

### BEGIN /etc/grub.d/10_linux ###
function gfxmode {
       set gfxpayload=”${1}”
       if [ “${1}” = “keep” ]; then
               set vt_handoff=vt.handoff=7
       else
               set vt_handoff=
       fi
}
if [ “${recordfail}” != 1 ]; then
 if [ -e ${prefix}/gfxblacklist.txt ]; then
   if hwmatch ${prefix}/gfxblacklist.txt 3; then
     if [ ${match} = 0 ]; then
       set linux_gfx_mode=keep
     else
       set linux_gfx_mode=text
     fi
   else
     set linux_gfx_mode=text
   fi
 else
   set linux_gfx_mode=keep
 fi
else
 set linux_gfx_mode=text
fi
export linux_gfx_mode
menuentry ‘Ubuntu’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-simple-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
       recordfail
       load_video
       gfxmode $linux_gfx_mode
       insmod gzio
       insmod part_msdos
       insmod ext2
       set root=’hd0,msdos1′
       if [ x$feature_platform_search_hint = xy ]; then
         search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
       else
         search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
       fi
       linux   /boot/vmlinuz-4.4.0-72-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
       initrd  /boot/initrd.img-4.4.0-72-generic
}
submenu ‘Advanced options for Ubuntu’ $menuentry_id_option ‘gnulinux-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
       menuentry ‘Ubuntu, with Linux 4.4.0-72-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-72-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-72-generic …’
               linux   /boot/vmlinuz-4.4.0-72-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-72-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-72-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-72-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-72-generic …’
               linux   /boot/vmlinuz-4.4.0-72-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-72-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-66-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-66-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-66-generic …’
               linux   /boot/vmlinuz-4.4.0-66-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-66-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-66-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-66-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-66-generic …’
               linux   /boot/vmlinuz-4.4.0-66-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-66-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-64-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-64-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-64-generic …’
               linux   /boot/vmlinuz-4.4.0-64-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-64-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-64-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-64-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-64-generic …’
               linux   /boot/vmlinuz-4.4.0-64-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-64-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-59-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-59-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-59-generic …’
               linux   /boot/vmlinuz-4.4.0-59-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-59-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-59-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-59-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-59-generic …’
               linux   /boot/vmlinuz-4.4.0-59-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-59-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-57-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-57-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-57-generic …’
               linux   /boot/vmlinuz-4.4.0-57-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-57-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-57-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-57-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-57-generic …’
               linux   /boot/vmlinuz-4.4.0-57-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-57-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-53-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-53-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-53-generic …’
               linux   /boot/vmlinuz-4.4.0-53-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-53-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-53-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-53-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-53-generic …’
               linux   /boot/vmlinuz-4.4.0-53-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-53-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-45-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-45-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-45-generic …’
               linux   /boot/vmlinuz-4.4.0-45-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-45-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-45-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-45-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-45-generic …’
               linux   /boot/vmlinuz-4.4.0-45-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-45-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-42-generic’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-42-generic-advanced-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               gfxmode $linux_gfx_mode
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-42-generic …’
               linux   /boot/vmlinuz-4.4.0-42-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US quiet
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-42-generic
       }
       menuentry ‘Ubuntu, with Linux 4.4.0-42-generic (recovery mode)’ –class ubuntu –class gnu-linux –class gnu –class os $menuentry_id_option ‘gnulinux-4.4.0-42-generic-recovery-87f8333a-b6dc-49f7-89f9-ef6a91eb756b’ {
               recordfail
               load_video
               insmod gzio
               insmod part_msdos
               insmod ext2
               set root=’hd0,msdos1′
               if [ x$feature_platform_search_hint = xy ]; then
                 search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               else
                 search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
               fi
               echo    ‘Loading Linux 4.4.0-42-generic …’
               linux   /boot/vmlinuz-4.4.0-42-generic root=UUID=87f8333a-b6dc-49f7-89f9-ef6a91eb756b ro recovery nomodeset find_preseed=/preseed.cfg auto noprompt priority=critical locale=en_US
               echo    ‘Loading initial ramdisk …’
               initrd  /boot/initrd.img-4.4.0-42-generic
       }
}

### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/20_linux_xen ###

### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry ‘Memory test (memtest86+)’ {
       insmod part_msdos
       insmod ext2
       set root=’hd0,msdos1′
       if [ x$feature_platform_search_hint = xy ]; then
         search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
       else
         search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
       fi
       knetbsd /boot/memtest86+.elf
}
menuentry ‘Memory test (memtest86+, serial console 115200)’ {
       insmod part_msdos
       insmod ext2
       set root=’hd0,msdos1′
       if [ x$feature_platform_search_hint = xy ]; then
         search –no-floppy –fs-uuid –set=root –hint-bios=hd0,msdos1 –hint-efi=hd0,msdos1 –hint-baremetal=ahci0,msdos1  87f8333a-b6dc-49f7-89f9-ef6a91eb756b
       else
         search –no-floppy –fs-uuid –set=root 87f8333a-b6dc-49f7-89f9-ef6a91eb756b
       fi
       linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###

### BEGIN /etc/grub.d/30_os-prober ###
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/30_uefi-firmware ###
### END /etc/grub.d/30_uefi-firmware ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the ‘exec tail’ line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f  ${config_directory}/custom.cfg ]; then
 source ${config_directory}/custom.cfg
elif [ -z “${config_directory}” -a -f  $prefix/custom.cfg ]; then
 source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###

============================================================================================

default=数字：默认启动的操作系统，数字0表示第一个标题，1表示第二个，以此类推；

timeout=数字：一般选项界面出现的时间，单位秒；

root（装置）：指定内核或操作系统所在的磁盘与分区，格式为（hdx，y），其中x表示第x个磁盘，y表示第y个分区，如root（hd0,1）；

initrd 文件：制定系统加载时所需要的内存磁盘以映像，同样的，文件所在的位置必须在root所定义的磁盘之下；

============================================================================================

run level

Linux的运行层级（run level）共7个，

0：关机；

1：单人模式；

2/3/4/5:因不同的发行商而异；Feroda:2–>缺少部分网络功能的文字界面模式，3–>完整功能的文字界面模式，4–>保留，可自定义；5–>完整功能的图形界面模式；

6：重新启动系统；

=====================================================================================================

过程解析

BIOS—》stage1—》stage1.5—》stage2—》vmlinuxz—》initrd—》读取/etc/event.d/rc-default—–未定义/etc/inittab>启动runlevel2——————|—-》启动画面

                                       ＧＲＵＢ                 内核                                          |_____定义/etc/inittab(默认)>根据/etc/inittab定义的runlevel进行启动—|

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

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