Re: A thread on grub-bug could need attention

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Daniel Kiper wrote:
> IIRC you see blank screen after installing some distros. Right?

It also does not work when booting the ISO images which shall install
the systems.
E.g. debian-9.3.0-amd64-netinst.iso :

  mount debian-9.3.0-amd64-netinst.iso /mnt/iso
  mount /mnt/iso/boot/grub/efi.img /mnt/fat

At the end of the binary /mnt/fat/efi/boot/bootx64.efi, "strings" sees:

  search --file --set=root /.disk/info
  set prefix=($root)/boot/grub
  source $prefix/x86_64-efi/grub.cfg
  (memdisk)/boot/grub

The search leads to the ISO 9660 filesystem.
/mnt/iso/boot/grub/x86_64-efi/grub.cfg has

  insmod part_acorn
  insmod part_amiga
  insmod part_apple
  insmod part_bsd
  insmod part_dfly
  insmod part_dvh
  insmod part_gpt
  insmod part_msdos
  insmod part_plan
  insmod part_sun
  insmod part_sunpc
  source /boot/grub/grub.cfg

/mnt/iso/boot/grub/grub.cfg has

  if loadfont $prefix/font.pf2 ; then
    set gfxmode=800x600
    insmod efi_gop
    insmod efi_uga
    insmod video_bochs
    insmod video_cirrus
    insmod gfxterm
    insmod png
    terminal_output gfxterm
  fi
  
  if background_image /isolinux/splash.png; then
    set color_normal=light-gray/black
    set color_highlight=white/black
  else
    set menu_color_normal=cyan/blue
    set menu_color_highlight=white/blue
  fi
  
  insmod play
  play 960 440 1 0 4 440 1
  set theme=/boot/grub/theme/1
  menuentry --hotkey=g 'Graphical install' {
      set background_color=black
      linux    /install.amd/vmlinuz vga=788 --- quiet 
      initrd   /install.amd/gtk/initrd.gz
  }
  menuentry --hotkey=i 'Install' {
      set background_color=black
      linux    /install.amd/vmlinuz vga=788 --- quiet 
      initrd   /install.amd/initrd.gz
  }
  submenu --hotkey=a 'Advanced options ...' {
      set menu_color_normal=cyan/blue
      set menu_color_highlight=white/blue
      set theme=/boot/grub/theme/1-1
      menuentry '... Graphical expert install' {
          set background_color=black
          linux    /install.amd/vmlinuz priority=low vga=788 --- 
          initrd   /install.amd/gtk/initrd.gz
      }
      menuentry '... Graphical rescue mode' {
          set background_color=black
          linux    /install.amd/vmlinuz vga=788 rescue/enable=true --- quiet  
          initrd   /install.amd/gtk/initrd.gz
      }
      menuentry '... Graphical automated install' {
          set background_color=black
          linux    /install.amd/vmlinuz auto=true priority=critical vga=788 --- quiet 
          initrd   /install.amd/gtk/initrd.gz
      }
      menuentry --hotkey=x '... Expert install' {
          set background_color=black
          linux    /install.amd/vmlinuz priority=low vga=788 --- 
          initrd   /install.amd/initrd.gz
      }
      menuentry --hotkey=r '... Rescue mode' {
          set background_color=black
          linux    /install.amd/vmlinuz vga=788 rescue/enable=true --- quiet 
          initrd   /install.amd/initrd.gz
      }
      menuentry --hotkey=a '... Automated install' {
          set background_color=black
          linux    /install.amd/vmlinuz auto=true priority=critical vga=788 --- quiet 
          initrd   /install.amd/initrd.gz
      }
      submenu --hotkey=s '... Speech-enabled advanced options ...' {
          set menu_color_normal=cyan/blue
          set menu_color_highlight=white/blue
          set theme=/boot/grub/theme/1-1-1
          menuentry --hotkey=x '... Expert speech install' {
              set background_color=black
              linux    /install.amd/vmlinuz priority=low vga=788 speakup.synth=soft --- 
              initrd   /install.amd/gtk/initrd.gz
          }
          menuentry --hotkey=r '... Rescue speech mode' {
              set background_color=black
              linux    /install.amd/vmlinuz vga=788 rescue/enable=true speakup.synth=soft --- quiet  
              initrd   /install.amd/gtk/initrd.gz
          }
          menuentry --hotkey=a '... Automated speech install' {
              set background_color=black
              linux    /install.amd/vmlinuz auto=true priority=critical vga=788 speakup.synth=soft --- quiet 
              initrd   /install.amd/gtk/initrd.gz
          }
      }
  }
  menuentry --hotkey=s 'Install with speech synthesis' {
      set background_color=black
      linux    /install.amd/vmlinuz vga=788 speakup.synth=soft --- quiet 
      initrd   /install.amd/gtk/initrd.gz
  }

--------------------------------------------------------------------

Well, my MBR versus GPT theory fades away by Daniel Kiper's above question.

The next step would have been to build a grub-mkrescue image with
a partition layout like Knoppix 8.1. You'd take script
  xorriso-1.4.8/frontend/grub-mkrescue-sed.sh
from a GNU xorriso source installation or from
  https://dev.lovelyhq.com/libburnia/libisoburn/raw/master/frontend/grub-mkrescue-sed.sh
and use it as "xorriso" for the grub-mkrescue run.

It re-arranges the options for the xorriso run to achieve other partition
layouts and/or positions of the EFI System Partition.
Default is mode "mbr_only", which puts the EFI partition image after
the ISO 9660 partition and marks both partitions by MBR rather than GPT.

Best with xorrisofs option "-partition_offset 16", which lets the ISO
partition start at byte 32768 with an own superblock and directory tree,
while the overall ISO filesystem starts at byte 0 and claims the whole
image size including the EFI partition as its filesystem size.

  grub-mkrescue -o output.iso minimal \
                --xorriso=...path.../grub-mkrescue-sed.sh \
                -partition_offset 16  

If xorriso-1.4.8 is installed, you should afterwards get told by

  xorriso -indev output.iso -report_system_area plain

something like:

  System area summary: MBR grub2-mbr cyl-align-off
  ISO image size/512 : 33864
  Partition offset   : 16
  MBR heads per cyl  : 64
  MBR secs per head  : 32
  MBR partition table:   N Status  Type        Start       Blocks
  MBR partition      :   1   0x80  0x00           64        28040
  MBR partition      :   2   0x00  0xef        28104         5760

after this harmless warning:

  libisofs: WARNING : Found hidden El-Torito image. Its size could not be figured out, so image modify or boot image patching may lead to bad results.

(I will have to improve the multi-session capabilities with boot images
 which are not reachable as files of the ISO 9660 filesystem.)


Have a nice day :)

Thomas