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I am building a custom iso using xorriso in mkisofs mode. The build seems correct, inspecting the iso afterwards shows 2 boot images (1 BIOS, 2 UEFI), yet booting to the ISO from qemu using the OVMF firmware fails to find any bootable media.

If I try the exact same boot in qemu but using a clean downloaded ubuntu 16.04 server iso, it boots without a problem.

If I use BIOS (not UEFI), both boot just fine.

xorriso command:

xorriso -as mkisofs \
   -l -J -R -V version \
   -no-emul-boot -boot-load-size 4 -boot-info-table \
   -b boot/isolinux/isolinux.bin -c boot/isolinux/boot.cat \
   -isohybrid-mbr isohhdpfx.bin \
   -eltorito-alt-boot -e EFI/BOOT/BOOTX64.EFI -no-emul-boot \
   -isohybrid-gpt-basdat \
   -o testos.iso ./cddir/

The details of examining the 2 iso (ubuntu and my custom built one) with xorriso -report_el_torito plain and cmd are in the following gist https://gist.github.com/deitch/e069268f92402d6a2b1c7e060ddba622

  • The program mkisofs does not have an option called -e. If you like to create a EFI boot, you would need to use -eltorito-platform EFI. .... Just in case you believe that xorriso implents the mkisofs behavior. There are more deviations, like the built in -findand UDF support in mkisofs that is missing from xorrise. – schily Jul 9 '18 at 11:54
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Thank you for flying xorriso.

The problem is in the image file which you let xorriso mark as EFI System Partition. It is supposed to be a FAT filesystem image which contains a binary file named /EFI/BOOT/BOOTX64.EFI (or .../BOOTIA32.EFI for 32 bit x86) plus possibly other files. Mount the file /boot/grub/efi.img from the Ubuntu ISO for learning about its content.

The FAT filesystems used by Ubuntu and others are probably produced by GRUB2 program grub-mkimage. ISOLINUX/SYSLINUX EFI software cannot be used because it bails out when seeing a CD-ROM device.

A quite convenient way to get a bootable ISO is program grub-mkrescue. If GRUB2 is configured for BIOS and EFI (e.g. by installing binary packages grub-pc, grub-efi-amd64, and grub-efi-ia32) then grub-mkrescue will produce an ISO which boots on BIOS and EFI of 32 bit and 64 bit x86 machines: El Torito boot images for BIOS and EFI, EFI image having BOOTX64.EFI and BOOTIA32.EFI, MBR for BIOS from hard disk, GPT for EFI from hard disk.

  • And I knew it! I knew it had to be not the EFI file, but the EFI file bound up in a single file vfat img... and completely forgot. Thank you, @ThomasSchmit! – deitch May 18 '16 at 8:11
  • And another problem; kernel options not being passed. They really did make this whole thing too hard! See unix.stackexchange.com/questions/283994/… – deitch May 18 '16 at 17:29
  • @GAD3R thanks for the updates. grub-mkrescue isn't relevant here, since I am working on a custom install iso. – deitch May 18 '16 at 17:30
  • FWIW, the kernel options was a grub2 bug. – deitch Jun 3 '16 at 9:02
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A very easy way to do it is this:

Append efi.img (from ubuntu ISO at boot/grub/efi.img) to your ISO and it will boot in every system.

cat efi.img >> youriso.iso

After that your ISO will work both as cdrom and as USB pendrive. :D

  • Seriously? It cannot be that simple. Why would I need to use xorriso with the complex options? – deitch Nov 30 '16 at 8:57
  • did you try it?! – Zibri Dec 27 '16 at 11:58
  • I didn't have the chance, but I will. It still boggles my mind that it can be that simple. – deitch Dec 31 '16 at 16:54
  • So is the simple method working ? – Overmind Feb 1 '17 at 12:22
  • Didn't work here. – Dominic Hayes Jul 12 '18 at 13:14

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