Thomas, Thank you for clarification on the layout, as it is in fact most helpful in understanding GPT cruft. As a Gentoo user, I can in fact boot system-rescue-cd and Knoppix as EFI USB. Sadly, this seems like one more nail in the coffin of reasons I need to upgrade my PC. I cannot reproduce the boot error on a dell system either.
Thank you for your support and time. On Sat, Sep 15, 2018 at 07:09:58PM +0200, Thomas Schmitt wrote: > Hi, > > John Roman wrote: > > As I understand, a Protective MBR may be located at LBA 0 > > In the case of the isohybrid partition layout of Matthew J. Garrett, > which is used by Debian for i386 and amd64, the MBR is not protective. > > A bit confusing can be the GPT partition table debris that follows the MBR. > It is supposed to be ignored by any entity which cares about GPT specs. > Matthew presented his layout at > http://mjg59.dreamwidth.org/11285.html > He talks of Fedora ISOs. Debian joined that layout, but without HFS+ > filesystem. > > > > is this what the live image does > > From the view of EFI and many partition editors, Debian's ISO MBR > effectively marks only one partition, the EFI partition, as entry number 2. > > Entry number 1 has type 0x00 to avoid rejection by EFI due to partition 2 > sitting inside partition 1. UEFI 2.4, 5.2.1 specifies: > "A Partition Record that contains an OSType value of zero or a SizeInLBA > value of zero may be ignored." > Partition 1 exists to mark the size of the ISO 9660 filesystem. It is not > supposed to matter during booting. (BIOS boots by the MBR x86 machine code.) > > > > my desktop (2012) does not seem to understand 0xEF...I wish I knew why. > > If you have access to a running Debian System, then you could build a > grub-mkrescue ISO, which will have a protective MBR and valid GPT. > If it boots to a GRUB prompt, then we know that your machine would work > with GPT. > > Try to create it with these commands ("minimal/file" is just to have a > directory and file, on which grub-mkrescue insists): > > sudo apt-get install grub-pc grub-efi-ia32-bin grub-efi-amd64-bin xorriso > mkdir minimal > echo hello >minimal/file > grub-mkrescue -o output.iso minimal > > Put output.iso onto an USB stick, as you did with the Debian ISO. > > ------- > > Another test proposal: > > Knoppix 8.1 ISOs have a different MBR based partition layout than Fedora, > Debian, et.al. If Knoppix 8.1 (or newer version) boots, then your > firmware probably hates that Debian partition 1 encloses partition 2, > despite its type 0x00. > (Knoppix 8.0 has a partition layout like Debian, but with appended > partition 3 of type 0x83. Knoppix 7 has no partition table at all.) > > > Have a nice day :) > > Thomas >
