There is an easy way to check if -k can be used always: have a look at windows install CD/DVD. If it doesn't have partion table then we can drop it as well.
On Thu, 25 Apr 2019, 18:16 Thomas Schmitt, <scdbac...@gmx.net> wrote: > Hi, > > Daniel Kiper wrote: > > How do you create USB stick from ISO image? > > By plain copy to the base device, as usual for a grub-mkrescue ISO. > Like > > dd if=image of=usb_stick > > > > Have you tried latest Guix image? > > Florian builds Guix ISOs locally. So i assume that it was newest Guix. > Nevertheless, the problem is clearly not in Guix content but in the > Start LBA 0 of the partition table entry inside the EFI partition image. > > > > Numbers here and in another email suggest that this is a floppy image. > > And floppy images do not have MBR. They have something called boot > > sector which is a bit different thing. > > Yes. It already has been pointed out to me privately that it should > rather be called a "VBR". > But EFI specs talk of "MBR" in the System Partition. So i am in good > company. As mathematician i always agree to "If it walks like a duck ...". > > UEFI 2.4, 12.3.1 "System Partition" > > "A System Partition supports backward compatibility with legacy systems > by reserving the first block (sector) of the partition for compatibility > code. On legacy systems, the first block (sector) of a partition is > loaded into memory and execution is transferred to this code. > EFI firmware does not execute the code in the MBR. The EFI firmware > contains knowledge about the partition structure of various devices, > and can understand legacy MBR, GPT, and “El Torito.”" > > (The description of BIOS loading partition boot code is wrong. It is a > class of device MBRs which contain code to chainload partition boot code. > I guess, GRUB has such an MBR variant in its collection, too.) > > The last sentence might mean that EFI shall support extended MBR > partitions. > I doubt that it is an invitation to support a tree of partition tables with > arbitrary tree width. > I also doubt that the author had a mental relapse to the MBR of the device, > which is mentioned in the paragraph before the one above. > > "A System Partition is a partition in the conventional sense of a > partition on a legacy system. For a hard disk, a partition is a > contiguous grouping of sectors on the disk where the starting sector > and size are defined by the Master Boot Record (MBR), which resides > on LBA 0 (i.e., the first sector of the hard disk) (see Section 5.2), > or the GUID Partition Table (GPT), which resides on logical block 1 > (the second sector of the hard disk) (see Section 5.3.1). For a > diskette (floppy) drive, a partition is defined to be the entire media. > A System Partition can reside on any media that is supported by EFI > Boot Services." > > > > I have a feeling that simply Macs > > tested by you does not like floppy images. If you create regular HDD > > images then probably everything will work. > > It was grub-mkrescue which created that floppy image by mformat > and submits it to xorriso as EFI partition. > > My questions were whether the partition entry is necessary (Vladimir > expects that it is not), and whether an MBR signature and the other > fields in block 0 are needed, which mformat creates without option -k > (Vladimir's answer was less firm). > > I am now proposing to Guix to use my script-in-the middle > > > https://dev.lovelyhq.com/libburnia/libisoburn/raw/master/frontend/grub-mkrescue-sed.sh > > which is submitted to grub-mkrescue by option --xorriso=. > > Its main purpose is to achieve other partition layouts with mountable > ISO partition. Meanwhile it learned how to zeroize the partition table > in the EFI partition and, if desired additionally, to zeroize the MBR > signature of the partition. > > Be invited to try with a BIOS and EFI enabled GRUB configuration: > > wget > https://dev.lovelyhq.com/libburnia/libisoburn/raw/master/frontend/grub-mkrescue-sed.sh > chmod u+x grub-mkrescue-sed.sh > > export MKRESCUE_SED_MODE=mbr_hfs > export MKRESCUE_SED_IN_EFI_NO_PT=yes > > grub-mkrescue --xorriso=./grub-mkrescue-sed.sh \ > -iso_mbr_part_type 0x83 -partition_offset 16 \ > ...your usual options to grub-mkrescue... > > ( export MKRESCUE_SED_DEBUG=yes > would let the script print input xorriso arguments and the arguments > which it actually hands over to xorriso.) > > The result has this partition layout: > > $ /sbin/fdisk -l output.iso > ... > Disklabel type: dos > ... > Device Boot Start End Sectors Size Id Type > output.iso1 * 64 28695 28632 14M 83 Linux > output.iso2 28696 34455 5760 2.8M ef EFI (FAT-12/16/32) > > Advantages in my eyes are: > > - No GPT backup which will be misplaced on USB stick after dd. > (Linux and partition editors complain.) > > - Mountable ISO partition with non-zero partition start for pleasing > partition editors and being able to claim partition 2 as part of the > filesystem range of the base device ISO: > $ expr $(/sbin/isosize /dev/sdc) / 512 > 34456 > $ expr $(/sbin/isosize /dev/sdc1) / 512 > 28632 > This maintains the property of the original grub-mkrescue GPT layout, > that an ISO image on a USB stick or DVD+RW still can tell its original > size for checksumming. > > - It is supposed to boot on Florian's Macbook because of no partition table > in the EFI partition. (I'm not sure whether Florian aready tested it. > Our test results are from byte hacking experiments on a vanilla Guix > ISO.) > > > Have a nice day :) > > Thomas > > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > https://lists.gnu.org/mailman/listinfo/grub-devel >
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