Hi, i'm the developer of xorriso. Please CC me with replies just in case that i unsubscribe because of too much traffic. Further: Sorry for my reply-id pointing to the predecessor of the message which i quote. I found it at https://www.spinics.net/lists/fedora-devel/msg299915.html Chris Murphy wrote: > For what it's worth, the current xorriso command used [...] is > > xorrisofs -o /var/tmp/lmc-work-hrb6zq5j/images/boot.iso > -isohybrid-mbr /usr/share/syslinux/isohdpfx.bin > -b isolinux/isolinux.bin > -c isolinux/boot.cat > -boot-load-size 4 -boot-info-table -no-emul-boot > -eltorito-alt-boot > -e images/efiboot.img -no-emul-boot -isohybrid-gpt-basdat > -eltorito-alt-boot > -e images/macboot.img -no-emul-boot -isohybrid-gpt-hfsplus > -R -J -V Fedora-WS-Live-36-20220407-n-0 > -graft-points > [... various files and directories grafted in ...] > > There's a bit to unpack there... The lines, which will need changes for using GRUB, are at least: -isohybrid-mbr /usr/share/syslinux/isohdpfx.bin [...] -boot-load-size 4 -boot-info-table -no-emul-boot -b isolinux/isolinux.bin grub-mkrescue (on Debian) uses instead: --grub2-mbr /usr/lib/grub/i386-pc/boot_hybrid.img -b boot/grub/i386-pc/eltorito.img -no-emul-boot -boot-load-size 4 -boot-info-table --grub2-boot-info /usr/lib/grub/i386-pc/boot_hybrid.img is part of Debian's grub-pc-bin package. It gets built by upstream file grub-core/Makefile.core https://sources.debian.org/src/grub2/2.06-2/grub-core/Makefile.core.am/?hl=23370#L23370 /boot/grub/i386-pc/eltorito.img has to be inserted as data file into the emerging ISO 9660 filesystem. grub-mkrescue puts it into the file tree on hard disk which it then gives to xorrisofs as input file. It gets produced by GRUB from a file named "cdboot.img". In Debian it is part of package grub-pc-bin as /usr/lib/grub/i386-pc/cdboot.img It does not appear as if the read-in cdboot.img would get modified before it gets written back as "eltorito.img": https://sources.debian.org/src/grub2/2.06-2/util/mkimage.c/?hl=1271#L1266 Its production/copying gets ordered in: https://sources.debian.org/src/grub2/2.06-2/util/grub-mkrescue.c/?hl=598#L584 The emerging GRUB MBR is supposed to boot from USB sticks quite like the ISOLINUX MBR. Both hop with their execution onto the El Torito boot images for BIOS. grub-mkrescue uses no option -c, which does not matter for boot success. Fedora can well keep its -c isolinux/boot.cat The EFI-related options -isohybrid-gpt-basdat and -isohybrid-gpt-hfsplus will continue to work, if additionally option -part_like_isohybrid is given (once is enough). ------------------------------------------------------------------------ More unsolicited info: An opportunity to watch grub-mkrescue's xorriso options is given by the script frontend/grub-mkrescue-sed.sh from the source tarball of xorriso (which in Fedora is libisoburn-*.tar.gz): https://dev.lovelyhq.com/libburnia/libisoburn/raw/branch/master/frontend/grub-mkrescue-sed.sh I derived above BIOS proposal by mkdir minimal touch minimal/empty-file.txt export MKRESCUE_SED_DEBUG=yes grub-mkrescue -o output.iso minimal \ --xorriso=/...localpath.../frontend/grub-mkrescue-sed.sh If i install (on Debian) grub-common grub-pc-bin grub-efi-amd64-bin grub-efi-ia32-bin i get from grub-mkrescue an ISO with both, BIOS and EFI equipment. The original purpose of the script grub-mkrescue-sed.sh is to enable variations of the xorriso options to create different layouts of partition tables for the EFI stuff. See "Variation settings" in the script. The main drawback of grub-mkrescue's original partition layout is that there is no mountable partition for the ISO 9660 filesystem. For Fedora's ISOs it might be interesting to inspect the messages and the resulting ISO of export MKRESCUE_SED_MODE=mjg export MKRESCUE_SED_DEBUG=yes grub-mkrescue -o output.iso minimal \ --xorriso=/...localpath.../frontend/grub-mkrescue-sed.sh It produces a layout that is inspired by mjg59's from 2012, but avoids to have the EFI partition inside the ISO 9660 filesystem and its partition by appending the EFI partition. (The HFS+ filesystem for Macs gets produced by libisofs. It would be interesting to learn whether such Macs still exist and work with the grub-mkrescue ISO.) Discussions with other distro's ISO maintainers and their users yielded that some old BIOS machines demand an MBR partition with "boot/active" flag. Some new EFIs demand the presence of a GPT. So ye olde nested pseudo-GPT partition layout of Fedora (and also of Debian) still has its merits. Just the nesting is ugly, unneeded, and causes protests from partition editors. With original grub-mkrescue layout and its pure GPT, the remedy is to use xorrisofs option --mbr-force-bootable which makes the GPT a bit less pure by adding a little dummy MBR partition of type 0x00. Have a nice day :) Thomas _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
