Hi, this could be a bug in live-build.
It seems to use "xorriso -as mkisofs" option -isohybrid-mbr on systems which have no PC-BIOS firmware and thus get no ISOLINUX BIOS bot equipment in the ISO. Line 69 in https://sources.debian.org/src/live-build/1:20210122/scripts/build/binary_iso/ adds -isohybrid-mbr to the options without checking that LB_BOOTLOADER_BIOS is set to "syslinux". But only with this setting, the option -b isolinux/isolinux.bin is used, which is a precondition for using -isohybrid-mbr. (Option -partition_offset 16 would be ok without "syslinux".) ------------------------------------------------------------------------ Long story: I am the developer of libisofs. The error message is sparse, i have to confess. Code study shows three occasions where libisofs: MISHAP : Cannot patch isolinux boot image can be emitted without more explanation. 1: The size of the El Torito boot image file isolinux.bin is less than 64 bytes. So it cannot take a Boot Info Table. 2: There was no isolinux.bin submitted at all. (option -b in mkisofs emulation, or command -boot_image isolinux dir=/isolinux in native command mode.) 3: is like 2 in a different code path. I can provoke the sparse message by omitting -b and its subordinates: xorriso -as mkisofs -o /dev/null -isohybrid-mbr "$HOME"/x "$HOME"/xx with "$HOME"/x and "$HOME"/xx being some small dummy files: ... xorriso : NOTE : Copying to System Area: 36 bytes from file '[...]/x' libisofs: MISHAP : Cannot patch isolinux boot image xorriso : FAILURE : Failed to prepare session write run ... That would be occasion 3. Now why should there be no -b isolinux/isolinux.bin ? Do i get it right, that the xorriso run is started by https://sources.debian.org/src/live-build/1:20210122/scripts/build/binary_iso/ ? (Would it be possible to let the script report the actual xorriso arguments ?) My best guess is that variable LB_BOOTLOADER_BIOS is not set to "syslinux". It controls in line 110 ff. which BIOS boot equipment is to be submitted by option -b. The option -isohybrid-mbr is used if LB_IMAGE_TYPE is "iso-hybrid" (line 66 ff.). This seems wrong, because it is used even if no ISOLINUX is selected by LB_BOOTLOADER_BIOS. So if amd64 and i386 succeed, it is most probably the inappropriate option -isohybrid-mbr which spoils the runs for the others. Have a nice day :) Thomas