Hi, Summary:
There are two EFI System Partitions in mini.iso. The one for booting from USB stick or qemu -hdb is indeed empty. One could try whether it helps to copy the files from the FAT image /boot/grub/efi.img in the ISO to MBR partition 2: - Put mini.iso onto a USB stick /dev/sdb or other hard disk device dd if=mini.iso of=/dev/sdb - Mount the ISO image mount -o loop mini.iso /mnt/iso - Mount the FAT filesystem inside /mnt/iso/boot/grub/efi.img mount -o loop /mnt/iso/boot/grub/efi.img /mnt/fat_iso - Mount the FAT filesystem in MBR partition 2 of the USB stick mount /dev/sdb2 /mnt/fat - Copy from efi.img into partition 2 of the USB stick: cp -a /mnt/fat_iso/* /mnt/fat - Check for sucessful copy: find /mnt/fat should yield /mnt/fat /mnt/fat/efi /mnt/fat/efi/boot /mnt/fat/efi/boot/bootx64.efi - Unmount what you mounted: umount /mnt/fat_iso /mnt/fat /mnt/iso - Try whether the stick boots via EFI. --------------------------------------------------------------- Details: Cyril Brulebois wrote: > I don't know much about EFI Partition etc. therefore I'm not > sure how they're related to an ISO9660 image. :/ mini.iso and debian-7*-amd64-netinst.iso differ in this aspect. In Debian amd64 netinst, the EFI System Partition is a data file inside the ISO filesystem which contains a FAT filesystem image. In this FAT image there are the files which EFI will use for booting. Debian has GRUB2 boot loader equipment in there. The block address and size of the EFI partition is published by an entry in the El Torito boot catalog, by a partition table entry in the MBR, by a partition table entry in GPT, and by a (probably useless) entry in Apple Partition Map. Inspecting mini.iso http://ftp.fr.debian.org/debian/dists/testing/main/installer-amd64/20150107/images/netboot/mini.iso by xorriso-1.3.8 yields: Volume id : 'ISOIMAGE' El Torito catalog : 59 1 El Torito cat path : /boot.cat El Torito images : N Pltf B Emul Ld_seg Hdpt Ldsiz LBA El Torito boot img : 1 BIOS y none 0x0000 0x00 4 8959 El Torito boot img : 2 UEFI y none 0x0000 0x00 832 9205 El Torito img path : 1 /isolinux.bin El Torito img opts : 1 boot-info-table isohybrid-suitable El Torito img path : 2 /boot/grub/efi.img System area options: 0x00000302 System area summary: MBR isohybrid cyl-align-all ISO image size/512 : 44332 Partition offset : 0 MBR heads per cyl : 64 MBR secs per head : 32 MBR partition table: N Status Type Start Blocks MBR partition : 1 0x80 0x17 0 45056 MBR partition : 2 0x00 0x01 45056 12288 So we have no GPT and no (probably useless) APM here. There are two EFI partitions exposed. One is the data file /boot/grub/efi.img of the ISO filesystem pointed to by the El Torito boot catalog. The other is an appended blob, marked by MBR partition 2. (The partition type 0x01 is questionable.) One can extract them by: mount -o loop mini.iso /mnt/iso cp /mnt/iso/boot/grub/efi.img eltorito_efi.img dd if=mini.iso bs=512 skip=45056 count=12288 of=mbr_efi.img Both files differ heavily in size -r--r--r-- 1 thomas thomas 425984 2015-01-27 09:59 eltorito_efi.img -rw-r--r-- 1 thomas thomas 6291456 2015-01-27 10:00 mbr_efi.img Inspecting both: $ mount -o loop eltorito_efi.img /mnt/fat $ find /mnt/fat /mnt/fat /mnt/fat/efi /mnt/fat/efi/boot /mnt/fat/efi/boot/bootx64.efi $ umount /mnt/fat $ mount -o loop mbr_efi.img /mnt/fat $ find /mnt/fat /mnt/fat $ So the El Torito advertised partition contains files, whereas the MBR advertised partition has an empty filesystem. Probably mini.iso will boot via EFI from CD/DVD/BD resp. qemu -cdrom, but not from USB stick resp. qemu -hdb. The presence of an isohybrid MBR will allow booting via BIOS emulation. --------------------------------------------------------------- For comparison the boot anatomy of a amd64 netinst ISO: $ xorriso-1.3.8 -indev debian-7.7.0-amd64-netinst.iso \ -report_el_torito plain -report_system_area plain ... Volume id : 'Debian 7.7.0 amd64 1' El Torito catalog : 847 1 El Torito cat path : /isolinux/boot.cat El Torito images : N Pltf B Emul Ld_seg Hdpt Ldsiz LBA El Torito boot img : 1 BIOS y none 0x0000 0x00 4 848 El Torito boot img : 2 UEFI y none 0x0000 0x00 896 860 El Torito img path : 1 /isolinux/isolinux.bin El Torito img opts : 1 boot-info-table isohybrid-suitable El Torito img path : 2 /boot/grub/efi.img System area options: 0x00000102 System area summary: MBR isohybrid cyl-align-on GPT APM ISO image size/512 : 454656 Partition offset : 0 MBR heads per cyl : 64 MBR secs per head : 32 MBR partition table: N Status Type Start Blocks MBR partition : 1 0x80 0x00 0 454656 MBR partition : 2 0x00 0xef 3440 896 MBR partition path : 2 /boot/grub/efi.img GPT : N Info GPT disk GUID : a0093564c5a7464b90530645ae2a43b6 GPT entry array : 12 208 overlapping GPT lba range : 64 454602 454655 GPT partition name : 1 490053004f00480079006200720069006400 GPT partname local : 1 ISOHybrid GPT partition GUID : 1 a0093564c5a7464b90510645ae2a43b6 GPT type GUID : 1 a2a0d0ebe5b9334487c068b6b72699c7 GPT partition flags: 1 0x1000000000000001 GPT start and size : 1 0 454600 GPT partition name : 2 490053004f004800790062007200690064003100 GPT partname local : 2 ISOHybrid1 GPT partition GUID : 2 a0093564c5a7464b90500645ae2a43b6 GPT type GUID : 2 a2a0d0ebe5b9334487c068b6b72699c7 GPT partition flags: 2 0x1000000000000001 GPT start and size : 2 3440 896 GPT partition path : 2 /boot/grub/efi.img APM : N Info APM block size : 2048 APM gap fillers : 0 APM partition name : 1 EFI APM partition type : 1 Apple_HFS APM start and size : 1 860 224 APM partition path : 1 /boot/grub/efi.img The file /boot/grub/efi.img contains similar stuff as the El Torito EFI partition of mini.iso : $ mount -o loop debian-7.7.0-amd64-netinst.iso /mnt/iso $ mount -o loop /mnt/iso/boot/grub/efi.img /mnt/fat $ find /mnt/fat /mnt/fat /mnt/fat/efi /mnt/fat/efi/boot /mnt/fat/efi/boot/bootx64.efi Note that all boot entrys for EFI point to the same file /boot/grub/efi.img inside the ISO filesystem. Partition editors hate this structure, though, because it represents overlapping (nested) partitions. An alternative is the product of GRUB2 script grub-mkrescue. Its partitions do not overlap (at the price that none of them represents a mountable ISO filesystem). Have a nice day :) Thomas -- To UNSUBSCRIBE, email to debian-cd-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: https://lists.debian.org/7332543323641545...@scdbackup.webframe.org