Quoting http://www.syslinux.org/wiki/index.php/Isohybrid#UEFI: "The additional isohybrid feature for UEFI adds a partition to the MBR partition table pointing to the same file in the ISO 9660 filesystem as does the El Torito catalog entry for EFI." According to this (and can be see using fdisk) it's being created a partition-inside-partition just by setting its start and end sectors, so this could be done to be equal to the initial MBR partition generated by IsoHybrid, so there would not be duplicated files (kernel, initram and syslinus.cfg). Is that possible, currently or with some patches on isohybrid command? In what situations it would not work (iso9660 can be seen as a read-only FAT filesystem)? Also, could it be used directly the same MBR entry just by setting the partition entry flags or with some other minor tune-ups? -- "Si quieres viajar alrededor del mundo y ser invitado a hablar en un monton de sitios diferentes, simplemente escribe un sistema operativo Unix." ? Linus Tordvals, creador del sistema operativo Linux
> Quoting http://www.syslinux.org/wiki/index.php/Isohybrid#UEFI: > > "The additional isohybrid feature for UEFI adds a partition to the MBR > partition table pointing to the same file in the ISO 9660 filesystem > as does the El Torito catalog entry for EFI." > > According to this (and can be see using fdisk) it's being created a > partition-inside-partition just by setting its start and end sectors, > so this could be done to be equal to the initial MBR partition > generated by IsoHybrid, so there would not be duplicated files > (kernel, initram and syslinus.cfg). Is that possible, currently or > with some patches on isohybrid command? In what situations it would > not work (iso9660 can be seen as a read-only FAT filesystem)? Also, > could it be used directly the same MBR entry just by setting the > partition entry flags or with some other minor tune-ups? > > > > --I am replying to this email, but the content of your prior email might be relevant too. IMHO, the current content of the Isohybrid page in the Syslinux Wiki is not clear enough (in the past we have had here some discussion about the target audience of such page). The current generic information is rather focused on _potential_ capabilities of _isohybrid_ tools and some of their internal technical characteristics, and less focused on actual practical steps for ends users. The actual structure of the resulting partition table depends on the building tool in use. For example, there are several variants of the 'isohybrid' tool, and the 'xorriso' tool also provides isohybrid capabilities. Each tool might generate different partition tables for each isohybrid image (also depending on the options in use, of course). More importantly, part of the UEFI-related information in the aforementioned isohybrid wiki page also assumes a mix of preconditions, and some of them are not currently achievable by 'syslinux.efi'. Currently (as of v.6.03), 'syslinux.efi' does not support multiple volumes in the way that is currently described in the 'isohybrid' wiki page, so 'syslinux.efi' cannot simultaneously access both volumes, the ISO9660 volume and a FAT volume in an "efi.img". Additionally, currently 'syslinux.efi' has no support for ISO9660. So, even before evaluating whichever potential conflicts with specific hardware or with any variant of (U)EFI (e.g. EFI-based Macs) or with specific kernels, the fact is that 'syslinux.efi' could help you boot, for example, a USB flash drive formatted with FAT32, or a FAT EFI System Partition in your local disk drive, or network booting UEFI clients, but currently 'syslinux.efi' has no use for "efi.img" in a ISO9660 volume, and it cannot boot optical media in UEFI mode (with or without an "efi.img"). If you want to be able to boot a (FAT) storage media (such as a USB drive, among others) in UEFI mode, or network boot UEFI clients, then 'syslinux.efi' v.6.03 might be useful for you. The same ISO(hybrid) image could be used in systems with CSM mode in the same way as it is used in BIOS-based hardware (by means of ISOLINUX, for example). If you really need to boot optical media in UEFI mode, then you/we could wait some (long) time for potential developments in Syslinux, or you might want to consider other UEFI bootloaders, unfortunately. Regards, Ady.> _______________________________________________ > Syslinux mailing list > Submissions to Syslinux at zytor.com > Unsubscribe or set options at: > http://www.zytor.com/mailman/listinfo/syslinux
Hi, piranna wrote:> > Quoting http://www.syslinux.org/wiki/index.php/Isohybrid#UEFI: > > "The additional isohybrid feature for UEFI adds a partition to the MBR > > partition table pointing to the same file in the ISO 9660 filesystem > > as does the El Torito catalog entry for EFI."Ady wrote:> IMHO, the current content of the Isohybrid page in the Syslinux Wiki is > not clear enough [...] The current generic information is > rather focused on _potential_ capabilities of _isohybrid_ tools and > some of their internal technical characteristics, and less focused on > actual practical steps for ends users.Well, it is about really usable capabilities of isohybrid, which regrettably only work with EFI boot software from other bootloader projects. isohybrid can mark a FAT filesystem image with EFI boot software as EFI System Partition inside the ISO image. But SYSLINUX cannot provide a FAT image with EFI boot software that works with an ISO 9660 filesystem. All EFI isohybrid images known to me contain /efi/boot/bootx64.efi from GRUB Legacy or GRUB2. About fixing the wiki: Would it be appropriate to mention the words "GRUB legacy" and "GRUB2" in the SYSLINUX wiki ? Would it be desirable to explain how Fedora et.al. created their FAT boot images by help of old or new GRUB ? (If developers of EFI bootable ISOs are reading this, please give a short sketch of the procedure.) piranna wrote:> > (iso9660 can be seen as a read-only FAT filesystem)?The meta-data structures of ISO 9660 are different from FAT. Have a nice day :) Thomas
> I am replying to this email, but the content of your prior email might > be relevant too.Thank you :-)> IMHO, the current content of the Isohybrid page in the Syslinux Wiki is > not clear enough (in the past we have had here some discussion about > the target audience of such page). The current generic information is > rather focused on _potential_ capabilities of _isohybrid_ tools and > some of their internal technical characteristics, and less focused on > actual practical steps for ends users.I think the content although is not a step-by-step is good in general, but I need to expend several hours looking for internet to understand what the h*ll was the efiboot.img, what format it had and how to build it. Later I see it's explained there but not too clear since the text give the impression the file it's already there in the SysLinux files (similar to mbr.bin and others) and that it did a loopback from the EFI boot to the actual IsoLinux partition, not that it's an actual boot partition itself. This text definitely needs an update, because I was totally wrong here...> Currently (as of v.6.03), 'syslinux.efi' does not support multiple > volumes in the way that is currently described in the 'isohybrid' wiki > page, so 'syslinux.efi' cannot simultaneously access both volumes, the > ISO9660 volume and a FAT volume in an "efi.img". Additionally, > currently 'syslinux.efi' has no support for ISO9660. > > So, even before evaluating whichever potential conflicts with specific > hardware or with any variant of (U)EFI (e.g. EFI-based Macs) or with > specific kernels, the fact is that 'syslinux.efi' could help you boot, > for example, a USB flash drive formatted with FAT32, or a FAT EFI > System Partition in your local disk drive, or network booting UEFI > clients, but currently 'syslinux.efi' has no use for "efi.img" in a > ISO9660 volume, and it cannot boot optical media in UEFI mode (with or > without an "efi.img").Ok, since I'm mostly interested on using USB pendrives so we can consider that almost nobody will use a CD on an EFI-based computer (CDs are a good thing too, but who use them today? With BIOS-based computers support is just enough) and I'm writting the IsoHybrid image to an USB pendrive for my tests, crafting by hand (without the --uefi isohybrid argument) a volume (the ISO9660 one that later will be written to the USB, setting there the files from efiboot.img) marked with the esp flag and with the syslinux.efi file would work (so no need for efiboot.img), or does syslinux.efi needs support for ISO9660 first? As I said, syslinux.efi is reading the kernel.img and initrd.gz files from the efiboot.img image, but not booting them... :-/> If you want to be able to boot a (FAT) storage media (such as a USB > drive, among others) in UEFI mode, or network boot UEFI clients, then > 'syslinux.efi' v.6.03 might be useful for you. The same ISO(hybrid) > image could be used in systems with CSM mode in the same way as it is > used in BIOS-based hardware (by means of ISOLINUX, for example).Well, that's what tried first and didn't worked, on BIOS-based systems it boot but on my MacBook as Legacy OS didn't ("Operating System not found -- Insert disk and press any key"), that's why I started to experiment with EFI... :-/> If you really need to boot optical media in UEFI mode, then you/we > could wait some (long) time for potential developments in Syslinux, or > you might want to consider other UEFI bootloaders, unfortunately.Not at all. As I've said, booting from USB from an IsoHybrid-generated image on my MacBook is just enough, and in fact if I could do it in CSM mode I would remove EFI at all :-D -- "Si quieres viajar alrededor del mundo y ser invitado a hablar en un monton de sitios diferentes, simplemente escribe un sistema operativo Unix." ? Linus Tordvals, creador del sistema operativo Linux