Hi, Ady wrote:> * ISO images, > * burnt to _optical media_, > * and using then the resulting _optical media_ to boot in _UEFI mode_, > * in which the _main bootloader_ for such _optical media_ booting in > such _UEFI mode_ is part of The Syslinux Project.I would be willing to try such an ISO with qemu+OVMF. Regrettably my real test iron has no EFI firmware. Do you know the URL of a SYSLINUX EFI System Partition image that is known to boot from HD ? Or fool-proof instructions to build one ? I may have asked this already years ago. The long intervals between the discussions of this topic do not help me with keeping track. Whatever, now i have quite usable qemu-system-x86_64 and OVMF.fd of Debian 8. So i could pack a partition image into an ISO as EFI El Torito image and look whether it gives some signs of life as virtual CD-ROM.> At this point, some reader could interpret Peter's words as if this > situation could actually be successfully achieved.I explicitely asked him for clarification. Ping ?> I hope the current status would be improved in the (near) future.At least we need to put some tangible beef to the explanation of isohybrid.c option --uefi in the wiki. It would be helpful to get a hint from hpa, about what situation shall be described in the isohybrid wiki. Where any plans or decisions made when mjg implemented --uefi ? At that time it must have been obvious that Fedora Live CD would boot GRUB2 via EFI and not SYSLINUX. Have a nice day :) Thomas
On 04/02/16 04:18, Thomas Schmitt via Syslinux wrote:> > I may have asked this already years ago. The long intervals between > the discussions of this topic do not help me with keeping track. > Whatever, now i have quite usable qemu-system-x86_64 and OVMF.fd of > Debian 8. So i could pack a partition image into an ISO as EFI El Torito > image and look whether it gives some signs of life as virtual CD-ROM. > > >> At this point, some reader could interpret Peter's words as if this >> situation could actually be successfully achieved. > > I explicitely asked him for clarification. > > Ping ? > > >> I hope the current status would be improved in the (near) future. > > At least we need to put some tangible beef to the explanation of > isohybrid.c option --uefi in the wiki. > > It would be helpful to get a hint from hpa, about what situation shall > be described in the isohybrid wiki. > > Where any plans or decisions made when mjg implemented --uefi ? > At that time it must have been obvious that Fedora Live CD would boot > GRUB2 via EFI and not SYSLINUX. >I'm afraid I don't actually know a whole lot. At the time, I didn't have any system on which I could attempt to test this. I do now, but haven't had a chance to look at it. I'm not sure which is the intent of the El Torito spec and perhaps more importantly, what reality looks like, w.r.t. UEFI - whether it expects that the boot image is a partition or an EFI executable. In the latter case, syslinux.efi is probably 99% there. -hpa
Hi, hpa wrote:> I'm not sure which is the intent of the El Torito spec and perhaps more > importantly, what reality looks like, w.r.t. UEFI - whether it expects > that the boot image is a partition or an EFI executable.El Torito says nothing about EFI, but UEFI 2.4 describes an El Torito boot catalog entry with Platform Id 0xef (rather than 0 for x86 BIOS) as equivalent of a EFI System partition entry (MBR type 0xef or GPT with EFI Type GUID) if the device is an optical drive. (UEFI 2.4, 9.3.6.2 "CD-ROM Media Device Path") All known working boot images are FAT filesystem images with /EFI/BOOT/BOOT*.EFI files as first stage of the boot loader. The same boot image can be advertised as El Torito boot image (e.g. by ISO producer program), as MBR partition (e.g. by isohybrid --uefi or xorriso), or as GPT partitions (e.g. by grub-mkrescue + xorriso). This works with GRUB2, goofiboot, and Didier's all-in-one kernel as BOOT*.EFI file. The smallest EFI boot image known to me is in Debian amd64 netinst ISOs advertised by mjg's isohybrid --uefi layout: El Torito images : N Pltf B Emul Ld_seg Hdpt Ldsiz LBA El Torito boot img : 1 BIOS y none 0x0000 0x00 4 976 El Torito boot img : 2 UEFI y none 0x0000 0x00 832 996 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 ... MBR partition table: N Status Type Start Blocks MBR partition : 1 0x80 0x00 0 505856 MBR partition : 2 0x00 0xef 3984 832 MBR partition path : 2 /boot/grub/efi.img This boots with qemu-system-x86_64 via all four combinations of {BIOS, EFI} x {CD, HD} EFI (OVMF in my case) boots by this very sparse content of /boot/grub/efi.img : -rwxr-xr-x 1 root root 392192 Sep 6 2015 efi/boot/bootx64.efi -rwxr-xr-x 1 root root 1759 Apr 3 07:18 NvVars bootx64.efi has just enough of GRUB2 to read the configuration which is stored in /boot/grub of the ISO filesystem. One can spot at the end of the bootx64.efi file these GRUB2 configuration lines: search --file --set=root /.disk/info set prefix=($root)/boot/grub source $prefix/x86_64-efi/grub.cfg The meaning of "NvVars" is unclear to me. Program "file" says NvVars: Sendmail frozen configuration - version r But google relates the file name to OVMF. The failure symptom with SYSLINUX via EFI from CD-ROM is that it immediately reboots, probably after displaying a message about "Graphic" and a cursor underscore. (One needs a quick screen and fast eyes.) Have a nice day :) Thomas
> I'm not sure which is the intent of the El Torito spec and perhaps more > importantly, what reality looks like, w.r.t. UEFI - whether it expects > that the boot image is a partition or an EFI executable. >Neither. For booting optical media in UEFI mode (and, please let's leave comments about isohybrid out at this point) you need a partitionless (aka superfloppy) of less than 32MiB, with some additional alignment. I am purposely leaving out further / advanced possibilities. Let's not be picky. I would suggest solving the basic case first, and we can discuss further developments / options / alternatives later. Peter, see the attachment in: http://www.syslinux.org/archives/2015-October/024526.html for an example of what "should" eventually work in the future (when syslinux.efi gets the relevant capabilities). Regards, Ady.