On Wed, 2019-02-13 at 20:57 +0100, Matthijs Kooijman wrote: > Package: live-build > Version: 1:20180925 > Severity: wishlist > > Hi folks, > > currently, live-build seems to only support EFI systems using the > grub-efi bootloader, but not for netboot or hdd images (effectively > only > for iso images, I believe). > > Syslinux also has an EFI version, that can be installed through > the syslinux-efi package. It would be useful for live-build to > support > this. I need this for a client, so I'm planning to implement support > in > the coming weeks. This report serves to track progress and discuss > the implementation. > > I've done some experiments by adding syslinux-efi to an existing > image > manually (not with a full live-build image, but with my own hdd image > that at least uses live-build for building the image, so should be > representative in this area). This shows that adding syslinux-efi is > fairly easy. The existing FAT partition can function as an ESP (EFI > System Partition) as it is now. > > Installing the bootloader is a matter of dumping some files in the > EFI/BOOT directory. This lets the bootloader be detected as a > fallback > bootloader, which is AFAIU intended for removable media. Syslinux > needs > some additional files (ldlinux, additional modules, configuration) > which > can live in that same directory. > > Both 32-bit and 64-bit EFI can be supported at the same time, by > installing both versions of syslinux-efi (named bootx64.efi and > bootia32.efi respectively). One caveat is that syslinux needs > different > .c32 modules for both architectures (though they are both named .c32 > and > are explicitly referenced in the config file). This means either > duplicating the bootloader configuration file for 32 and 64 bit > (which > hinders modifications to the config), or putting the modules in > subdirectories and using the PATH config directive to point to either > directive before including the common configuration. I have not tried > this latter approach but it is described here (though currently > syslinux.org seems to be unavailable, I tried the Google cache): > > https://www.syslinux.org/archives/2014-August/022545.html > > (subject: syslinux efi configuration file name proposal) > > I've also tried to let the syslinux-efi config file include the > normal > syslinux configuration file (or at least the bulk that is in > live.cfg), > which seems to work just fine. > > Since config sharing is easy and syslinux-efi is a matter of adding > some > files to the existing image, it would make sense to add syslinux-efi > by > default on normal syslinux hdd images (perhaps adding a new option to > disable this?). This also seems to hold for ISO9660 images, where > it seems isohybrid can include a small FAT filesystem with the > bootloader files. This might need some additional work to generate > the > filesystem image and/or pass options when generating the iso. See: > > https://www.syslinux.org/wiki/index.php?title=Isohybrid#UEFI > > > Using syslinux-efi exclusively (e.g. passing it to --bootloader and > not > installing normal syslinux) might also be an extra option. However, > I'm > not much interested in this case, so I will likely not implement it > (I'll try not to make it too hard to add it later). > > > In terms of code, this is probably best implemented in the existing > binary_syslinux script. The bulk of what needs to happen is > essentially > copying bootloader files from config/bootloaders into binary, taking > care to resolve symlinks. I'm planning to put the code that does that > into a shell function, so it can be called at the current place and > then > a second time for syslinux-efi later. > > I think it would be good to copy files *from* > config/bootloaders/syslinux-efi-addon or something similar, to leave > config/bootloaders/syslinux-efi available for an EFI-only image. > These > two directories would be identical in terms of syslinux binary files, > but the configurations would differ (the addon would include the > normal > boot/syslinux/syslinux.cfg, while the standalone version would > contain > the complete config). > > I haven't really looked at the iso version yet (which is also not my > primary interest, but I think it would be good to handle as well). > > Happy to hear any thoughts :-) > > Gr. > > Matthijs Hi, At a quick glance it all sounds good to me, although I can't say I have a lot of experience with syslinux. For feature parity, I'd encourage to look into supporting Secure Boot like the grub-efi implementation does, since we are preparing to ship that in Debian 10. It's not much extra work on top of adding the rest anyway. -- Kind regards, Luca Boccassi
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