Difference between revisions of "Talk:Unified Extensible Firmware Interface"

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(Remove UEFI boot support from optical media: re)
(Answered to nl6720)
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:To clarify, this was just a wild guess after reading [https://lists.gnu.org/archive/html/grub-devel/2019-06/msg00000.html]. I didn't meant to ask if "omitting the partition table in the ISO would disable EFI booting from optical media". The question was meant to be, can the affected Macs boot the ISO if it is built with {{ic|1=partition_table=off}} without further modifications? I.e. could the Archiso be ''fixed'' by using that option of xorriso? -- [[User:nl6720|nl6720]] ([[User talk:nl6720|talk]]) 06:43, 29 June 2019 (UTC)
 
:To clarify, this was just a wild guess after reading [https://lists.gnu.org/archive/html/grub-devel/2019-06/msg00000.html]. I didn't meant to ask if "omitting the partition table in the ISO would disable EFI booting from optical media". The question was meant to be, can the affected Macs boot the ISO if it is built with {{ic|1=partition_table=off}} without further modifications? I.e. could the Archiso be ''fixed'' by using that option of xorriso? -- [[User:nl6720|nl6720]] ([[User talk:nl6720|talk]]) 06:43, 29 June 2019 (UTC)
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::The answer is no. The xorriso command {{ic|1=-boot_image partition_table=off}} would only hamper booting from USB stick. Optical media are supposed to be inspected for an El Torito catalog, which should have an entry for "platform" EFI. I was involved in that discussion on grub-devel. The Mac problem there was that the EFI partition itself contained again a partition table. For some reason two old MacBooks took offense. But this surplus table is not present in Arch ISOs, because its EFI partition image is not made by program "mformat". (We found it in the Guix distro which uses program grub-mkrescue for creating its ISOs.) [[User:Scdbackup|Scdbackup]] ([[User talk:Scdbackup|talk]]) 07:07, 29 June 2019 (UTC)

Revision as of 07:07, 29 June 2019

bcdedit

I do not think that the command

# bcdedit /set {bootmgr} path \EFI\path\to\app.efi

"tell the Windows boot loader to run a different UEFI application" as mentioned in the wiki (in the "Windows changes boot order" section) I think it add an entry in the UEFI firmware. But that can be as well accomplished under Linux with efibootmgr command. If the UEFI is weird (by refusing to boot something other than Windows for example); I do not think it will be of any help. I am not a Windows specialist and so I do not take the responsibility to edit this section, but someone more knowledgeable than me should double check it.

—This unsigned comment is by Olive (talk) 13:00, 20 September 2016‎. Please sign your posts with ~~~~!

From my reading, it seems that this command should trick windows into running a different EFI application instead of its own boot manager (bootmgfw.efi). I don't have the means to test it right now, but given that there are plenty of other recommendations in the article, I don't think it hurts to keep this command around. We'll just have to wait until someone gives it a test. Silverhammermba (talk) 15:35, 20 September 2016 (UTC)
The `bcdedit` command causes Windows to chainload the named .efi loader, no new NVRAM entries are made. Head on a Stick (talk) 15:49, 23 March 2019 (UTC)

Remove UEFI boot support from optical media

The question was posed in an "Expansion" box, whether omitting the partition table in the ISO would disable EFI booting from optical media. It would not, because the UEFI specs say that optical media shall boot via El Torito, not via partition table. The partition table is used if the image is presented on hard-disk-like storage media. (In practice, several EFI implementations happily ignore this difference. But the Macs in question seem to respect it.) Scdbackup (talk) 06:34, 29 June 2019 (UTC)

To clarify, this was just a wild guess after reading [1]. I didn't meant to ask if "omitting the partition table in the ISO would disable EFI booting from optical media". The question was meant to be, can the affected Macs boot the ISO if it is built with partition_table=off without further modifications? I.e. could the Archiso be fixed by using that option of xorriso? -- nl6720 (talk) 06:43, 29 June 2019 (UTC)
The answer is no. The xorriso command -boot_image partition_table=off would only hamper booting from USB stick. Optical media are supposed to be inspected for an El Torito catalog, which should have an entry for "platform" EFI. I was involved in that discussion on grub-devel. The Mac problem there was that the EFI partition itself contained again a partition table. For some reason two old MacBooks took offense. But this surplus table is not present in Arch ISOs, because its EFI partition image is not made by program "mformat". (We found it in the Guix distro which uses program grub-mkrescue for creating its ISOs.) Scdbackup (talk) 07:07, 29 June 2019 (UTC)