Re: mac-boot suggestion, where can I report?
On Sun, Oct 24, 2021 at 09:09:46AM +0200, Thomas Schmitt wrote:
> Hi,
>
> > there a better source to report suggestions for mac builds? (intel x86)
>
> The debian-cd mailing list is in charge of the installation ISOs.
> https://lists.debian.org/debian-cd/
> There is also the debian-live mailing list which is in charge of the
> Debian Live ISOs.
> https://lists.debian.org/debian-live/
Debian CD/DVD team is now the Images team-
https://wiki.debian.org/Teams/DebianCd
[I hang around with them and test releases]
Notably, we do _not_ prepare / maintain the debian-live images which are
made by the debian-live team, although all images are tested when we
make a point release or new major release.
>
>
> > i found out that the debian installer is able to boot in UEFI-mode if I
> > replace the DOSMBR with a GPT header within the usb installer media.
>
> Ubuntu changed to a GPT layout:
>
> $ /sbin/fdisk -l ubuntu-21.10-desktop-amd64.iso
> Disk ubuntu-21.10-desktop-amd64.iso: 2.9 GiB, 3116482560 bytes, 6086880 sectors
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: gpt
> Disk identifier: EF83665C-2F29-48D6-8C3F-80F5A69CFEB7
>
> Device Start End Sectors Size Type
> ubuntu-21.10-desktop-amd64.iso1 64 6077751 6077688 2.9G Microsoft basic da
> ubuntu-21.10-desktop-amd64.iso2 6077752 6086215 8464 4.1M EFI System
> ubuntu-21.10-desktop-amd64.iso3 6086216 6086815 600 300K Microsoft basic da
>
> $ xorriso -indev ubuntu-21.10-desktop-amd64.iso -report_system_area plain
> ...
> System area summary: MBR protective-msdos-label grub2-mbr cyl-align-off GPT
> ISO image size/512 : 6086880
> Partition offset : 16
> MBR heads per cyl : 0
> MBR secs per head : 0
> MBR partition table: N Status Type Start Blocks
> MBR partition : 1 0x00 0xee 1 6086879
> MBR partition : 2 0x80 0x00 0 1
> GPT : N Info
> GPT disk GUID : 5c6683ef292fd6488c3f80f5a69cfeb7
> GPT entry array : 2 248 separated
> GPT lba range : 64 6086816 6086879
> GPT partition name : 1 490053004f003900360036003000
> GPT partname local : 1 ISO9660
> GPT partition GUID : 1 5c6683ef292fd6488c3e80f5a69cfeb7
> GPT type GUID : 1 a2a0d0ebe5b9334487c068b6b72699c7
> GPT partition flags: 1 0x1000000000000001
> GPT start and size : 1 64 6077688
> GPT partition name : 2 41007000700065006e006400650064003200
> GPT partname local : 2 Appended2
> GPT partition GUID : 2 5c6683ef292fd6488c3d80f5a69cfeb7
> GPT type GUID : 2 28732ac11ff8d211ba4b00a0c93ec93b
> GPT partition flags: 2 0x0000000000000000
> GPT start and size : 2 6077752 8464
> GPT partition name : 3 4700610070003100
> GPT partname local : 3 Gap1
> GPT partition GUID : 3 5c6683ef292fd6488c3c80f5a69cfeb7
> GPT type GUID : 3 a2a0d0ebe5b9334487c068b6b72699c7
> GPT partition flags: 3 0x1000000000000001
> GPT start and size : 3 6086216 600
>
>
> > I'm wondering who I can send this suggestion to, as there are mac users who
> > are resorting to the more dangerous hybrid dosmbr+GPT configuration.
>
> Actually only the MBR is valid in Debian ISOs, whereas their GPT is not.
>
> It may be that the GPT debris was initially cruft from Matthew Garrett's
> development of BIOS+EFI ISOs in 2012 (for Fedora).
> Nevertheless this invalid GPT data lure some EFI implementations into
> booting, which would not boot otherwise. So it is not totally useless.
>
> On the other hand there are some legacy BIOS implementations which do no
> consider a USB stick for booting if there is no "boot" flag at some
> MBR partition. But such a flag is not allowed with the Protective MBR
> partition of type 0xee, which announces the presence of the GPT.
> Ubuntu currently adds a dummy MBR partition with type 0, which carries
> the boot flag but is currently ignored by the EFI implementations.
> (No warranty that this will stay so in future.)
>
>
> > there's a mac iso on the debian servers, but I am not sure how I can
> > determine who is in charge of maintaining it.
>
The Mac iso on the Debian servers is for a specific model of early Intel
Macs from about 2007/2008 which had an interesting EFI configuration
such that nothing else would boot on it. There have been other threads
on this in debian-user and certainly debian-cd in the last year or so.
In general, the amd64 netinst or amd64 DVD1 is absolutely fine: I'm
unsure what firmware the Mac requires but if firmware is a problem,
then there is an unofficial image with non-free firmware included [prepared
by the same team - unofficial because non-free is not a part of Debian
and we can't always distribute source/repackage/fix packages we're given and
are reliant on third parties not because the quality is any worse]
https://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/11.1.0+nonfree/amd64/iso-cd/firmware-11.1.0-amd64-netinst.iso
> It gets produced by debian-cd.
> (I think its name is misleading, as it is a BIOS-only image without EFI
> boot lures. Motivated by some Macs, but containing no specific extras
> for Macs.)
>
>
> Have a nice day :)
>
> Thomas
>
Hope this helps. With every good wish, as ever,
Andy Cater
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