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Groups > linux.debian.user > #241625 > unrolled thread

mac-boot suggestion, where can I report?

Started bywestlake <westlake2012@videotron.ca>
First post2021-10-24 06:40 +0200
Last post2021-10-24 13:30 +0200
Articles 3 — 3 participants

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  mac-boot suggestion, where can I report? westlake <westlake2012@videotron.ca> - 2021-10-24 06:40 +0200
    Re: mac-boot suggestion, where can I report? "Thomas Schmitt" <scdbackup@gmx.net> - 2021-10-24 09:10 +0200
      Re: mac-boot suggestion, where can I report? "Andrew M.A. Cater" <amacater@einval.com> - 2021-10-24 13:30 +0200

#241625 — mac-boot suggestion, where can I report?

Fromwestlake <westlake2012@videotron.ca>
Date2021-10-24 06:40 +0200
Subjectmac-boot suggestion, where can I report?
Message-ID<DbDsB-5he-3@gated-at.bofh.it>
hi debianers!

there a better source to report suggestions for mac builds? (intel x86)

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.

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.

By being able to boot the installer in UEFI-mode(as opposed to CSM-MBR), 
here I can completely avoid having to use the problematic gptsync...

.. and would like the debian installer to be improved for macs.

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.

I'm thinking I may have sent it to the wrong mailing list, and not sure 
where to look.

thanks

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#241628

From"Thomas Schmitt" <scdbackup@gmx.net>
Date2021-10-24 09:10 +0200
Message-ID<DbFNM-6MH-21@gated-at.bofh.it>
In reply to#241625
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/


> 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.

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

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#241631

From"Andrew M.A. Cater" <amacater@einval.com>
Date2021-10-24 13:30 +0200
Message-ID<DbJRn-HG-1@gated-at.bofh.it>
In reply to#241628
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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