Re: mac-boot suggestion, where can I report?
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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