Re: Installation, Debian 12, iMac G5, USB thumb drive => “Your installation media couldn’t be mounted. “

[John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>]

Hello Joe,

On Fri, 2025-08-29 at 00:41 -0400, Joe Flowers wrote:
> The installation seemed to go OK and finish OK, but on restart,
> the iMac will not boot. I get the Mac icon that means bootable
> media cannot be found.
> 
> I'm guessing maybe I made a partitioning mistake or a partitioning
> quirk or grub?

Yes, indeed. Your partitioning layout is incompatible with Apple PowerMacs.

> Here is my partitioning setup:
> 
> LVM VG vg1, LV lv1 - 398.5 MB Linux device-mapper (linear)
>     #1    398.5 MB    f    ext2    /boot
> LVM VG vg1, LV lv2 - 398.5 MB Linux device-mapper (linear)
>     #1    398.5 MB    f    HFS    /boot/grub
> LVM VG vg1, LV lv3 - 75.2 GB Linux device-mapper (linear)
>     #1    75.2 GB    f    ext4    /
> LVM VG vg1, LV lv4 - 4.0 GB Linux device-mapper (linear)
>     #1    4.0 GB    f    swap    swap
> SCSI2 (0,0,0) (sda) - 80.0 GB ATA WDC WD800J-40GB
>     #1    32.3 kB        Apple  <---------------------------------------- bet this is the problem? I should have deleted this first?

No, that partition is required. You must not delete it.

>     #2    80.0 GB       K    lvm    untitled
>             25.1 kB        FREE SPACE


Your problem is that your partitioning scheme ignores that the firmware
in your iMac requires plain HFS partition for booting and it must be
the second partition after the 32 KB Apple partition.

This means that you cannot just use an LVM setup like this as the firmware
is unable to access the HFS partition this way. You have put your LVM setup
onto a different disk.

And I'm not sure why you created an ext2 partition for /boot. These partitions
were necessary for bootloaders that use blocklists for loading the stage2
bootloader files. That's not the case for GRUB on PowerMac though which accesses
the stage2 bootloader files by reading it directly from the HFS partition.

See: https://web.archive.org/web/20120605171934/https://opensource.apple.com/source/bless/bless-37/README.BOOTING

Adrian

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