Re: [gentoo-user] Grub2 boot problem

[Tom H]

On Mon, Feb 5, 2018 at 4:00 PM, Magnus Johansson <gentoo@×××.se> wrote:
>>>
>>> I've got a fresh Gentoo installation that does not boot. I just end up in
>>> the Grub2 shell.
>>>
>>> However when there if I do 'set root=(md/0)' and 'configfile /grub/grub.cfg'
>>> I do get to the Grub2 menu where Gentoo boots just fine.
>>>
>>> /boot and / are both on mdadm devices.
>>>
>>> I've tried re-running grub-mkconfig and grub-install several times without
>>> luck.
>>>
>>> I've added domdadm to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub.
>>>
>>> Drives sda/sdb use GPT disklabels and have 20M BIOS boot partitions first.
>>
>> To which device are you installing grub?
>>
>> Check what "core.img" prefix and modules grub-install is using with
>>
>> grub-install --debug $your_device 2>&1 | grep grub-mkimage
>>
>> [I hit a similar problem with mdadm 6 or 7 years ago and had to create
>> a custom "core.img" to boot normally. You might have to do the same
>> but i would've thought that this problem's been solved. I haven't
>> encountered it since.]
>
> I install grub to devices sda and sdb in the hope I can boot from both/either
>
> m / # grub-install --debug /dev/sda 2>&1 | grep grub-mkimage
> grub-install: info: grub-mkimage --directory '/usr/lib/grub/i386-pc'
> --prefix '(mduuid/46488b259685a3b9c52b7449d592dc80)/grub' --output
> '/boot/grub/i386-pc/core.img' --format 'i386-pc' --compression 'auto'
> 'ext2' 'part_gpt' 'part_gpt' 'diskfilter' 'mdraid1x' 'biosdisk'
> m / #

[ I assume that "46488b259685a3b9c52b7449d592dc80" is the UUID that's
displayed as "UUID" or "Array UUID" when you use "mdadm -D ..." or
"mdadm -E ..." respectively ]

Does "set" in the grub shell display
"prefix=(mduuid/46488b259685a3b9c52b7449d592dc80)/grub" and
"root=(mduuid/46488b259685a3b9c52b7449d592dc80)"?

Does "grub-probe -t drive -d /dev/md0" output "(mduuid/...)" or
"(md/0)" or "(md0)"?