Re: problems booting a fresh install of gentoo

[Pascal Hambourg]

Le 02/12/2019 à 18:59, Marko Horn a écrit :
> i used a own partition for boot and for /root

A separate partition for /root is a mistake. Or do you mean for / ("root") ?

> both lying on a raid10 

Then they are not partitions (/dev/sd*, /dev/nvme*) but RAID arrays 
(/dev/md*).

> The machine starts normally and the grub menu is showing up.
> After 5 second boot starts and hangs with message:
>
> error: unknown file system
> error: try to load the kernel first.
>
> (looks for me grub cant mount  boot & root)

Only boot.

> i did in the grub config =
> GRUB_PRELOAD_MODULES="lvm xfs mdraid09 mdraid1x diskfilter part_gpt 
> part_msdos"
>
> (dunno, if i need all. but some sounded so.)

Preloading modules in the core image is needed only to read /boot/grub, 
not /boot.

> Also generatimg a initramfs with genkernel (...) > did not helped me.

Of course not. This is a GRUB error, not an initramfs error.

> /etc/grub.d/40_custom
>
> menuentry "gentoo linux 5.4.1 Super Horn Kernel" {
> set root=(hd0,2)
            ^^^^^
This is wrong if /boot is a RAID array. It should be (mduuid/<uuid>) or 
(md/<number|name>). Actually, if /boot is in the same filesystem as 
/boot/grub, then root is already set to the proper value.

> Debian installer with doing raid 10 boots well from all partitions 
> metadata 1.2
> How do the do the magic?

Debian runs update-grub (grub-mkconfig) and os-prober to automatically 
generate grub.cfg.