Installing Funtoo on a machine with Fake Raid and GPT partition table

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Alexandre Pereira

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Dec 11, 2011, 10:07:59 AM12/11/11
to Funtoo
Hi all,

Currently i installed Funtoo into my Desktop PC.

There were some hurdles i had to overcome, and would like to report
them :

* GRUB2 issues
* Genkernel issues


GRUB2 issues :

Currently with grub2 on funtoo , if i am using dmraid and gpt
partition scheme, grub2 fails to work.
Talking on #grub2 on freenode, advice was given to try the following :
( quoting )

[01:58] <Jordan_U> pereira_alex: I may a a vegue idea of what's wrong.
Either boot the desktop and run "ls" from the rescue shell and tell me
the output, or run "grub-install --modules=part_gpt /dev/mapper/foo --
boot-directory=/path/to/boot/directory/" and try booting again, or
(best) do both.

[02:05] <Jordan_U> phcoder: Do you think it's possible that somehow
grub-probe is thinking that the partition containing /boot/ is
actually a drive, and therefore setting up a cross disk install with
no partmap module much like what happens with (non kpartx) loopback
installs?

After following the advice to include --modules=part_gpt on the grub-
install command line, it installed grub properly.

Note : ( which i still have to test ) It might be possible that this
bug is known, and should be fixed on grub 1.99.


Genkernel issues :

After booting from grub, the initramfs cannot find the device for my
Fake Raid GPT partition.
This is because of one issue that DMRAID does not auto detect GPT
partitions.
I do have the devices on /dev/mapper/ but only the disk, not the
partition.

For this to work , something like what has been done to fedora needs
to be done :
http://git.fedorahosted.org/git/?p=mkinitrd;a=commitdiff;h=b625d07cb873e7c148442dd03c5b43263a20bf12

here it adds support for kpartx discovery of the partitions right
after creating the disks with DMRAID.

so ... i hacked the initrd script on genkernel and added that
support.

But another problem with genkernel is that upon adding multipath
support ( to have kpartx ), it doesnt work.
It fails to copy the necessary libs for kpartx to work, leaving me
with at boot prompt with "missing libudev.so.0" for kpartx.

I managed to solve this i creating an overlay to initramfs with the
necessary libs into it.

So after all this, it works :) it boots.

Summary :

Grub2 issues : 1.98 seems to have a problem with GPT Fake RAID
partitions. Could be solved with Grub2 1.99. Could it be updated ?

Genkernel issues :
Genkernel seems to fail at creating multipath support ( making a
usable kpartx).
Also needs to add to script initrd on initramfs to do a kpartx -a /dev/
mapper/$device after each GPT device discovered.

Thank You

Peter Panther

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Dec 12, 2011, 6:55:05 AM12/12/11
to Funtoo
Hi Alexandre,

i am very pleased to see someone fighting exactly this problem. In
early spring i bought a pci-e revodrive and till now i was'nt able to
use it properly. I strugled for more than 8 month now to find such a
solution and was just close to buy a new motherboard because i thougt
it is because the bios is not managing right the fake-raid-card. It is
a big problem. Not one of 14 live-DVD-Distris/Versions i tried was
able to set the fake-raid up properly so that booting after installing
the system was possible.
Would you please be so kind to pass me some mor hints about your
initrd script and the overlay. That would be great!
cheers pete

Oleg

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Dec 13, 2011, 3:11:25 AM12/13/11
to Funtoo
grub update is in TODO list before New Year (hope so). We will take a
look into dmraid/genkernel issues as well.
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