Gentoo on amd64 and software Raid

Dark Mayu · n00b Joined: 21 Nov 2009 Posts: 2

Hi there,

I'm new to Gentoo and would love to try this dist. out(and learn new things about linux), but I have a very annoying and depressing problem within the installation process:

I want to install Gentoo mainly on Raid 0. For the setup, I'm using the quick insallation guide, the only difference in setup is my partitioning plan:

sda + sdb, each about 82GB

sda1 & sdb1 for /boot, raid1

sda2 & sdb2 as swap, striped

sda3 & sdb3 as / , striped

Except for the partitions, I did exactly what the Tutorial said. I even tried the howto on the Gentoo wiki.

Now, the installation works up to that point where I have to reboot, right after selecting "gentoo" in grub for boot, the system seems to load, but stops and prints an error saying that it couldn't find root on (hd0,0). It lists sda and sda1 as possible options for root= and just hangs up.

Judging from the actual error, I would guess that the system is not able to read the striped partition... Or did I miss something out not listed in the tutorial?

erik258 · Posted: Sun Nov 22, 2009 2:39 am Post subject:

Well, grub sure can't read a striped partition, and (hd0,0) is a grub disk identifier so I assume grub is the one having a problem.

This site: http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2-quickinstall.xml explains how to use raid and lvm, but you should be able to ignore the lvm parts if you have sufficient understanding of raid. Don't misunderstand me, I don't think you should reinstall, but I think you may have missed something important. Did you install the raid utilities? Is mdadm available in your chroot?

Now, if I misunderstand, you might actually be getting the kernel to boot, in which case you don't have to mess with grub and your boot partition at all, since it's done its job by the time the kernel boots. Instead, direct your attention to your kernel configuration. Did you enable raid? It will have to be compiled in since you can't load a module without the filesystem it's on (unless you're using an initrd or initramfs, in which case you could have a module, but no real purpose to it. you'll always need raid on if you have a root filesystem on raid).

If you need more help, throw up your kernel command line parameters from grub too, would you? I'd like to see whether you're passing root=/dev/md2 (i think that would be right looking at your list).

And also, there's not much point to adding the overhead of software raid for swap space

cubchai · n00b Joined: 11 Sep 2004 Posts: 70

I had this problem too but too bad I have forgotten the solution partially.

I think the problem lies within setting up grub. That's how I solved this problem. You might specify the wrong root for grub.

aguettinger · Tux's lil' helper Joined: 26 Sep 2003 Posts: 84

@erik: if you read Mayu's post again he is exactly following the guide you suggested.

@mayu: It wasn't quite clear if you use LVM or not as in the guide. Can you clarify?
Can you post grub.conf and your /etc/fstab.
Also check your kernel config. Did you set everything as in the guide? Did you enable the stuff for the filesystems you are using (ext2, ext3) and for the disks you are using (Serial Ata drivers).

Also, in the guide / is raid-1, not stripped.
_________________
regards
- andy

Dark Mayu · n00b Joined: 21 Nov 2009 Posts: 2

Thanks for your replies.

@aguettinger:
the only difference between the guides configuration and my one is that I use raid 0 for / and no lvm at all.

@erik258:
I'm not sure if Grub is the problem since I am able too boot into it and also can configure it. But if I select Gentoo to boot, it stops at the point where it's supposed to mount / .

Yes, the 2 hdd I use are 2 old Server SATA drives. I have another hdd which serves as backup drive.

I am sorry for not giving many detailed informations, the problem (and this is also the reason why I have to reinstall all the time) is that if I boot the minimal cd, the md partitions are not available anymore.
cat /proc/mdstat doesn't list anything, thus I need to start from scratch again.

fstab looks like this:

erik258 · Posted: Sun Nov 22, 2009 6:27 pm Post subject:

networkorg · n00b Joined: 02 Feb 2006 Posts: 74 Location: Buenos Aires

Hi,

I am not sure if you have still solved your problem. But this info should help to fix the boot sequence as I have it in an enviroment system. First is to change the kernel line in your grub.conf (only one examble) :