initrd help

fusama · n00b Joined: 31 Aug 2005 Posts: 21 Location: USA

So I've been building a new gentoo system using software raid. Of course it doesn't work (or I wouldn't be adking questions). The problem appears to be that md is unable to auto-detect my raid devices. /boot is raid1 so grub can get to it and start the kernel just fine, / is raid10 which is where the failure is. Of course, not having a root filesystem causes the kernel to panic so all the info I have is what I can see on the last monitor-height of output.

From what I've found on the web at some point autodetect was intentionally broken by the devs due to Bad Things that could happen if you mixed and matched drives from different computers that happened to originally be parts of linux software raid arrays. And that the only way to boot is to use a initrd. Great, but I've never done that before. I've looked on the web but the info I've found on initrd's all has to do with writing C code. I should *not* have to write C code (or for that matter copy-paste someone elses from the net) to get a raid array working, and I'm fairly certain that's not necessary. However, I've not found anything more useful on using an initrd.

Could someone please either tell me or point me to directions that tell me step by step what is needed to create and boot using an initrd? What do I need to enable in the kernel? What files do I have to copy where? How do I need to configure Grub? What other steps are necessary to make this work?

Thanks.

FizzyWidget · Posted: Fri Dec 05, 2008 6:42 pm Post subject:

you could try

http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&chap=7

7.d. Alternative: Using genkernel

should make everything you need to make a bootable kernel, unless you want to do it the manual way

fusama · n00b Joined: 31 Aug 2005 Posts: 21 Location: USA

I'd rather not use genkernel considering I've already configured my kernel the way I want it (except for the initrd). Are those my only two choices: genkernel, and writing C code?

NeddySeagoon · Posted: Fri Dec 05, 2008 7:03 pm Post subject:

fusama,

The kernel still starts my raid, made with the now dead raidtools, so its probably not a kernel issue. Although, I do know that as you have discovered, its depreciated.

You can still go the initrd route and there is no C to write.

Maybe you can use some kernel parameters in grub.conf
See /usr/src/linux/Documentation/md.txt
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

fusama · n00b Joined: 31 Aug 2005 Posts: 21 Location: USA

This problem is that my raid was not made with the now dead raidtools, it was made with the newest version of mdadm. I could re-make my array, but I'd really rather not because at this point that's a "wipe the drive and start over" solution. While its good to hear that writing C code isn't necessary to use an initrd, I still don't know how to do it.

How do I use a initrd?

FizzyWidget · Posted: Fri Dec 05, 2008 7:24 pm Post subject:

http://wiki.clug.org.za/wiki/RAID-1_in_a_hurry_with_grub_and_mdadm - near the bottom has a section about grub and what not

NeddySeagoon · Posted: Fri Dec 05, 2008 11:02 pm Post subject:

fusama,

Did you try what /usr/src/linux/Documentation/md.txt suggests ?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

cyrillic · Posted: Sat Dec 06, 2008 1:19 am Post subject: Re: initrd help

Hu · Administrator Joined: 06 Mar 2007 Posts: 21709

tuber · Apprentice Joined: 12 Nov 2004 Posts: 267

Here's an article with some specifics on how to create an initrd: http://www.timesys.com/EmbeddedLinuxCoffeeHouse/Blogs/initial_ram_disks