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ZxCv84
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Joined: 13 Jun 2006
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PostPosted: Fri Jul 31, 2009 5:22 am    Post subject: Booting from MDADM Reply with quote

I use a BIOS-based fake RAID. dmraid only messes it up, so I heard that mdadm 3.0 supports Intels software raid so I compiled it from fedora sources and it works.
But I can't get Gentoo (actually Funtoo) to boot from it. Atm Im using GRUB on a separate disk that is not in the raid0 array and it boots the kernel but doesnt mount the root system from the raid. But the plan is to put everything into that raid array if I can figure out how to install grub to it....

But how do I get the kernel to mount the raid array for the root system correctly?

Any suggestions?
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aceFruchtsaft
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PostPosted: Fri Jul 31, 2009 9:44 am    Post subject: Reply with quote

If you build your kernel with genkernel, you can pass it the --dmraid option and it will build dmraid support into the initramfs. You then need to add the dodmraid option to the kernel line in grub.conf.

I've never tried this with dmraid (only with Linux' own MD devices) and don't know whether this works with mdadm 3.0 but you could at least give it a try.
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ZxCv84
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PostPosted: Sat Aug 01, 2009 11:39 am    Post subject: Reply with quote

Yeah I run genkernel with the mdadm flag but is dmraid really required too to run mdadm?

dmraid will just mess up the raid array and I really dont want to start once over again so I try to keep away from it... Dunno if its after mounting or writing but all 3 disks appear offline in the raid after a reboot using dmraid, I've been able to mount them afterwards but BIOS wont no longer give me a boot option for that array.
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NeddySeagoon
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PostPosted: Sat Aug 01, 2009 12:02 pm    Post subject: Reply with quote

ZxCv84,

You also need a patched mdraid_start.sh to be able to start your raid sets.
From this page a new mdadm is not enough. Somehow, you need to get the patched mdraid_start.sh into your initrd as the kernel cannot autostart bios raid sets, there being no partition tables on the component partitions, as there are no component partitions.
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ZxCv84
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PostPosted: Sat Aug 01, 2009 3:07 pm    Post subject: Reply with quote

My initramfs doesnt seem to have mdraid_start.sh or anything called like that, isnt that some Fedora/RH stuff?


Dunno, Im getting tired of this maybe I should just install Fedora and stick with it, Gentoo is getting too close Debian stability anyway. :cry:
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NeddySeagoon
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PostPosted: Sat Aug 01, 2009 6:55 pm    Post subject: Reply with quote

ZxCv84,

Well, you need some way to start your raid array, since you cannot use kernel autodetect.
You may be able to use mdadm and pass it a command line, so then you need mdadm in your initrd.
Note that a genkernel made initrd, does not use the same versions of packages that are installed on your system.

Your will need mdadm-3 in the initrd
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