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Old 05-26-2003, 04:49 PM   #1
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Registered: May 2003
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Question Booting from Mylex RAID

Hi people!

I'm lost. I have this fine machine with 2 4.3GB Disks and 3 9.1GB Disks sitting next to me and can't get it to boot.

The two 4.3GB Disks are arranged as mirrored drives and contain a Slackware 9 installation on a ext3-fs which went fine to the point when LILO gets installed. This fails with a simple error message.

So I created a boot-disk with the raid.s kernel. This boots with the command line root=/dev/rd/s0d0p1 ro. The kernel-driver for the DAC960 ist loaded an prints the correct configuration on the console and says it creates the devices /dev/rd/c0d0 and /dev/rd/c0d1. Then the booting continues but stops then with the following error:

VFS: cannot open root device "rd/c0d0" or 00:00
Please append a correct "root=" boot option

So why can't the kernel find the devices, any clues?

One more piece of info, if I boot the raid.s kernel from the CD, I can access both filesystems without any probs.

bye, sascha
Old 05-26-2003, 07:06 PM   #2
Registered: May 2003
Location: Upstate NY, U.S.
Distribution: Slackware
Posts: 248

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I've read that sometimes kernels don't understand the notation /dev/rd/cXdYpZ for the root device and must be handed the hexadecimal notation for the device. The hexadecimal notation consists of four hex digits of which the first two are the major device number, representing the controller, and the last two are the minor device number, representing the disk and partition.

It works like this for a RAID setup like yours:

The major number is 48 decimal, so 30 in hex, plus the controller number. For c0d0p1 the controller number is 0 so the major number would be 30.

The minor number is the disk number multiplied by 8 plus the partition number. So again for c0d0p1 the disk number is 0, multiplied by 8 is still 0, plus the partition number, 1, makes the minor number 01.

So the root line in lilo could be

root=3001 ro

This may or may not be your problem, but it's worth a try.

Last edited by Rodrin; 05-27-2003 at 12:38 AM.
Old 06-02-2003, 01:41 AM   #3
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Registered: May 2003
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Hi Rodrin!

Thanks a lot that did work out! I've never heard before that one can give the device numbers as a root argument, so i learned something too there.

Thanks again for your quick reply!

bye, sascha


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