Re: [PLUG] device IDs on boot

[Kevin Brosius <kbrosius@kns.com>]

I'd probably go with what the boot messages tell you on your machine. 
Most disk device drivers print out the devices they find during the boot
process.  Also, most disto installers will let you change to another
text console to view the log files or dmesg.  So, after RH boots, try
out Alt-F1,F2, etc until you get a prompt, then look at 'dmesg | less'
or 'less /var/log/messages' and see what devices are loaded on your
machine for disk drives.  I'd expect an hdX of some kind in your setup,
plus some devices provided by the RAID driver.  For the RAID, it depends
on what the particular driver gives you for devices.

For example, I've used a MYLEX RAID controller.  It has BIOS config for
the logical drives, such that I can configure it for as many logical
drives that Linux can use as I want.  Linux doesn't need any of the
actual hard drive info for the install, just which device the RAID has
configured (the Linux driver uses something like /dev/rd/c0d0p0 for a
logical controller/drive/partition of 0, on up through 200+ devices.)

You'll need to find out how the RAID is setup in your case, or even if
it presents multiple partitions to Linux.  You might be able to tell all
this from the boot messages.  If not, you may need to look at
documentation for the RAID controller or Linux RAID driver it uses.

Kevin


Wayne Dawson wrote:
> 
> I've sometimes wondered how the ids for physical disks are determined in
> Linux.  Now I'm prompted again to wonder, and in this case it makes a
> difference in what I'm doing.  While installing Linux, how do I know which
> device id corresponds to any given physical device?  Choices for a
> particular install I'm doing are:  hda (I think that's the IDE drive, which
> I don't want to install on), sca (a SCSI device I assume), or scb (another
> SCSI device I assume).
> 
> If anyone has a quick explanation of how this works or where I can find it,
> please let me know.
> 
> Thanks,
> Wayne Dawson
> 
> More details for those who are interested:
> I'm trying to install Red Hat to be booted from a RAID.  I'm very new to
> using RAID.
> 
> The RAID is in a separate chassis from the computer I'm using to install
> the OS.  It has a hardware RAID controller (Intel SRCU31LA), and there are
> several hard disks in the RAID chassis.  The computer also has an IDE disk,
> but ultimately this computer will not be used with this RAID (we haven't
> bought the new computer yet).
> 
> In the (text based) Red Hat install program, I was given the following
> options to install onto:  hda, sca, and scb.  Not knowing how these device
> names are determined, I guessed sca was where I wanted to install.  The
> install completed and now I have a system that will not boot without the
> boot floppy (a RAID controller vs OS compatibility issue I suspect), but it
> does indeed require the SCSI chassis to be powered on so apparently the
> bulk of the OS resides there.  However, I'm confused about this because my
> RAID controller claims my RAID HOST has a status of "fail" (It's RAID level
> 5 by the way, with 3 disks).
> 
> Perhaps the disk that is not configured as part of a RAID is available
> through the RAID controller as a standalone disk, and that's what I
> installed the OS on?
>
_________________________________________________________________________
Philadelphia Linux Users Group        --       http://www.phillylinux.org
Announcements - http://lists.netisland.net/mailman/listinfo/plug-announce
General Discussion  --   http://lists.netisland.net/mailman/listinfo/plug