[techtalk] SCSI/IDE/booting...the other thread

[Brian Sweeney]

Ok, here's a situation I've witnessed but cannot explain, and I'm sure
that's because once again there's a mack-truck sized hole in my Linux
knowledge I'm unaware of. ;-) Here goes:

I have a user with a machine that has a mix of SCSI and IDE devices.  He
claims that initially the machine had both, then for a while they got rid of
IDE, now they're putting a new IDE in (60G).

Now, near as I can tell, lilo has always pointed to the SCSI device, and
therefore it has always been the boot device.  Indeed, the boot info is on a
scsi device, as is the root partition.  I thought, however, that Linux
*ALWAYS* had to boot off the first device present, which if you have an ide
drive on your system, with most bioses it (the ide) will be the first
device.  Yet, this thing had both, and seems to have booted off the SCSI?

I became aware of this after he upgraded the kernel, rebooted the machine
and got "LI".  Being a good user, he of course did not have a boot disk for
the machine before doing this.  So, we booted off a 6.2CD into rescue mode,
mounted the SCSI root partition (there is no separate boot partition),
chrooted to it and ran lilo.  It rebooted just fine (with his old kernel)
off the scsi device with the ide device attached.  I created a boot disk
with the old kernel, and we tested it out; it worked fine.  So at that point
I decided to edit lilo.conf to include the new kernel, and re-installed
lilo.  This time, on reboot, I got the infamous "LI".

Clearly, I have no idea what's going on.

Theories:

1) I'm wrong about the ide/SCSI thing, and I'm getting LI now because he's
got no boot partition and with the addition of this latest kernel the boot
info goes past the 1023 cylinder limit, so lilo's now upset.

2) I'm right about the SCSI/IDE thing, and there's something else spooky
going on.

There's another machine this user has with a mix of IDE and SCSI drives,
same situation, and it too can only boot from the boot floppy we created.

Suggestions?  I'm thinking we just move the /boot information on to the IDE
device and point it to the / partition on the SCSI device, but I'm wondering
if there's some way to get it to boot off the SCSI device even with the ide
present.

-Brian

-----------------------------------------
Brian Sweeney
bsweeney at physics.ucsb.edu

"The life expectancy of an unpatched, default installation of Red Hat 6.2
server is three days. The last time we attempted to confirm this, the system
was compromised in eight hours."
-The Honeynet Project