Problem with random disks mount sequence

[Mikkel L. Ellertson]

Daniel B. Thurman wrote:
> 
> Well, I have an old VA Linux Systems 504, and in my case there
> was absolutely nothing I could do to force the Bios/load order
> as it appeared that the drives were being loaded scsi first then
> the IDE drives.
> 
> I had one helluva time trying to install Fedora 8 in this way,
> and I have tried many times to try to get Grub right.  I gave up
> relying on the F8 LiveCD to define the drive order so I basically
> disconnected all of my SCSI and IDE drives sans IDE-0 PM drive.
> 
> I was then able to install F8 LiveCD on the *right* drive and then
> once I got that one drive working, I proceeded to fold in the other
> drives one-by-one and built up each drive/partition so that I was
> able to spread the files around evenly across drives/partitions.
> 
> I did notice in F8-LiveCD that there was this one place in Grub
> Advanced configuration that *seemed* to allow me to change the
> drive order to which I could apply the MBR but the device names
> (sda-sdd) remained the with the physical drive (IDE-SCSI) so that
> did not help much. F8-LiveCD sees drives much *differently* than
> when booting directly off the MBR HD drive itself, or so it seems.
> For example: In F8 LiveCD, it sees drives:
> 
> sda = scsi drive 3
> sdb = scsi drive 4
> sdc = IDE-0 PM
> sdd = IDE-0 PS
> 
> But when I completed installation and booted off the drives directly,
> it sees:
> 
> sda = IDE-0 PM
> sdb = IDE-0 PS
> sdc = scsi drive 3
> sdd = scsi drive 4
> 
> See the "flip"? That is why I had to get the IDE-0 PM drive ALONE during
> install so that when it came to booting off the target boot drive - all the
> other drives fall in proper order.
> 
> Yeah, that was a pain - but I got it to work.  The last update before
> F8 was FC4 - which is why I do not do Fedora installs too often.  Brings
> back very painful memories. ;)
> 
The order the BIOS see drives depends on the BIOS settings. I have
had several systems with a mix a IDE and SCSI drives. If you tell
the system to boot off the SCSI drive, then that is the first BIOS
drive. When you tell it to boot off the IDE drive, then that is hte
first BIOS drive. When booting for a CD, it depends on the BIOS as
to weather the IDE or SCSI drive is the first BIOS drive. Some BIOS
have a setting for this, and other do not. The problem is that after
Linux has booted, there is not way to tell the BIOS order. The
default has been that the IDE drive came first, and if it did not,
then you have to tell the boot loader about it so that it installed
and loaded using the correct drive. (Grub has the device.map file
for this.)

On newer systems, I have run into this when installing to a USB
drive. When you boot from the CD/DVD, the system drive(s) come
before the USB drive, but when you boot from the USB drive, it is
the first BIOS drive. So unless you use advanced configuration,
and/or correct the Grub device.map, things are going to get
installed wrong, and Grub is not going to be able to boot. When
installing Grub, it has to be configured for how the system is going
to look when it boots, regardless of how it looks when it is
installed. If you do not use device labels, you also have to edit
/etc/fstab to match the configuration when booting. (The USB drive
will usually be /dev/sda when booting from the USB drive.)

Mikkel
-- 

  Do not meddle in the affairs of dragons,
for thou art crunchy and taste good with Ketchup!

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