[CentOS] install detecting disk as sdb not sda

Sat Feb 4 18:06:58 UTC 2012
David G. Miller <dave at davenjudy.org>

wwp <subscript at ...> writes:

> 
> Hello Ross,
> 
> On Fri, 3 Feb 2012 16:01:53 -0500 Ross Walker <rswwalker at ...> wrote:
> 
> > On Feb 3, 2012, at 1:34 PM, wwp <subscript at ...> wrote:
> > 
> > > Hello Jerry,
> > > 
> > > 
> > > On Fri, 03 Feb 2012 12:24:14 -0500 Jerry Geis <geisj at ...> wrote:
> > > 
> > >> I am trying to install 6.2 on a machine.
<snip>
> > >> Doing " dmesg | grep sda" does say SCSI removable disk.
> > >> 
> > >> So how can I tell linux to NOT include that when installing?
> > > 
<snip>
> > 
> > You can try disabling USB disk support in the bios.
> 
> Right, but I can't make such settings permanent, as I need to boot from
> a USB disk from time to time, thus, entering BIOS and changing settings
> costs more than unplugging stuff .
> 
> An aspect of the problem w/ that behaviour change introduced w/ recent
> kernel updates, is that some mount mapping tables (fstab for instance)
> are broken if they rely on mount order (sda, hda, etc.) instead of
> device ID or label.
> 
> Regards,
> 
This seems to be BIOS dependent.  I use an external USB hard disk as my portable
computer.  On my personal laptop the external drive shows up as /dev/sdb even if
I boot from the external.  If I recall correctly, it's /dev/sda on my work
laptop.  Doing mounts using UUIDs means everything "just works" regardless of
drive lettering.

Bottom line is play with the BIOS settings.  You may find a combination that
gets you the right drive letters and lets you boot from the USB when you need
to.  On the other hand, my personal laptop BIOS "forgets" about the boot from
external USB drive if I boot with the drive not present.  I have to go into the
BIOS and reset to boot from external the next time I try to use it.

Cheers,
Dave