Troy, Konstantin,
Thank you very much for your quick reply and valuable information.

As suggested, I hope to use extlinux for grub, and sl5.6 for sl5.5. However, I'm currently very mobile (for the next week or so) but will give feedback once I try out the suggestions.

Kind Regards,

William.

--- On Wed, 3/16/11, Konstantin Olchanski <[log in to unmask]> wrote:

> From: Konstantin Olchanski <[log in to unmask]>
> Subject: Re: install the full SL6, SL5.5 OS's and GRUB on external USB hard drive
> To: "Troy Dawson" <[log in to unmask]>
> Cc: "William Shu" <[log in to unmask]>, "[log in to unmask]" <[log in to unmask]>
> Date: Wednesday, March 16, 2011, 5:12 PM
> On Wed, Mar 16, 2011 at 09:45:13AM
> -0500, Troy Dawson wrote:
> > I have a full distro on a USB stick.  It's
> currently Fedora 13 instead 
> > of SL6, but the procedure is the exact same.
> > 
> > Do a normal install with the USB hard drive plugged in
> and selected as 
> > the main hard drive, and with all your partitions on
> it.  The only thing 
> > you have to be careful of is where grub is put, and
> what order grub 
> > thinks the drives are.
> 
> 
> In my experience, trying to USB-boot Linux using SL5 GRUB
> is futile. GRUB gets
> hopelessly confused by the ordering of BIOS "hard drives" -
> which seems to
> change between cold and warm reboots.
> 
> BTW, on the machines where I looked into it, one cannot
> "select USB hard drive
> as the main hard drive" on a permanent basis - if you ever
> boot the machine
> with the USB drive accidentally unplugged or powered down,
> I see BIOS settings
> reverting back to whatever crazy random order you use and
> GRUB will fail
> to boot until you go back to the BIOS setup screen and
> change the settings.
> 
> The best I can tell, the root of the problem is with GRUB
> insisting on booting
> from disk 0 (or whatever number is specified in grub.conf)
> instead of continuing
> to use the boot disk selected by the BIOS (as
> SYSLINUX/EXTLINUX seems to do).
> 
> This strategy of booting from BIOS disk number selected in
> some config file
> may have worked well in the days of hardwired "primary
> master" IDE disks and
> mostly continues to function with hardwired SATA disks
> (i.e. fails on ASUS A8N-E mobos
> where ordering of SATA ports by BIOS and Linux is not the
> same), but completely
> makes no sense with dynamically assigned USB disks (if I
> have 2 USB disks, which
> one is disk 0? Yes, it is in the USB enumeration order, so
> it is deterinistic,
> but if I plug in a 3rd USB disk, USB enumeration order may
> change and GRUB will
> not boot).
> 
> Anyhow, according to http://www.gnu.org/software/grub/ GRUB has
> been abandoned, so why are we still using it?!? In
> contrast, SYSLINUX/EXTLINUX/PXELINUX
> is still in active development. (Yes, there is GRUB-2, if
> you can find it, but SL5 is not
> using it).
> 
> 
> K.O.
> 
> 
> 
> 
> 
> > 
> > http://www.scientificlinux.org/distributions/6x/installing/boot.loader.configuration.html
> > 
> > On SL6, be sure to select "Change device" and make
> sure your USB drive 
> > is marked as the "First BIOS drive".  Then make
> sure it's set to install 
> > the boot loader on the MBR of our USB hard drive.
> > http://www.scientificlinux.org/distributions/6x/installing/large/boot.loader.5.png
> 
> 
> 
> -- 
> Konstantin Olchanski
> Data Acquisition Systems: The Bytes Must Flow!
> Email: olchansk-at-triumf-dot-ca
> Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C.,
> V6T 2A3, Canada
>