CentOS - Dec 2005 - Booting from an external USB drive?

Is it possible?

Booting the installer from the CD works, finds the USB drive, and
allows me to put the root filesystem on it.  I put the /boot partition
on the internal hard drive and installed GRUB in the boot record of
that partition.

GRUB shows the menu and begins booting, but eventually fails with the
error that /dev/sda5 (the external partition) does not exist.

I was hoping (perhaps in vain) that initrd would provide the necessary
modules/hooks to mount the USB device.  Is there some step of the
installation that I'm missing, or something extra that I need to do by
hand, like in the old days when LILO had to be explicitly told about
SCSI cards?

Bart Schaefer wrote:
> Is it possible?
> 
> Booting the installer from the CD works, finds the USB drive, and
> allows me to put the root filesystem on it.  I put the /boot partition
> on the internal hard drive and installed GRUB in the boot record of
> that partition.
> 
> GRUB shows the menu and begins booting, but eventually fails with the
> error that /dev/sda5 (the external partition) does not exist.
> 
> I was hoping (perhaps in vain) that initrd would provide the necessary
> modules/hooks to mount the USB device.  Is there some step of the
> installation that I'm missing, or something extra that I need to do by
> hand, like in the old days when LILO had to be explicitly told about
> SCSI cards?
My guess is that you will need to manually add the various usb and scsi 
drivers to the initrd image. You might even have to mount /proc/bus/usb 
at the initrd stage. Also check the initrd creates the necessary device 
files for your drive

James Pearson

Bart Schaefer wrote:
>Is it possible?
>
>Booting the installer from the CD works, finds the USB drive, and
>allows me to put the root filesystem on it.  I put the /boot partition
>on the internal hard drive and installed GRUB in the boot record of
>that partition.
>
>GRUB shows the menu and begins booting, but eventually fails with the
>error that /dev/sda5 (the external partition) does not exist.
>
>I was hoping (perhaps in vain) that initrd would provide the necessary
>modules/hooks to mount the USB device.  Is there some step of the
>installation that I'm missing, or something extra that I need to do by
>hand, like in the old days when LILO had to be explicitly told about
>SCSI cards?
>_______________________________________________
>CentOS mailing list
>CentOS at centos.org
>http://lists.centos.org/mailman/listinfo/centos
>  
>
J Austin has a detailed PDF document http://www.vigla.eclipse.co.uk/ 
about Fedora Core Installation to an External USB Disk Drive 
<http://www.vigla.eclipse.co.uk/usb_install.pdf>. To summarize : 
install, reboot in rescue mode and create a initrd with the USB modules :

mkinitrd ??preload=ehci?hcd ??preload=usb?storage ??preload=scsi_mod \
??preload=sd_mod /boot/initrd_usb.gz 2.6.9?xx

Since 'modprobe usb?storage' does not wait for the USB drive to come up,
you may need to add a '_sleep 5_' in the linuxrc script of initrd as 
explain on Simon Ilyushchenko <mailto:simonf at simonf.com> page : 
http://simonf.com/usb/#older.


-- 
Pierre-Francois Honore

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