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Re: booting with grub to /dev/sda



On Mon, 2005-01-03 at 13:51 -0700, Jim Cromie wrote:
> Jeff Vian wrote:
> 
> >On Mon, 2005-01-03 at 12:36 -0700, Jim Cromie wrote:
> >  
> >
> >>Jim Cromie wrote:
> >>
> >>    
> >>
> >>>IOW - its not even seeing /dev/sda, so autocompletes right past that 
> >>>choice.
> >>>ANY IDEA WHY ?
> >>>      
> >>>
> >>solved
> >>writing to someone else almost always helps
> >>- even iff you dont send, ie wait long enough..
> >>
> >>I just added '(hd1)  /dev/sda'  to /boot/grub/device.map,
> >>now it shows up on the grub-console,
> >>testing actual boot next.
> >>
> >>
> >>    
> >>
> Naturally - I spoke too soon.. :-/
> while grub-console sees it,
> it does not on reboot.
> when I edit the boot-config to force it, it tells me drive doesnt exist.
> when I just select that boot-config, it tries, but errs out
> err 21 iirc,
> press anykey to continue...
> then back to boot-config-choice screen
> 
> >One other problem there.
> >
> >Using grub (as you are) presupposes that grub is installed on the boot
> >disk, and that the boot device is able to tell the system to boot from
> >the usb device. It also implies that usb drivers have been loaded to
> >allow this to happen at boot time, before the OS is loaded.
> >
> >  
> >
> Ive always been less than certain about my understanding of grub,
> and for obvious reasons, reluctant to experiment ...
> 
> when you say 'installed on boot disk', I have several ways to interpret 
> that:
> 1. grub-stage1 is in the MBR
> 2. grub 1.5 and 2 are in /boot/grub/  (on FC-3 at least)
> 3. both the above.
> 
> in my case, Ive got extlinux installed to MBR on /dev/sda,
> 

I probably should have been more clear.
By boot disk, I mean the disk that the bios is reading the MBR from (the
boot disk).
On your laptop that would likely be /dev/hda,  on the usb device you
indicate it as /dev/sda.  If you want to use grub for booting from the
usb drive without another drive hosting grub you will likely need to
install grub on the boot sector of /dev/sda

> 
> >If I understand your plans correctly, you want this usb drive to be able
> >to boot standalone.
> >  
> >
> that is the plan.
> 
> >If I am correct, you want the usb drive to be bootable with no other
> >devices in play, and that means BIOS must be able to boot from the usb
> >device.  Grub has no factor in that scenario until after the device is
> >accessed and the boot sector is read.
> >
> >  
> >
> cuz I got extlinux in there, it has no part at all.
> except when I try to boot the laptop (using grub on /dev/hda)
> and targeting /dev/sda as root.  (an interim step toward my end goal)
> 
> ie: this fails
> 
> title Nomad (Debian, kernel 2.6.8-1-386, on USB-drive)
>         root    (hd1,0)
>         kernel  /boot/vmlinuz-2.6.8-1-386 root=/dev/sda1 ro
>         initrd  /boot/initrd.img-2.6.8-1-386
>         boot
> 
> of course, this works:
> 
> title Fedora Core (2.6.9-1.724_FC3)
>         root    (hd0,1)
>         kernel  /boot/vmlinuz-2.6.9-1.724_FC3 ro root=LABEL=/
>         initrd  /boot/initrd-2.6.9-1.724_FC3.img
> 
> 
> Thanks for reading between the lines here..
> 
> 
> Also, might as well answer Stuart here too.
> 
> the BIOS apparently does see the drive - sort of.
> if I hit escape on the sony splash screen,
> I get an ascii dialog box with 'Removable media' (or similar) as 1st choice.
> But it doesnt actually boot -
> it gives up instantly, and back to grub on /dev/hda
> 
That message may also indicate the cdrom.  Check the BIOS and see if you
can set USB as a boot option.  Some of the newer boards/BIOSes can do
that.    If the bios can boot from USB you are most of the way there.


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