Re: no boot

[robert]

On 08/10/2011 10:26 PM, Jordan Uggla wrote:
> On Wed, Aug 10, 2011 at 8:01 PM, robert<address@hidden>  wrote:
> > Ok. Here's the problem.
> >
> > Running a debian-based o/s, in /etc/grub.d/40_custom (set to rwx-r_x-r_x)
> >
> > I have this:
> > #!/bin/sh
> > exec tail -n +3 $0
> > menuentry "Sysrescue" {
> > set root=(hd1,2)
> > linux /sysrcd/rescuecd subdir=sysrcd
> > initrd /sysrcd/initram.igz
> > }
> >
> > then
> > $sudo update-grub
> >
> > well and good. "Sysrescue" shows up in the grub boot menu
> >
> > However, when I select that menu item, I get:
> > error: hd1,2 cannot get C/H/S values
> > error: you need to load the kernel first
> >
> > but, when I  boot to a grub prompt and issue the following commands:
> > grub>set root(hd1,2)
>
> The syntax is "set root=(hd1,2)" not "set root(hd1,2)" (not to mention
> that it's more reliable to search by UUID). This could be the source
> of the difference between executing the menu entry and using the grub
> shell (by having a typo that causes $root not to be changed you are
> likely allowing it to keep its current value, which is likely the
> correct one and "(hd1,2)" is incorrect). Even if that is not the exact
> difference you are almost certainly typing something different at the
> grub shell compared to what is in your grub.cfg as there should be no
> difference in the way they these lines would be interpreted (other
> than needing to run "boot" explicitly at the grub shell).
>
> > grub>linux /sysrcd/rescuecd subdir=sysrcd
> > grub>initrd /sysrcd/initram.igz
> > grub>boot
> >
> > everything goes swimmingly. machine boots to the requested o/s
> >
> > any suggestions?
> >
> > Thanks in advance.
> >
> > Robert

My previous post set up a hypothetical using hd1,2. I have corrected that to 
reflect the exact parameters of the problem ... so ... hd1,5 it should be.

<<<set root(hd1,5)>>> was a 'typo' in my previous e-mail. I am issuing the 
command correctly. I boot to grub from a thumbdrive and enter:
grub> set root=(hd1,5)
grub> linux /sysrcd/rescuecd subdir=sysrcd
grub> initrd /sysrcd/initram.igz
grub> boot

and THAT works, the machine boots to the requested o/s

however, as mentioned earlier, THE VERY SAME lines in my generated grub menu 
produce:
error: hd1,5 cannot get C/H/S values
error: you need to load the kernel first

Here's a copy-paste of the relevant lines from grub.cfg:

### BEGIN /etc/grub.d/40_custom ###
exec tail -n +3 $0
menuentry "Sysrescue" {
set root=(hd1,5)
linux /sysrcd/rescuecd subdir=sysrcd setkmap=us
initrd /sysrcd/initram.igz
}
### END /etc/grub.d/40_custom ###


/etc/default/grub contains:
#GRUB_DISABLE_LINUX_UUID=true
so apparently update-grub uses UUID. however, grub.cfg DOES NOT contain UUID. 
should I explicitly place UUID in file /etc/grub.d/40_custom?? if so, what is 
the syntax?

any further suggestions?

thanks.
robert