Re: Booting from offset

[Andrei Borzenkov]

18.05.2016 21:10, Diddier Hilarion пишет:
> Hi, the problem is the following.
> I have a hard disk with the first sector physically damaged (read or write
> is not possible so there is not partition table), I would like to know if
> it's possible to specify the root as the block device + an offset in which
> is the partition. Something like this:
> 
> menuentry myos{
>     ...
>     set root=(hd0)+102400
>     ...
> }
> 

No. "root" refers to device, which is "hd0" in this case. "(hd0)+102400"
is file name and cannot be used for it.

What you could try is to create loopback device, like

loopback loop0 (hd0)102400+12345678
set root=loop0

where `12345671 above is exact block count from the offset 102400. You
can then use loop0 like any other device in grub except of course it
won't be known to a program you boot with grub.

You cannot omit block count currently.

> Where 102400 is the offset in any unit (sectors or bytes).
> 
> I've seen this behavior to specify files in a filesystem but the
> documentation talks nothing about specify a partition in this way.
> 
> ofcourse grub will be installed in a second block device.
> 
> Thanks in advance.
> 
> 
> 
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