Re: Grub-install documentation or override?

[Andrei Borzenkov]

В Fri, 26 Jun 2015 17:03:27 +0000
<address@hidden> пишет:

> > > 
> > > It does not appear libdevmapper is a part of LFS.
> > 
> > Then no kpartx would be possible at all. Where do you think /dev/mapper
> > devices come from?
> >
> 
> 
> I think you misunderstood.
> kpartx is run from the host Debian system. It has the mapper but does not 
> have grub. The LFS system has grub, but does not have libdevmapper.

Then use host Debian system to install grub. Why do you insist on doing
it in chroot?

But I find it really hard to believe that any Linux distribution would
not include LVM.

> 
> 
> 
> >  I could be wrong, but I don't see it anywhere.
> > > 
> > > I don't understand why grub-install needs to find the partition 
> > > /dev/mapper/loop0p1 at all. Surely all it needs to do is install to the 
> > > MBR of /dev/loop0 and the embedded space before the first partition. Why 
> > > would it need anything other than the device name /dev/loop0 ?
> > > 
> > 
> > Because it needs to know which drivers are requires to access $prefix;
> > whether $prefix is on the same drive as primary boot sector; which
> > partition $prefix is in; etc etc etc
> > 
> 
> I'm not sure exactly what you are referring to with $prefix.

Which is exactly why grub-install exist - to make it unnecessary for
users to know what $prefix is and how to access it.

> Is there no way to manually tell grub that information, rather than have it 
> try (unsuccessfully) to auto-detect it?
> There should always be a way to manually override any kind of auto-detection 
> logic, IMHO.
> 

There is - to the extent. It is possible to use grub-mkimage and
grub-bios-setup directly. But that also means you will be duplicating
grub-install logic and need to know all low level details.


> 
> > > Assuming libdevmapper is not an option, how could I bypass grub-install, 
> > > also assuming my /boot/grub directory is empty at start?
> > 
> > Try partitioned loop - losetup -P ...
> 
> 
> I've never heard of that option. I will see if it works.
>