RE: [Xen-devel] boot loaders for domain != 0

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> > I think you could get most of this functionality by allowing the
> > location of the kernel to be specified as a file within one of the
> > guests virtual disks (assuming dom0 knows how to mount the root file
> > system).
> 
> Except that you really want to be able to update from within the guest
> what kernel is used instead of having to specify it in dom0.  
> That then
> makes the guest almost completely independent on questions of what
> software runs inside it.

You'll still need a config file in domain 0 that says what the 'boot
disk' for the domain is and what virtual ethernet interfaces it gets
etc.
 
> > We could also access a config file within the guest's 
> virtual disk that
> > could be used to override a subset of the config parameters (e.g.
> > command line, kernel image name etc).
> 
> Parsing a grub.conf is easy enough that you're probably just 
> as well off
> reading it from dom0 and parsing it to determine what the 
> right thing to
> boot is.  You can even do it without mounting by using something like
> libext2fs.  Going really all out would then make it so that when you
> first started a guest domain, you'd be presented with a menu to pick
> what you want (based on the boot loader config), just like you would
> with a normal machine.  

Yep, grub.conf wouldn't be a bad config format to use, though it's
obviously not as flexible as ourcurrent config file that enable varibles
etc.

Using libext2fs would be nice from a security POV (it's probably not too
hard to crash Linux getting it to mount a suitably crafted filesystem
structure), but it doesn't help if the client is using XFS or Reiserfs
etc (though I'm not sure Grub supports these anyhow). Perhaps insisting
on an ext3 /boot is OK.

Ian


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