Re: [Xen-API] grub/cmdline

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Tue, Nov 21, 2006 at 04:26:52AM +0000, John Levon wrote:

> On Mon, Nov 20, 2006 at 05:54:36PM +0000, Ewan Mellor wrote:
> 
> > vm has two mutually exclusive groups: "pv", and "hvm", with the fields
> > 
> > vm.pv.bootloader
> > vm.pv.entry
> > vm.pv.kernel
> > vm.pv.ramdisk
> > vm.pv.args
> > 
> > vm.hvm.boot
> > 
> > pv means "use the PV domain builder, and pass the entry, kernel, ramdisk, 
> > and
> > args to the specified bootloader".
> > 
> > If bootloader is empty but kernel is specified, then this means take the
> > kernel and ramdisk from domain 0.  Otherwise, bootloader is a path to the
> > bootloading script.
> > 
> > The semantics of entry, kernel, ramdisk, and args are specific to the
> > bootloader in use.  You get given all those options, and it's up to the
> > bootloader to do something sensible, including ignoring some or all of the
> > specified options.
> 
> I think 'entry' needs renaming as it's only really meaningful for a menu.lst
> based method.

What would you want to call it?  I was thinking that if you have a bootloader
with a menu, you'd use entry, and if you didn't, entry would be blank.  Is
there something else that you'd want to use this field for?

> Your description above doesn't cover the case where neither bootloader NOR
> kernel are set. With my changes, this uses the 'default' bootloader (namely
> pygrub). This needs spelling out in the API doc.

I'd intended that this particular case would be a flagged error, and pygrub
would only ever be used if explicitly specified.  I don't have a strong
opinion on that -- we could do it your way if you prefer.

> Also of interest are what do you see if you have a blank 'kernel' line and you
> boot. Do you get back in 'vm.pv.kernel' what pygrub chose for you, or nothing?
> Same for others.
> 
> I'd actually prefer the latter, because it makes sense for what you put in to
> be what you get out, and in the case of 'grubxen' port, it'd be /impossible/
> for the domain to report the kernel chosen back out. This should probably be a
> informative note in the API docs.

Yes, I'd prefer the latter too.  Let's go with that.

Ewan.

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