Bug#672104: ITP: pv-grub-menu.lst
Le Fri, May 11, 2012 at 04:17:39PM +0100, Ian Campbell a écrit :
>
> Can I just check I understand the motivation for this script properly.
>
> There are two ways of setting up the disk for a VM.
>
> The first is the "whole disk" scheme. In this configuration the VM
> configuration contains the entire "xvda" which contains a partition
> table in the usual way. In this configuration either grub-legacy or
> grub-pc can be installed and "grub-install /dev/xvda" does the right
> thing including setting up the MBR. This is useful because you can flip
> quite easily from PV to HVM just by changing the VM config and
> rebooting. (This is the setup I generally use myself, so I'm mostly
> familiar with it)
>
> The second scheme is the "split partitions" scheme. In this
> configuration the VM config contains "xvda1" and "xvda2" etc which
> appear to the guest OS as partitions but critically there is no overall
> "xvda" and therefore no partition table. This means that "grub-install"
> cannot work. This is the configuration which EC2 etc use and therefore
> this update-grub variant is necessary.
>
> Is that right?
Exactly.
When installing Debian on a EC2 volume with Debian Installer, the partition is
a "whole disk", completely usable by grub. But that means that when the newly
prepared Debian system is booted, it is a root partition, which is "split
partitions" in the Amazon cloud and grub hooks will fail when installing a new
kernel (I did not have time to triplecheck). Perhaps that could be solved by
making the hooks checking for the availability of a MBR before running grub,
but the grub packages are quite critical, and I am not sure how this additional
complexity would be welcome. In addition there is a second problem.
Pv-grub needs a menu.lst file that is made by GRUB 1. But Debian's GRUB 1
package is in maintainance-only mode, I do not know what are the plans to
remove it eventually, but once GRUB 2 can replace it in all cases, this may
happen. So it is probably better to have a menu.lst-builder script for
pv-grub maintained somewhere else. The pkg-xen project on Alioth is a good
idea indeed.
Or maybe pv-grub could be extended to parse menu.cfg files ? But I do not
know how long it would take for this new function to propagate to Amazon.
Have a nice day,
--
Charles Plessy
Tsurumi, Kanagawa, Japan
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