grub / grub2 conflicts

Steve Clark sclark at
Thu Sep 15 16:15:12 UTC 2011

On 09/15/2011 12:01 PM, Matthew Garrett wrote:
> On Thu, Sep 15, 2011 at 04:56:43PM +0100, Richard W.M. Jones wrote:
>> For grub1 guests, it has turned out not to matter which specific
>> version of grub [as long as it was grub1] was used, as apparently
>> grub-install updates all files needed in /boot/grub as appropriate.
>> Or at least we haven't come across a guest where this hasn't worked
>> (yet -- we could be in for a surprise).
> The most obvious case where it can fail involves grub being effectively
> unmaintained, and so various vendors have extended it in different ways.
> You may end up with valid configuration files for one distribution that
> can't be parsed by the grub for another. The assumption you're making is
> fragile. It's even worse for grub2, since it has a built-in module
> loader. Modules built for one version of grub aren't guaranteed (or even
> really expected) to work when loaded into another.
Hmm... there isn't a version check to prevent this???? Seems sort of fragile.
>> I'm very interested in how to reinstall bootloaders *without* invoking
>> guest code.  Also in how to not break the bootloader when moving or
>> aligning the boot partition, which sometimes happens for reasons we
>> don't understand (but not on all grub1 guests, only on RHEL 5 era
>> grub1).
> You're asking for the impossible. The only supportable bootloader for a
> specific guest is the bootloader that matches the installed OS. If you
> want to support grub2 on Ubuntu, for instance, you'll need Ubuntu's
> grub2 - not Fedora's. The binary interface may have changed between
> them.

Stephen Clark
Sr. Software Engineer III
Phone: 813-579-3200
Fax: 813-882-0209
Email: steve.clark at
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