Re: Switching to another boot device on failure

[Venkata Subbarao <rao.subba.venkata@gmail.com>]

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I purposefully modified grub.cfg and changed the UUID in the line starts
with "linux /boot/vmlinuz...... root=UUID=XXXX"
Ended up in the (initramfs) prompt because such partition is not present.
Hence, I was thinking of checking CRC.

Thanks and Regards,
Subbarao

On Thu, Nov 20, 2014 at 10:53 PM, Andrei Borzenkov <arvidjaar@gmail.com>
wrote:

> В Thu, 20 Nov 2014 19:08:10 +0530
> Venkata Subbarao <rao.subba.venkata@gmail.com> пишет:
>
> > Once again Thank you Andrei.
> > Modified the grub source and added grub_exit (). After this BIOS booted
> > from next device.
> >
> > I am now working on a solution where if the UUID present in the grub.cfg
> > goes bad.
> > One way I am thinking is to check the CRC of the grub.cfg and other image
> > files required for booting. This may be bit lengthy.
> > Let me know if you have suggestions.
> >
>
> grub supports automatic signature verification for files; in case of
> mismatch file open fails. Does it help?
>
> > Thanks,
> > Subbarao
> >
> > On Wed, Nov 19, 2014 at 8:57 AM, Venkata Subbarao <
> > rao.subba.venkata@gmail.com> wrote:
> >
> > > Thank you very much Andrei.
> > > I will try out this and update.
> > >
> > >
> > > - Subbarao
> > >
> > > On Wed, Nov 19, 2014 at 8:46 AM, Andrei Borzenkov <arvidjaar@gmail.com
> >
> > > wrote:
> > >
> > >> В Tue, 18 Nov 2014 10:51:00 +0000 (UTC)
> > >> Venkata Subbarao <rao.subba.venkata@gmail.com> пишет:
> > >>
> > >> > Hi All,
> > >> >
> > >> > I am working on a task on XUbuntu OS in which due to any reason if
> > >> booting
> > >> > fails I would like to switch to another boot device by zeroing the
> MBR
> > >> of
> > >> > current boot disk. Is this possible ?
> > >> >
> > >> > For example instead of showing following prompt, I would like to
> zero
> > >> out
> > >> > the MBR so that the BIOS can select next boot device upon reset.
> > >> >
> > >> > error: no such partition
> > >> > grub rescue>
> > >> >
> > >>
> > >> grub supports only very limited and controlled ways to write to
> > >> device/file. Doing something like this in unattended manner is
> probably
> > >> way too dangerous.
> > >>
> > >> What would be possible is to optionally exit grub (after timeout) in
> > >> this case; then BIOS should proceed to next boot device.
> > >>
> > >
> > >
>
>

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