Re: Switching to another boot device on failure

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 20.11.2014 15:38, Venkata Subbarao wrote:
> 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.
> 
What is the scenario you want to protect against? checksums are mainly
useful against hardware failure but if hardware is defective the only
way to surely bring it back is to replace failing components.
The most common way for UUID to go unsync is because of software or
operator error and both are likely to recompute checksum or change
actual disk UUID without changing grub.cfg.
> Thanks,
> Subbarao
> 
> On Wed, Nov 19, 2014 at 8:57 AM, Venkata Subbarao
> <address@hidden <mailto:address@hidden>> 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
>     <address@hidden <mailto:address@hidden>> wrote:
> 
>         В Tue, 18 Nov 2014 10:51:00 +0000 (UTC)
>         Venkata Subbarao <address@hidden
>         <mailto:address@hidden>> 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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