Re: Which partitioning schemes should be supported by GRUB?

[Vladimir 'φ-coder/phcoder' Serbinenko]

On 06/12/2010 06:32 PM, Grégoire Sutre wrote:
> On 06/07/2010 10:46 PM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>
>> There are two parts of this question:
>> 1) Which partition schemes should GRUB be able to read modules and
>> payloads from ? It's platform-indepedent and 2 conditions apply:
>> - Usage. There are OS which are able to boot from such OS and such
>> configuration isn't considered obscure by them.
>> - Non-confusability. The risk of false positive of this partition config
>> which would prevent normal function is small.
>> If at least one condition is met it's worth considering. If both
>> conditions are met it should be supported.
>
> According to these rules, hybrid msdos+gpt partitioning schemes should
> be supported.  Grub should be able to read files from a GPT partition
> even if the protective GPT entry in the MBR is not in the first slot.
> It's also the conclusion of the thread [1], but I admit that this thread
> is two years old.
>
Any "hybrid" cofiguration fails the criteria of non confusability. Let's
consider a following situation:
- I format disk with scheme A and partitions A1, A2, A3
- I get bored and reformat with scheme B and partitios B1, B2, B3, B4.
When I did this filesystem on A2 may stay intact
- I use grub which supposes that it'shybrid system A+B and save_env's to
A2 since it's a valid partition on valid filesystem. But by a bad luck
save_env overlaps with superblock of B3 which becomes corrupted.
When installed grub sees both partitions A and B it makes sense to allow
user to see both of them for recovery purposes but in any case it should
be a recommended config. Desync is way too easy. And currently grub
isn't changed to new partition notation completely. E.g. during startup
prefix is calculated with old syntax and confusing A+B with either A or
B is likely to make user drop into rescue shell
Also save_env should ensure that no dangerous situation exist.
> Grégoire
>
> [1] http://lists.gnu.org/archive/html/grub-devel/2008-09/msg00101.html
>
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-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko

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