Re: Loadlin and Squeeze kernel 2.6.32
On Sun, Jul 15, 2012 at 10:12 AM, Camaleón <noelamac@gmail.com> wrote:
> On Sat, 14 Jul 2012 19:11:41 -0400, Tom H wrote:
>> On Sat, Jul 14, 2012 at 4:14 PM, Camaleón <noelamac@gmail.com> wrote:
>>> Reading from GRUB's legacy documentation¹, I see none listed. However,
>>> GRUB2 manual² does not even mention the possibility of installing GRUB2
>>> into the first boot sector of a partition, maybe something has changed
>>> between the two versions :-?
>>
>> Nothing's changed except that you have to use the "--force" option to
>> install grub2 into a PBR. The drawback, according to grub, is that you
>> have to use block lists rather than use an intermediate step (grub1's
>> stage 1.5 or grub2's core.img) that understands filesystems.
>
> Which, generally speaking, it translates into...? I mean, what are those
> "block lists" and how are they effectively affecting the boot process
> from a user's point of view?
Let's assume that grub1/grub2 have to load "/boot/grub/camaleon" in
order to boot.
If they're using block lists, they'll locate that file as starting on
xxx block of yyy partition.
If they're using an intermediate stage (grub1's stage 1.5 or grub2's
core.img), they'll locate that file by name.
Block lists are supposed to be less reliable/more fragile/(fill in
with the negative flavor that suits you).
> On systems with multiple operating systems in the same hard disk I've
> always found a more dangerous approach to install GRUB (or any other
> bootloader) in the MBR that inside a partition because you completely
> relay on the bootloder capabilities to boot all of the installed systems
> and also the MBR could be always overwritten when you install a Windows
> system.
When multi-booting Linux distributions, there's no problem installing
grub in the MBR. I have a netbook on which quantal, rawhide, and sid
are installed and grub's uninstalled in rawhide and sid and installed
in the MBR via quantal.
When multi-booting Linux and Windows, installing grub in the MBR *can*
be hazardous to your health and that of your box...
>>>> Are you sure about the "generic boot code"?
>>>
>>> Yes :-)
>>>
>>> ***
>>> Write Generic Boot Code to MBR
>>> Replaces the current MBR with generic, operating system independent
>>> code. ***
>>>
>>> Why this option? I can't tell and I don't know (because I have not
>>> directly tested) if there's any difference between choosing this and
>>> installing no bootloader at all. To be sincere, I don't know if by
>>> selecting no bootloader you can boot at all, I mean, directly from your
>>> hard disk with no other helpers :-?
>>
>> Thanks for the info and the links. You've misunderstood me. I didn't say
>> that Linux could boot without a bootloader. I said that I didn't
>> understand the purpose of the "Generic Boot Code" since other
>> distributions don't use it when installing grub to a PBR.
>
> You're right.
>
> Yes, what I should have say is that the difference between a) installing
> GRUB into the first section of a partition or b) installing GRUB into the
> first section of a partition *and* writing generic boot code to MBR is
> unknown to me.
>
> Why does openSUSE provide such option while others no and what kind of
> changes generates? As I said, I don't know, maybe option a) writes
> specific GRUB code into the MBR while option b) uses generic bootstrap
> data. Differences between the two? That a) does not need the bootable
> flag to be present while b) does? Who knows :-?
No worries.
I've done some googling...
1) The generic boot code's the DOS MBR code that
fdisk/fixmbr/bootrec/bootsect writes to the MBR with the right
option(s). The DOS MBR code's less sophisticated that grub's; it
simply loads the partition marked active.
2) OpenSUSE does this because it doesn't believe in installing grub in
the MBR (but its installer allows you to do so).
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