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Re: Command extension suggestions


From: Marco Gerards
Subject: Re: Command extension suggestions
Date: Thu, 14 Jun 2007 12:49:26 +0200
User-agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux)

Bean <address@hidden> writes:

> On Thu, Jun 14, 2007 at 11:42:24AM +0200, Marco Gerards wrote:
>> Bean <address@hidden> writes:
>> 
>> [...]
>> 
>> >> That sounds much cleaner IMHO.  But IIRC (md) is already in use by the
>> >> RAID/LVM stuff ?
>> >> 
>> >
>> > Maybe (mem) ?
>> 
>> When would this be useful?
>
> You can use it to dump physical memory, for example,
>
> od (mem)+2
>
> dump first 1K of memory
>
> od --skip-bytes=0x413 --read-bytes=2 (mem)
>
> dump the word at 0x413.
>
> I can't think of other use at the moment.

Right, so mainly debugging :)
 
>> > Also, I don't know if GRUB2 kernel support initrd. You can start grub4dos
>> > like this:
>> >
>> > kernel /grub.exe
>> > initrd /aa.img
>> >
>> > Inside grub4dos, the initrd can be access using (rd). It would be nice if
>> > grub2 support this kind of usage.
>> 
>> You can use the loopback command to do this, if you want to access a
>> filesystem image.
>> 
>> loopback (loop) /foo/bar.img
>> ls -l (loop)/
>
> Initrd can still be useful. In some case, it's not easy to access the boot
> media, such as, cdrom or pxe. To boot from such media, you can either put
> everything in core.img, or you can create a minimum core.img, and put other
> files, like *.mod, grub.cfg, font, etc, in an initrd. The initrd can be
> loaded along with core.img, using loader such as isolinux or pxelinux.

Well, I see the problem but I do not agree with the solution.

The problem for GRUB 2 is that initrd is very linux specific.  It's
part of a loader.  Perhaps we either have to extend loopback to load a
file into memory on beforehand.  Or add a memdisk disk or so.

One problem with initrd is that it is very architecture specific.
Another problem is that the initrd is unloaded when you load another
kernel or OS.  Besides that, reusing initrd appears hackish to me :-).

--
Marco






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