[Beowulf] cloning issue, hidden module dependency
tjrc at sanger.ac.uk
Tue Dec 9 04:07:14 EST 2008
On 8 Dec 2008, at 11:15 pm, David Mathog wrote:
> Bogdan Costescu wrote:
>> Having a monolithic kernel that "just works" on a large variety of
>> hardware means answering "y" to most drivers; the kernel itself would
>> then grow as large as the "immense initrd" that you mention.
> I don't think so. It only has to work with a large variety of disks,
> at that, not necessarily at optimal speeds. Basically it just has to
> function well enough to access the OS files on disk, where the rest of
> the modules are, so that those drivers can be loaded later. The boot
> kernel need not have every video, network, etc. driver in it.
> In any case, the sizes of the vmlinuz/initrd files discussed so far
> Distro Kernel vmlinuz initrd Kernel has IDE builtin
> Mandriva 2007.1 (188.8.131.52) 1607583 357892 Y
> Mandriva 2008.1 (184.108.40.206) 1787352 2214302 N
> Ubuntu 8.04.1 (220.127.116.11) 1903448 7906356 N
> Sure this is apples and oranges, but to me it looks like taking the
> stuff (and maybe other drivers) out of the boot kernel is resulting
> in larger and larger initrd files, with the size of initrd going up
> faster than the size of vmlinuz, by a lot.
Ubuntu put quite a lot of other stuff into the initrd which has
nothing to do with device drivers. For example, the initrd includes
casper and all its support scripts, which provide support for things
like persistent USB storage when running as a Live CD.
But they also do put the entire kitchen sink in there in terms of
device drivers; Ubuntu does aim to cover as wide as possible a range
of possible hardware. It's very easy to build a custom kernel package
with just what you want using the 'make-kpkg' command, and then you
can strip out all the extraneous cruft if you want (I never bother -
it's only modules that don't get loaded, and the only performance
issue would be if you're PXE booting)
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