Re: Is it possible to simply copy the kernel from one machine to another and use it?
On Tuesday 11 April 2006 02:12 pm, Mark Fletcher wrote:
> --- anoop aryal <aaryal@foresightint.com> wrote:
> > On Friday 07 April 2006 02:39 pm, Yu,Glen [Ontario]
> >
> > wrote:
> > > Hello everyone,
> > >
> > > I was wondering if it's possible to copy the
> >
> > vmlinuz-x.y.z from one machine
> >
> > > to another and have the other machine run properly
> >
> > with it. Here's the
> >
> > > scenario:
> > >
> > > I have 2 systems, both running Debian 3.1 (Sarge),
> >
> > and their hardware is a
> >
> > > little different from each other. Suppose my
> >
> > machine is running a 2.4.x
> >
> > > kernel and the other a 2.6.x kernel, can I simply
> >
> > copy the
> >
> > > /boot/vmlinuz-2.6.x kernel over to my machine's
> >
> > /boot directory, make the
> >
> > > appropriate changes to /boot/grub/menu.lst and
> >
> > have it work as if I had
> >
> > > installed it through apt or dpkg?
> > >
> > > If anyone has actually tried this and got their
> >
> > machines to work, I would
> >
> > > like to know what and how you did it.
> >
> > i am in the process of doing it to a machine where i
> > had to use debootstrap to
> > install the system from an ide drive to a scsi drive
> > (long story).
> >
> > it is pretty easy to get it to work as long as the
> > root filesystem on both
> > machine reside on similar hardware
> > (best-case/simplest-case scenario is both
> > machines use IDE drives to boot). if that's the
> > case, copy the kernel, the
> > modules directory (look in /lib/modules/), the
> > initrd file and you should be
> > set.
> >
> > if the root fs resides on dissimilar hardware (eg.
> > one has IDE and another
> > machine has SCSI or even different SCSI cards etc..)
> > then you'll need to fix
> > your initrd to load the correct modules (or
> > recompile the kernel to inline
> > all needed modules). while this is doable, it is
> > slightly more complicated to
> > give a generic howto. google cramfs and initrd and
> > you should find some
> > discussion on the subject.
> >
> > > Thanks,
> > > -Glen
>
> ----------------------------------------------------------------------
>
> > > Glen Yu | 416-739-4861 | glen.yu@ec.gc.ca
>
> ----------------------------------------------------------------------
>
> > --
> >
> >
> > anoop aryal
> > aaryal@foresightint.com
> >
> >
> > --
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>
> Bear in mind if you do this, your target machine will
> have to have hardware that's at least similar enough
> to your source machine's hardware that the correct
> drivers will be available, either compiled in as
> modules or built into the kernel. If the kernel you
> wish to copy is a stock kernel, then you are more
> likely to get away with this on dissimilar hardware
> than if you built your own -- but then if it's a stock
> kernel, just dpkg it on the target machine!!!
>
> Also your target machine will need to have the same or
> better CPU to avoid CPU instruction-set assumptions in
> the source kernel causing weird effects on the
> lower-spec target machine.
>
> If your hardware is wildly different then this is
> going to be troublesome.
>
> In general it's better to build your kernel on the
> machine you intend to use it on, or at least on a
> machine that's so close in spec it might as well be
> the same machine. Failing that, use a stock kernel
> that's been put together by Debian kernel packaging
> folks who Know What They Are Doing (TM). These are
> designed to run on a wide variety of hardware.
good advice. i wish they would also package a kernel for HIGHMEM > 4G. that's
been the only reason i've had to compile my own. i don't mind having to
compile *all* the modules (as in the default stock kernel). as the whole
thing blows by pretty quick on the machines i have to do it on anyway. in
fact, i take the stock config, change the memory limit and compile away.
but most of the machines i have to do this for are from the same vendor (same
arch, CPU etc..) and only differ in components like the RAID controller etc.
so i typically build the initrd with all the modules i need and then i can
use the same kernel package for all the machines.
>
> Assuming you're still set on doing it -- if it's a
> stock kernel dpkg the .deb file on your target machine
> instead of copying over. If it's not and you still
> have the source tree you built the kernel from
> originally, then use make-kpkg to build your kernel
> image and modules into a .deb file on your source
> machine and then dpkg THAT on the target machine. If
> you don't still have the sources, you need to copy the
> kernel image in /boot, and the modules for this kernel
> from /etc, and you probably need to do something to
> System.map in /boot as well but I'm not sure what
> you'd need to do there. Best of luck...
>
> Mark
--
anoop aryal
aaryal@foresightint.com
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