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Re: [K12OSN] Memory and K12LTSP kernel ?

"Martin Stevens" <stevens chace enfield sch uk> wrote:

Can anyone tell me how much memory the stock kernel will allow you to use ?

If you installed K12LTSP before installing the memory, you'll have a stock
kernel that will access only 4 GB.

Will i have to recompile the kernel for this ?

Nope, instead you should send your memory to me for shrinking, as it's much
too large. <g>

Actually, CD 1 has an RPM for kernel-bigmem-2.4.20-13.9.i686.rpm - that's
the one that is compiled to access up to 64 GB of RAM.

Now, slipping that one underneath the running "smallmem" kernel is a trick
akin to whipping the tablecloth out from under a fully-laden table setting.
It always works on TV, but you're only seeing the twelfth take. Here's what
I would do:

1. Boot from the K12LTSP or Red Hat CD 1 in "rescue mode"

2. When it offers to attempt to mount your existing system partitions off
the hard drive, let it.

3. Log in on a virtual console as root. No password should be required.

4. I'm fairly sure (from memory) that your system will have been mounted
under /mnt/sysimage. Check that to make sure I'm correct. If so, then give
the command

chroot /mnt/sysimage

5. Now, mount the CD-ROM. A regular "mount /mnt/cdrom" might work here - if
it doesn't, then you might have to exit from the chroot'ed environment,
mount it some other way under the recovery image, and then copy the
required image onto the hard drive somewhere.

6. Assuming the mount command worked, then "rpm -ivh
/mnt/cdrom/RedHat/RPMS/kernel-bigmem-2.4.20-13.9.i686.rpm" might install
the new kernel alongside the old one and even update /boot/grub/grub.conf
to let you select it. Alternatively, you might have to do a "rpm -e kernel"
first, to get rid of the old kernel, then do the "rpm -ivh . . .".

7. Before doing anything else, I would check the contents of
/boot/grub/grub.conf and make sure all looks OK.

8. If all OK, exit from the chroot'ed environment, shut down and reboot.
Voila!, as they say.

WARNING: you are dicing with death here. I can conceive of a few points at
which things might not work as I've described, in which case, you're on
your own (I'm off to bed in a little while). You might want to wait a
little while to see if anyone else has anything to add to the procedure
I've described here. I *have* done this kind of thing successfully in the
past - even successfully rebuilt the kernel RPM for a 486 and installed it,
just to prove it can be done - but I'm offering no guarantees, express or
implied, etc. Still, it's easier than reinstalling.


--- Les Bell, RHCE, CISSP

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