RHEL and FC Kernels

[Dave Jones]

On Fri, Apr 08, 2005 at 08:32:15PM +0100, Andy Hudson wrote:
 > Hi,
 > 
 > This may sound a bit naive, but what are the fundamental differences 
 > between an EL kernel and a fc3 kernel?
 > 
 > I'm expecting someone to say either RTFM or that EL kernels have 
 > specific patches applied to make them more stable than fc3, say.

To use RHEL4 as an example..
That kernel will be 2.6.9 + patches for its lifetime.

For RHEL, we pick and choose which patches we believe are
'must haves' from upstream (based on bugzilla feedback, customer
demand, and sometimes, well, just because). We then take those
patches, and bend them to fit against a 2.6.9 codebase, which sometimes
is a lot of work.  At the same time, we do everything we can to jump
through hoops and maintain interfaces so that third party modules
don't break between two kernel revisions.
It's an insane amount of work.

For Fedora, things are a lot simpler.
We will rebase to a new upstream release as they become available,
to try and remain as close as possible to upstream.
(We get to drop things each time we rebase as we push things
 upstream during stabilisation after a rebase)
so Fedora gets any new upstream features way faster than
RHEL will (Which sometimes isn't such a blessing if the feature
isn't fully baked).

Feature-wise, both streams have more-or-less the same added-Red Hat
patches (Exec-shield etc).  RHEL has a 4g4g -hugemem kernel, but
that's about the only difference.

To give you something of an idea how much things diverge, here's
the current number of patches included against various trees
including some historic trees..

RHL9:     174
Fedora Core 1:     107
Fedora Core 2:      80
Fedora Core 3:      69
Rawhide:      61
RHEL4:     400

Note that as we get newer releases of Fedora, the patchcount
goes down.

		Dave