On upgrading [Re: FC3rc5]

[Per Bjornsson]

On Fri, 2004-10-29 at 17:44 -0400, Jeff Spaleta wrote:
> > I will point you to the fedora core list of objectives, for
> > reassurance that smooth upgrades from core release to core release is
> > considered important as a matter of fedora core policy.
<snip>
On Fri, 2004-10-29 at 15:06, Kim Lux wrote:
> Here is the rub: several times over the last few days people have come
> on to the site and asked if they could update from FC2 to FC3T3 and then
> to FC3 Final without "repercussions".  Nobody has come out and said
> "yes".  I question why nobody is saying yes ?  Are we not sure that our
> upgrade process replaces everything ?  Are we not sure how it handles
> already installed config files ?  Shouldn't an upgrade be an upgrade no
> matter where it starts from ?

Well, that's almost true, but there is a fundamental difference between
upgrading from a stable release to a new release (be it stable or test)
and upgrading from Rawhide or a test release to a stable release. The
difference is that occasionally things slip into rawhide and test
releases that mess up the system in such a way that it's a difficult to
recover.

Just consider the following theoretical situation: Somehow the command
"rm -rf /" gets stuck in the post-uninstall scripts of a package that
hits Rawhide. Oops. It's just not that easy to upgrade from that state,
is it? ;)

Now, Rawhide doesn't contain packages that do stupid things like that,
but that's only because the Red Hat people are too smart to make that
dumb mistake. However, they are not infallible, and but by its nature an
RPM package _can_ have side effects outside of the files owned by the
package. Sometimes the side effects of some change aren't all that
obvious and it might not be all that easy to recover from some packaging
mistakes. The stable releases are tested enough that this kind of goof
generally doesn't slip through, and known thinkos are worked around in
the upgrade process (be it in Anaconda or in the RPM scripts). It's just
not possible to fix things up after every broken package that managed to
hit Rawhide.

Actually, this close to a release nothing that serious should sneak in
so if you install the RC and just update to the final you're very likely
to be in good shape. I actually did that from FC2t2, and it didn't seems
to screw things up that time. But there are really no guarantees.

> I guess my whole thing is that I think the developers and the group
> should take an issue seriously, whether it comes from a fresh install or
> from an upgrade. 

Indeed, and a lot of effort is put into getting upgrades to work.
However, because of the issues with upgrading from broken packages,
issues that only arise when following a Rawhide/test release upgrade
path just aren't practical to deal with.

Cheers,
Per

-- 
Per Bjornsson <perbj at stanford.edu>
Ph.D. Candidate, Department of Applied Physics, Stanford University