ensure upgrade paths through fedora to RHEL?

[Patrice Dumas]

Hello,

As a substitute or a complement to something similar with fedora
legacy, it has more or less been suggested to allow for an upgrade path 
to RHEL. Should we set this as an objective for fedora? It could
be something like ensuring that yum update can take you to the next
fedora release and then to the corresponding RHEL, without rebooting
(except for kernel upgrades, of course), or changing radically
configuration file. So, for example, FC6 users could upgrade to 
RHEL5, and FC4 users could upgrade to FC5, then FC6,
then RHEL5. In such setting I don't think that we should ensure such
upgrade path for all the apps, only 'critical' apps, likely to be
usefull on servers, like network daemons, for example. Also we could
only do that for packages that are in RHEL+EPEL. This is currently not
supported, and not an explicit goal, although there are instructions 
for the upgrade between FC versions:

http://fedoraproject.org/wiki/YumUpgradeFaq

>From reading this document, it appears that this kind of upgrade isn't
possible due to kernel incompatibilities between FC4 and FC5. In case
we want to ensure the upgradeability I was referring to, such situation
should be avoided.

Maybe this goal is too conflicting with other fedora goal, especially
being bleeding edge. The big constraint is that incompatible changes
which requires rebooting or changing configurations must all happen 
between the fedora release preceding the RHEL release and the next
fedora release (in our case, all the incompatible changes should be done
between FC6 and FC7).

In any case I don't think we should support in any sense this kind of
things, but maybe we could have this as a goal, such that maintainers 
have this issue in mind when they make their decisions. We could also
do some tests like EVR tests similar with what is currently done for
Fedora, but between the fedora version used as a base for RHEL and 
RHEL (in our case between FC3 and RHEL4 and FC6 and RHEL5) to ensure 
upgradability. And lastly we would then have to coordinate between the 
maintainers working on the different distros, ie between fedora and 
RHEL/EPEL maintainers (I guess they are more or less the same people, 
but maybe there may be special cases).

Another thing is that I don't think this should be a short term goal.
In my opinion there is already enough to be done with the merge, EPEL 
beginning and I guess people working on RHEL5 are busy, but maybe it
could be doable to begin to experiment with such idea (if it is not
immediatly rejected ;-) between RHEL5 and RHEL6 and try to make it happen
for RHEL7?

--
Pat