Online distro upgrade

[Jeremy Katz]

On Thu, 2004-04-29 at 14:22 +0200, Aurelien Bompard wrote:
> This is probably a stupid question, but anyway...
> If I understood correctly, an upgrade from one distro to the next (say, FC1
> to FC2) will never be as good with apt or yum as it is with anaconda.
> Anaconda knows much more about the process, which packages need to be
> removed, which packages need to be installed, and what needs to be done to
> the system (ie all the SELinux labelling stuff)

Actually, SELinux doesn't get set up on an upgrade (intentionally).  The
main upgrade logic that doesn't appear elsewhere that's in anaconda is
some trickiness to get newer packages at times.   

> Are there operations which need to be done on an unmounted filesystem ? If
> yes, they could be done by a "very-first-start" program after anaconda's
> work, or even something loaded in RAM.

There are some operations that require newer libraries and newer
kernels, etc.  eg, there are a few things now that are 2.6 specific and
count on the fact that you're running a 2.6 kernel so that you can be
correctly set up to run the 2.6 kernel post-upgrade.  Having to do those
from within 2.4 is extremely difficult.  And you need to use newer
rpmlib for some features which then depends on new glibc which depends
on ..., etc

Unfortunately, while rolling upgrades can work fine if executed on a
regular basis (ie, I run the devel tree and actually update at least
once a week and regularly daily), they don't work nearly as well when
they're more of a flag day event (eg, from FC1 -> FC2).

Jeremy