Got a wild hair this A.M. and decided to inundate my two brain cells. "Man yum" includes this:
update If run without any packages, update will update every currently installed package. ... assumed to be a shell glob and any matches are then installed.
If the --obsoletes flag is present yum will include package obsoletes in its calculations - this makes it better for distro- version changes, for example: upgrading from somelinux 8.0 to somelinux 9.
Hmmm. Cell number 2 doesn't forget much. I recall several admonitions that major upgrade should take the form of a new install. E.g. CentOS 3* to CentOS 4*. The paragraph above *seems* to indicate that a major upgrade might be doable? Moreover, it prompts the questions:
1) "What are the downsides, if any?" 2) "Has anybody tried it recently?" 3) "Have any results to report?"
No pressing need, just curious.
TIA