[Centos] Using yum to do downgrades

[seth vidal]

> Basically I am attempting a Red Hat 7.2 -> CentOS-2 upgrade.  So far it 
> has worked like a charm.  The problem is though that yum (no doubt by 
> design) will not downgrade packages to the CentOS versions.

yep. True.


> The problem is that some old RPMs have 72 in the release (for Red Hat 
> 7.2) and the newer package as 21 in the release (For Enterprise Linux 
> 2.1).  Some others are updates to 7.2 which increased the version number 
> where as 2.1 got a backported fix and increased release number.

which is what happens when something branches earlier.


> Is there a way to make yum always select a particular Vendor or 
> Distribution?  What about using yum to do an explicit downgrade
> "yum install mypackage-version-oldrelease"?
not for yum 1.0.X or 2.0.X. 2.1.x can but it's not going to work on a
rhl 7.2 or rhel2.1 one system.



> Also, this is an rpm question, does anyone know if I can do
> "rpm --erase redhat-logos" and "rpm -i centos-logos" at the same time?
rpm --erase --nodeps redhat-logos ; rpm -i centos-logos

they'll only be logo-free for a brief moment :)



> If I put an obsoletes: tag into centos-logos will yum do that for me? 
> Is that a good idea?

yum upgrade will do obsoletes, yes.

> At the moment I have a bash script which trys to work out the downgrade 
> rpm commands but I can not check dependencies.  Any other suggestions, 
> tips or tricks would be appreciated.

it's not hard to do a version comparison on any package in the tree
versus those installs and you could do: rpm -Uvh --oldpackage stuff

-sv