CentOS - Sep 2004 - Using yum to do downgrades

This is a yum question but relates to some work I am doing with CentOS 
and other recent discussions on this list so I though I would post here 
first.

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.

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.

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"?

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?

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

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.

John.

-- 
John Newbigin - Computer Systems Officer
School of Information Technology
Swinburne University of Technology
Melbourne, Australia
http://www.it.swin.edu.au/staff/jnewbigin

> 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