When running up2date on your server you receive this error.

RPM error.  The message was:
Could not determine what version of Red Hat Linux you are running.
If you get this error, try running

                rpm —rebuilddb

This usually occurs when the ‘redhat-release’ package is missing.  This often happens when you apply a version update.  You can correct this issue by installing the ‘redhat-release’ package.  When this occurs, the ‘redhat-release’ package can usually be found in the ‘/var/spool/up2date’ directory.  You can list the ‘redhat-release’ packages with the following commands.

cd /var/spool/up2date
ls redhat-release*.rpm

You will want to install the newest ‘redhat-release’ package.

ex:
rpm -Uvh redhat-release-4ES-4.1.i386.rpm