Proof is an addon to the Root toolkit. xrootd was formerly part of Root, but was broken off into a separate package. Some bits of the architecture changed between the xrootd version that is in EPEL and the xrootd version that is in the Atlas repo, so the versions are not compatible.
Some of the issues I ran into:
- XrdNetDNS was renamed to XrdSysDNS in xrootd, so the code had to be patched
- XrdSut library had to be removed
- Xrd library had to be removed