What version? Also, I may be wrong but I dont think Centos is supported by ESRI but it works and I don't think that's the issue.
IF 10.1 look at this bug:
NIM086181
ArcGIS for Server 10.1 site creation fails on Linux if an HTTP proxy server environment variable is present in one of the profile files (.bash_profile or .bashrc) for the install user, or in global profile.
Actually bug may still apply for 10.2