Starting from ClearCase v 8.0.0.7, it provides a limited support for CentOS 5.8 for x86 (32 and 64-bit) and CentOS 6.3 for x86 (32 and 64-bit).
To learn more: http://www-01.ibm.com/support/docview.wss?uid=swg21642397&myns=swgrat&mynp=OCSSSH27&mync=E