Are you sure you're running Hadoop on 32bit CentOS?
I think the reason you saw that warning is the native Hadoop library $HADOOP_HOME/lib/native/libhadoop.so.1.0.0 is that it is actually expected to be compiled on a 32 bit CentOS.
It's just a warning, and won't impact Hadoop's functionalities.
If you are running CentOS 64 bit then I would suggest you to download the source code of Hadoop and recompile libhadoop.so.1.0.0 on a 64bit system, then replace the 32bit one.
Even then if the Warning is existing, then you can follow the following solution.
Steps on how to recompile source code are included here for Ubuntu:
solve this issue by ingesting these lines into my .bashrc file.
This must resolve your issue.