Yum

Setup A Purely 64-bit System

Uninstalling 32-bit Packages

rpm -qa --queryformat '%{NAME}.%{ARCH}\n' | egrep 'i386$|i686$'

Disabling 32-bit Packages

I've seen plenty of people asking this question & not getting a good response. This is as easy as adding a single line to your /etc/yum.conf :

exclude=*.i386 *.i686