Why does the i386 version of most software get installed, along with the x86_64 version, on a CentOS 64-bit system?# yum install php-xmlLoaded plugins: fastestmirrorLoading mirror speeds from cached hostfileSetting up Install Process    Package php-xml-5.3.12-5.el5.art.x86_64 already installed and latest version    Package php-xml-5.3.12-5.el5.art.i386 already installed and latest version    Nothing to do
Why does the i386 version of software get installed on an x86_64 system?
centos;64bit;32bit
CentOS has an answer on their faq page about it, it is for compatibility with 32 bit stuff. To fix it, their answer says to add exclude = *.i?86 to your yum.conf. However if you have i386 rpms installed, updates will break so make sure you remove them before doing this.I prefer setting multilib_policy=best so in the oddball case you do need something 32 bit, it will be installed but not by default.multilib_policy -  Can be set to all or best. All means install all  possible arches for any package you want to install. Therefore yum  install foo will install foo.i386 and foo.x86_64 on x86_64, if it is  available. Best means install the best arch for this platform, only.