yum centos3-Base http://mirror.centos.org/centos/3/os/$ARCH/
yum centos3-Updates http://mirror.centos.org/centos/3/updates/$ARCH/
yum centos3-extras http://mirror.centos.org/centos/3/extras/$ARCH/
yum centos3-addons http://mirror.centos.org/centos/3/addons/$ARCH/