http://wiki.centos.org/FAQ/CentOS5#head-47912ebdae3b5ac10ff76053ef057c366b421dc4 This tip suggests creating a /etc/modprobe.d/disable-ipv6 file. However modprobe from module-init-tools >= 3.7 will output this warning for it: | WARNING: All config files need .conf: /etc/modprobe.d/disable-ipv6, it will | be ignored in a future release. Simply changing the recipe to create a "disable-ipv6.conf" file instead of "disable-ipv6" would make it more future proof.