sysctl -w net.ipv6.conf.all.disable_ipv6=1 && sysctl -w net.ipv6.conf.default.disable_ipv6=1 && sysctl -w net.ipv6.conf.lo.disable_ipv6=1

https://cwesystems.com/?p=231

 vi /etc/sysctl.conf

net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
net.ipv6.conf.lo.disable_ipv6=1
net.ipv6.conf.eth0.disable_ipv6 = 1

 vi /etc/rc.local

Before exit 0

service procps reload

Reboot