1 means ipv6 is completely disabled
0 means ipv6 is not completely disabled
[mitesh@Matrix ~]$ echo "1" > /proc/sys/net/ipv6/conf/all/disable_ipv6
NOTE!: Above command disable IPv6 untill your system reboot.
/etc/sysctl.conf
file and add following linesnet.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
[mitesh@Matrix ~]$ sudo sysctl -p