How to turn off ubuntu's IPv6

Modify the /etc/sysctl.conf file and add the following

net.ipv6.conf.all.disable_ipv6=1
net.ipv6.conf.default.disable_ipv6=1
net.ipv6.conf.lo.disable_ipv6=1
Execute sysctl -p to make the settings take effect

Lazy version

echo "net.ipv6.conf.all.disable_ipv6=1 \n
net.ipv6.conf.default.disable_ipv6=1 \n
net.ipv6.conf.lo.disable_ipv6=1 \n ">> /etc/sysctl.conf