Edit

Open /etc/sysctl.conf and add following lines.

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

run

sudo sysctl -p

Check

cat /proc/sys/net/ipv6/conf/all/disable_ipv6

• 1 - disabled
• 0 - enabled