Hi there. This is a quick one. Bellow instructions how to disable ipv6 on Debian Linux.
1. Log in to your machine in console mode
2. Issue the command sudo vim /etc/sysctl.conf
3. Add the following code at the bottom:
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
4. Save, close the file.
If you want re-enable IPv6, remove the above lines from /etc/sysctl.conf and reboot the machine.