How To Disable IPv6 on Ubuntu 20.04 LTS

In this tutorial, we will show you how to disable IPv6 on Ubuntu 20.04 LTS. For those of you who didn’t know, IPv6 is enabled by default in Ubuntu. But you may want to disable IPv6 for many reasons. Some programs may cause problems when IPv6 is enabled, So if you are not planning to use IPv6, simply disable it and not worry about any potential problems.

This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you the step-by-step disable IPv6 on Ubuntu 20.04 (Focal Fossa). You can follow the same instructions for Ubuntu 18.04, 16.04, and any other Debian-based distribution like Linux Mint.

Prerequisites

• A server running one of the following operating systems: Ubuntu 20.04, 18.04, and any other Debian-based distribution like Linux Mint or elementary OS.
• It’s recommended that you use a fresh OS install to prevent any potential issues.
• SSH access to the server (or just open Terminal if you’re on a desktop).
• A non-root sudo user or access to the root user. We recommend acting as a non-root sudo user, however, as you can harm your system if you’re not careful when acting as the root.

Disable IPv6 on Ubuntu 20.04 LTS  Focal Fossa

Step 1. First, make sure that all your system packages are up-to-date by running the following apt commands in the terminal.

sudo apt update
sudo apt upgrade

Step 2. Disable IPv6 on Ubuntu 20.04.

On Ubuntu 20.04 IPv6 is enabled by default but most of the time organization only uses ipv4. We can disable ipv6 through mainly two ways:

• Disable kernel module.
• via sysctl settings.

Disable ipv6 via a kernel module

Now we need to edit /etc/default/grub file using your favorite text editor and make to following changes:

nano /etc/default/grub

Add the following file:

GRUB_CMDLINE_LINUX="crashkernel=auto ... ipv6.disable=1"

Once done changing any kernel parameter we rebuild grub.cfg through update-grub2:

sudo update-grub2
sudo shutdown -r now

Disable ipv6 via sysctl

Method two, we can also disable through sysctl settings, which will apply without a reboot. Now dit the system configuration file:

nano /etc/sysctl.conf

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

To apply these settings, we need to run sysctl -p:

sysctl –p

Now run the following command. You should see 1, which means IPv6 has been successfully disabled:

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

Congratulations! You have successfully Disabled IPv6. Thanks for using this tutorial for disabling the IPv6 on your Ubuntu 20.04 LTS Focal Fossa system. For additional help or useful information, we recommend you check the official UFW Firewall website.