Disabling IPv6 in Ubuntu/Debian and CentOS/RedHat

Disabling IPv6 in Linux distributions like Ubuntu/Debian and CentOS/RedHat can be done in a few simple steps. Here is a detailed guide on how to disable IPv6 in these distributions.

General steps for each:

For Ubuntu/Debian:

Edit sysctl.conf:
Open the /etc/sysctl.conf file in a text editor with superuser privileges. For example, use sudo nano /etc/sysctl.conf.
Add the following lines to the end of the file:

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

Save and close the file.

Apply Changes:
Run the command sudo sysctl -p to apply the changes without rebooting.

For CentOS/Red Hat:

Edit Network Configuration:
For each network interface, edit the configuration file located in /etc/sysconfig/network-scripts/. For example, for interface eth0, the file is /etc/sysconfig/network-scripts/ifcfg-eth0.
Add the line IPV6INIT=no.

Disable IPv6 Kernel Module:
Edit /etc/default/grub and add ipv6.disable=1 to the GRUB_CMDLINE_LINUX line, so it looks something like: GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet ipv6.disable=1".
Regenerate the GRUB configuration with sudo grub2-mkconfig -o /boot/grub2/grub.cfg (for BIOS systems) or sudo grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg (for UEFI systems).

Restart Network Services or Reboot:
Restart the network services using sudo systemctl restart network or reboot the system for the changes to take effect.

Important Notes:

Disabling IPv6 might not be suitable for all environments. Ensure that it’s compatible with your network requirements.
The steps might slightly vary depending on the specific version of the operating system.
Always backup configuration files before making changes.

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