How to Disable IPv6 on Ubuntu 22.04 terminal

I have the NAS. Transmission is running on it. I like setting port rules on my router to make the BT service visible from the public network.

The problem is IPv6 is not working on it. So I just disabled IPv6 on Ubuntu Linux.

First I sign in to the server through putty.

Run command ip address

The 2001:270…. is the IPv6 address of this server.

Edit /etc/sysctl.conf file.

Add the following 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

Then run the command to make it effective.

sudo sysctl -p

At the last, I check the IP address.

There is no more IPv6 ip address.

On the Transmission Web Control Panel, I test the port.

Done.