Changing the SSH port on Ubuntu 26.04

I recently got a VM from Tencent Cloud running Ubuntu 26.04. It was my first time setting up a VM on this Ubuntu release.

Whenever I set up a new VM, there are a few things I usually configure first. One of them is changing SSH from its default port, 22, to a custom port.

At first, I did it the way I was already familiar with: changing the Port setting in /etc/ssh/sshd_config, then restarting the SSH service.

sudoedit /etc/ssh/sshd_config

Then I set or uncommented the port:

Port 2234

And restarted SSH:

sudo systemctl restart ssh

But when I checked the listening ports, SSH was still using the old port.

sudo ss -tlnp | grep ssh

After digging into it, I found out that Ubuntu 26.04 uses systemd socket activation for OpenSSH, a behavior introduced in Ubuntu 22.10.

OpenSSH uses systemd socket activation, so the listening socket is managed by ssh.socket. Ubuntu also uses a systemd generator that reads the SSH configuration and generates the corresponding socket configuration.

So after changing the port, I needed to reload systemd and restart the SSH socket instead:

sudo sshd -t
sudo systemctl daemon-reload
sudo systemctl restart ssh.socket

sshd -t validates the SSH configuration before applying it, which is useful when configuring a remote server where a bad configuration could lock me out.

After restarting the socket, I could verify the new listening port again:

sudo ss -tlnp | grep ssh

The new port also needs to be allowed through both the VM’s firewall and Tencent Cloud security group. In my case:

sudo ufw allow 2234/tcp

Finally, before closing the existing SSH session, I test a new connection first:

ssh -p 2234 user@server

That way, I can make sure the new port works before disconnecting from the session that still has access to the server.

This was a small reminder that even familiar server setup tasks can behave differently across newer Linux distributions.

See Ubuntu’s explanation of OpenSSH socket activation.