In this tip we will see how to easily change the default SSH server port number and making it running on multiple ports under Ubuntu 11.10/12.04 or older. The default SSH port number is 22, changing it to a new port will help you avoid hackers' attack on this port. Installing an SSH server under Ubuntu can be done with the following command:

sudo apt-get install openssh-server openssh-client

To change now the SSH server port number, follow these instructions:

- Via the command line, edit this file:

sudo gedit /etc/ssh/sshd_config

- Search for Port 22 and make sure it is uncommented, then set your own port number:

- To run your SSH server on multiple port numbers, add each port in a new line as follows:

Port 22
Port 33
Port 847

- Press now CTRL+Q and save your file, then restart your SSH server with this command so that your changes take effect:

sudo /etc/init.d/ssh restart


sudo service ssh restart

- You can now test your ports by running this command:

ssh -p PORT_NUMBER localhost

Here is an example:

ssh -p 22 localhost

If you are required to submit a password, then your SSH server is listening to this selected port.

Note: this tip is also workable for Ubuntu 11.04/10.10/10.04.

That's it!

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