Remote access is themain method while managing Linux systems. Remote access must be secured accordingly. Openssh suite which implements Ssh provides this security with server and client side. Openssh also provides auxiliary tools to make copying or identity management easily and securely.
Openssh servers run by default tcp port 22. We call it generally ssh port. Ssh port number is know for the whole world so attackers can attack to beat our Openssh server like brute forcing.
Get Ssh Server Port Number From Ssh Configuration
Ssh server configuration file can be found at /etc/ssh/sshd_config . We will find related configuration line like below.
$ grep Port /etc/ssh/sshd_config
$grep Listen /etc/ssh/sshd_config
We can see that default configuration is used for ports because they are commented.
Change Ssh Server Port Number
We will open configuration file and add line below
Keep in mind be sure there is no other application using this port.
Restart Ssh Server To Apply Configuration
Just changing configuration file is not enough to take port change. We will restart our Openssh server like below to load with new configuration.
$ sudo systemctl restart sshd
Check New Port
We can check the new port number of Openssh server like below.
$netstat -tln | grep 2134
tcp 0.0.0.0:2134 0.0.0.0:* LISTEN
tcp6 :::2134 :::* LISTEN
Connect Ssh With Different Port Number
By default while using
ssh command we do not provide the port number 22 explicitly.
ssh command assumes the port number 22. But what if we need to connect ssh server which port is different than 22. We will specify port number with
-p option. In this example we will connect port number 2134
$ ssh -p 2134 poftut.com