How to Change SSH Port in Linux for Better Security

SSH Port is the network port used by Secure Shell to connect securely to remote servers, usually port 22. You can change the SSH port by editing the sshd_config file and updating firewall rules, which helps improve server security.

To change the default SSH port in Linux Ubuntu, Debian, and CentOS, the below steps are required mainly:

• Executing sudo nano /etc/ssh/sshd_config command to open SSH configuration file.
• Find the #Port 22 to uncomment it and change the number to your considered port number.
• Apply the changes you have made by restarting the SSH service. Use ssh -p New Port Number user@host to do this.

🤖AI Overview:

SSH Port is the network port used by the SSH service to allow secure remote connections, typically port 22 by default. Changing the default SSH port can improve security by reducing the risk of automated attacks on port 22. On Linux systems, this is done by editing the SSH configuration file and specifying a new port number, followed by updating firewall settings to allow traffic on the new port.

Notes You Should know before Changing Linux SSH Port

• It is better to specify a 4 or 5 digit port. Also, remember to use a free SSH port.
• If a firewall is used in the data center network, make sure to inform the data center of the desired port to open it.
• Be sure to write down the port you want to allocate to SSH.
• Be careful to change the SSH port as any mistake may cause you to have trouble accessing the server.
• If you do not use SELinux, you should disable it to prevent any issues with the function of your server.

Prerequisites to Change SSH Port on Linux

To let this tutorial work correctly, provide the options below and move on.

• A Server running Linux VPS.
• A non-root user with sudo privileges.
• SSH client/Terminal Window.

How to Change SSH Port in Linux Ubuntu, Debian, and CentOS

Regardless of using Ubuntu, Debian, or CentOS, you can use the below steps and change the SSH Port in Linux.

Step 1: Open the /etc/ssh/sshd_config File

Use nano or your favorite text editor to open the /etc/ssh/sshd_config configuration file:

$ sudo nano /etc/ssh/sshd_config

Step 2: Find the line containing “Port 22”

Find the line marked #Port 22. This line must be uncommented and the number must be changed to the port number you prefer.

For example, to change the port number to 14252, act like this:

From:
#Port 22

To:
Port 14252

Step 3: Save and Exit

Save the changes you have made and exit by running the command below:

$ sudo systemctl restart sshd

Run the command below to access the SSH server, specifying the port number you prefer:

ssh user@ip_address_of_server -p 14252

On Debian, type:

service ssh restart

Once the server is ready, you can easily connect to the server through Putty and the new port number should be used instead of port 22.

This time you are more secure than the last connection.

Step 4: Test Your New Port

You can attempt SSH on the new port to confirm everything is operational.

Use the following command to tell the client to use a different port than the default 22:

$ ssh -p 14252 user@localhost

Optional: To verify SSH is listening on the new port, run:

ss -tnlp | grep ssh

If everything is working well, you are ready to start a new SSH session on your new chosen port.

Step 5: Allow traffic to the new port [On Ubuntu]

Ubuntu is pre-installed with the UFW firewall.

Use the following command to allow traffic to the new port if you are using UFW firewall.

$ sudo ufw allow 14252/tcp

Step 6: Add the new Port to your Firewall [On CentOS]

Although UFW is not used by CentOS by default, if you do have it installed, be sure to run the following UFW command.

By default, CentOS employs firewalld and SELinux.

It will be necessary to create an exception to permit SSH access on the recently set port:

Run the command below to check whether SELinux is enabled or not:

# sestatus

To add a new port number for SSH, you can use the semanage tool:

# semanage port -a -t ssh_port_t -p tcp 14252

Then, in firewalld’s configured zone (“public” by default), add the new port:

# firewall-cmd --zone=public --add-port=14252/tcp --permanent

Finally, run the command below to complete the changes:

# firewall-cmd --reload

Additional Notes:

• Since Ubuntu is based on Debian, other Debian-based systems, such as Linux Mint, can also use the same procedures.
• Fedora and other Linux distributions can use its instructions because CentOS is based on Red Hat.

Conclusion

You can easily change the SSH port through the “sshd_config” file.

The SSH Port is fundamental for secure remote server management. While the default port is 22, changing it to a custom number helps enhance security by reducing exposure to automated attacks.

Proper configuration involves editing the sshd_config file, adjusting firewall rules, and testing new settings carefully.

Combining SSH port changes with strong authentication and firewall management creates a more secure environment.

For beginners, understanding and managing the SSH Port is a valuable skill to protect your Linux servers effectively.

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