How to Change SSH Port in Linux

Why Change the SSH Port?

Changing the SSH port can:

• Reduce automated brute-force attack attempts.
• Improve basic SSH security as part of your server hardening strategy.
• Make your server less visible to malicious bots scanning for open port 22.

Steps to Change SSH Port in Linux

Step 1: Log in to the Server

Before making any changes, log in to your Linux server using your current SSH port (default is 22).
For Ubuntu, switch to the root user with:

sudo -i

Step 2: Edit the SSH Configuration File

The SSH configuration file is located at:

/etc/ssh/sshd_config

Open it with the vi editor (you can also use nano if preferred):

vi /etc/ssh/sshd_config

Inside the file:

1. Search for the line containing Port by typing:

/Port

2. Uncomment the line by removing the # at the beginning.
3. Change the port number to a value between 1024 and 65535 (e.g., 15678).
   
   Example:
   Port 15678

Step 3: Save and Exit

In vi, save changes and exit by typing:

:wq

Step 4: Restart the SSH Service

For the change to take effect, restart the SSH service.

1. Ubuntu/Debian:

service sshd restart

or

systemctl restart ssh

2. CentOS 7/8:

systemctl restart sshd

Step 5: Log in Using the New SSH Port

After changing the port, your current SSH session may disconnect. To log back in:

ssh -p 15678 username@your_server_ip

Additional SSH Security Tips

Changing the SSH port is a good start, but for stronger SSH hardening, you should also:

• Disable root login (PermitRootLogin no in sshd_config).
• Use SSH key authentication instead of passwords.
• Configure a firewall to allow only the new SSH port.