How to Change SSH Port in Linux

Changing the default SSH port on your Linux server enhances security by reducing the risk of automated attacks targeting port 22.

Follow these steps to change the SSH port:

Backup the SSH Configuration File
Before making any changes, create a backup of the SSH configuration file:
```
sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.backup
```
Edit the SSH Configuration File
Open the SSH configuration file using a text editor like nano:
```
sudo nano /etc/ssh/sshd_config
```
Modify the Port Directive
Locate the line starting with Port 22. Uncomment the line (remove the # at the beginning) and change 22 to your desired port number (e.g., 2222):
```
Port 2222
```
Save and Exit
In `nano`, press `Ctrl + O` to save the changes, then `Enter` to confirm. Press `Ctrl + X` to exit the editor.
Update Firewall Rules
If you have a firewall enabled (e.g., UFW), allow the new SSH port:
```
sudo ufw allow 2222/tcp
```
If using firewalld:
```
sudo firewall-cmd --permanent --add-port=2222/tcp
sudo firewall-cmd --reload
```
Restart the SSH Service
Apply the changes by restarting the SSH daemon:
```
sudo systemctl restart sshd
```
Test the New SSH Port
Open a new terminal session and connect using the new port:
```
ssh username@your_server_ip -p 2222
```
Ensure you can log in successfully before closing your current session.

Important Considerations

Firewall Configuration: Ensure that your firewall allows traffic on the new SSH port to prevent being locked out.

SELinux Contexts: If SELinux is enabled, update the port contexts:

sudo semanage port -a -t ssh_port_t -p tcp 2222

While changing the SSH port can reduce automated attacks, it is not a substitute for strong authentication methods like key-based authentication.

By following these steps, you can enhance the security of your Linux server by changing the default SSH port.