Overview

SSH (Secure Shell) allows you to securely connect to a remote computer over the internet. It encrypts your connection, letting you execute commands safely on another machine without physical access. SSH enables remote management, secure file transfers, and automation. It encrypts communication to prevent unauthorized access.

Requirements

  • Linux distribution (server and client)
  • Sudo privileges on the server
  • Internet connection

Setting Up an SSH Server

Step 1: Installing SSH

sudo pacman -Sy openssh

Step 2: Enable, Start and Verify SSH Daemon

sudo systemctl enable sshd
sudo systemctl start sshd
sudo systemctl status sshd

Step 3: Configuring the Firewall

If you have a firewall enabled, you need to allow SSH connections through it.

sudo ufw enable  # If not already enabled, check using 'sudo ufw status'
sudo ufw allow ssh
sudo ufw reload

TCP port 22 is used by default for SSH connections.

Connecting from a Client

Step 1: Install SSH

sudo pacman -Sy openssh

Step 2: Find Server’s IP address

On the server, run the following command to find its IP address:

ip addr show

Look for the inet entry under the network interface you are using (e.g., eth0, wlan0). It will look something like this: 192.168.1.10

Step 3: Connect to Server

ssh username@server_ip

The first connection may show a warning about server authenticity. This is normal.

Changing SSH Port

Step 1: Editing the configuration

By default SSH uses the port 22 for connections. You can change it.

sudo nvim /etc/ssh/sshd_config

You need sudo permissions for this.

  1. Find the following line: #Port 22
  2. Uncomment by removing the # and changing the port to your desired port. For example, Port 4235
  3. Save and exit the file.

Step 2: Restarting the SSH Service

sudo systemctl restart sshd

Step 3: Update Firewall Rules

You need to allow the new port through the firewall. For example, if you changed it to 4235, run:

sudo ufw allow 4235/tcp
sudo ufw reload

Step 4: Check the firewall status

Check if the newly assigned port has been allowed:

sudo ufw status

Step 5: Connecting using new port

If port 4235 was assigned, connect using:

ssh -p 4235 username@server_ip

Optional: Key-Based Authentication

Key-based authentication is a more secure way to connect to your SSH server compared to password authentication. It uses a pair of cryptographic keys: a public key and a private key.

Step 1: Generating the Key

ssh-keygen

Press Enter to accept the default file location and name. You can also set a passphrase for added security, but it’s optional.

This will create two files in your ~/.ssh/ directory:

~/.ssh/id_ed25519        ← private key
~/.ssh/id_ed25519.pub    ← public key

Step 2: Copy the Public Key to the Server

ssh-copy-id username@server_ip

After entering your password, SSH login will use your key instead of a password.