Enable SSH – Ubuntu

Here is a step-by-step guide on how to enable SSH (Secure Shell) on Ubuntu:

Step 1: Open the Terminal

First, open the Terminal application on your Ubuntu system. You can do this by searching for “Terminal” in the Dash home, or by navigating to Applications > Accessories > Terminal.

Step 2: Install SSH

sudo apt update
sudo apt install openssh-server

Step 3: Configure SSH Server (Optional – If something must be configured)

(if nano is not installed you can install it via this command: sudo apt install nano)

• Open the configuration file:

sudo nano /etc/ssh/sshd_config

• Locate the following lines:

Port 22
PermitRootLogin no
PasswordAuthentication yes

Step 4: Create a New User

sudo adduser <username>
sudo usermod -a -G sudo <username>

Step 5: Generate SSH_Key_Pair

ssh-keygen -t rsa -b 4096 -C "<username>@<hostname>"

• Enter a passphrase for your key (optional)

Step 6: Add Public Key to authorized_keys

sudo nano ~/.ssh/authorized_keys

• Paste the public key from the id_rsa.pub file into the authorized_keys file.

Step 7: Configure Firewall

sudo ufw allow <port> 

Default port for SSH is 22.

Step 8: Restart SSH Server

sudo systemctl restart ssh

Connect via SSH:

• Use a terminal client like PuTTY or Terminal to connect to your Ubuntu machine.
• Enter the hostname or IP address, port (e.g., 2222), username, and password (if not using key authentication).

Additional Tips:

• Use a strong passphrase for your key.
• Disable password authentication for production systems.
• Configure key-based authentication for multiple users.
• Consider using an client with key management features.

Troubleshooting:

• Check if the server is running. (run command: sudo systemctl status ssh)
• Verify the port is open.
• Ensure the public key is correctly added to authorized_keys.
• Check for permission issues.