Introduction
SSH (Secure Shell) is a protocol that allows secure remote login and other network services over an unsecured network. This tutorial will show you how to use SSH to connect to remote servers securely.
Prerequisites
- A remote server with SSH access.
- SSH client installed on your local machine (usually pre-installed on Linux and macOS).
Step 1: Install SSH Server on Remote Machine (if necessary)
On the remote server, ensure that OpenSSH Server is installed:
sudo apt update sudo apt install openssh-server -y
Step 2: Find the Server’s IP Address
On the remote server, find its IP address:
ip addr show
Look for the inet address under the network interface (e.g., eth0).
Step 3: Connect to the Remote Server
From your local machine, open a terminal and connect using SSH:
ssh username@server_ip
Replace username with your remote server’s user and server_ip with the IP address.
Step 4: Accept the Host Key
On the first connection, you’ll be asked to confirm the server’s fingerprint:
The authenticity of host 'server_ip' can't be established. Are you sure you want to continue connecting (yes/no)?
Type yes and press Enter.
Step 5: Enter Password
You’ll be prompted to enter the password for the user account.
Step 6: Using SSH Keys for Authentication (Recommended)
Generate an SSH key pair on your local machine:
ssh-keygen -t rsa -b 4096
Press Enter to accept the default file location and optionally set a passphrase.
Copy the public key to the remote server:
ssh-copy-id username@server_ip
Alternatively, manually copy the contents of ~/.ssh/id_rsa.pub to the remote server’s ~/.ssh/authorized_keys file.
Step 7: Disable Password Authentication (Optional)
For enhanced security, you can disable password authentication:
- Edit the SSH configuration file on the remote server:
sudo nano /etc/ssh/sshd_config
- Set the following parameters:
PasswordAuthentication no ChallengeResponseAuthentication no
- Restart SSH service:
sudo systemctl restart sshd
Step 8: Secure SSH Configuration
Additional security measures:
- Change the default SSH port (e.g., to 2222):
Port 2222
Remember to update firewall rules accordingly.
- Allow specific users:
AllowUsers your_username
Conclusion
You have learned how to use SSH for secure remote access, including setting up key-based authentication and securing the SSH server configuration.
