openssh server ubuntu 20.04

admin3 April 2024Last Update :

Mastering OpenSSH on Ubuntu 20.04: A Comprehensive Guide

openssh server ubuntu 20.04

Welcome to the definitive guide on setting up and managing an OpenSSH server on Ubuntu 20.04. This article is crafted for system administrators, developers, and IT professionals who seek to leverage the power of secure shell (SSH) for remote administration, file transfers, and more. With a focus on security, efficiency, and best practices, we will delve into the intricacies of OpenSSH, providing you with the knowledge to deploy and maintain a robust SSH environment.

Introduction to OpenSSH and Ubuntu 20.04

OpenSSH, or Open Secure Shell, has become the gold standard for remote server management and secure communication over unsecured networks. It provides a suite of tools that facilitate encrypted data transfer, remote command execution, and other network services. Coupled with Ubuntu 20.04, a long-term support (LTS) release from Canonical, users gain a stable and secure platform ideal for hosting an OpenSSH server.

Why Choose OpenSSH on Ubuntu 20.04?

Ubuntu 20.04, codenamed Focal Fossa, offers enhanced features, improved performance, and extended security updates, making it an excellent choice for running an OpenSSH server. The integration of OpenSSH into this environment ensures a seamless experience for users requiring remote access capabilities.

Prerequisites for Installing OpenSSH Server

  • A machine running Ubuntu 20.04 LTS
  • Sudo privileges or root access
  • An active internet connection
  • Basic knowledge of Linux command line interface

Step-by-Step Installation of OpenSSH Server

Installing OpenSSH server on Ubuntu 20.04 is straightforward. Follow these steps to get your server up and running:

  1. Update your package list:
    sudo apt update
  2. Install the OpenSSH server package:
    sudo apt install openssh-server
  3. Verify the SSH service status:
    sudo systemctl status ssh
  4. If necessary, enable the SSH service to start on boot:
    sudo systemctl enable ssh

Configuring OpenSSH Server for Enhanced Security

After installation, configuring your OpenSSH server is crucial for ensuring maximum security. Here are some recommended configurations:

  • Modify the default SSH configuration file (/etc/ssh/sshd_config) to change default settings such as port number, disabling root login, and limiting user access.
  • Use public key authentication instead of passwords for added security.
  • Implement fail2ban to protect against brute-force attacks.
  • Regularly update your server to patch any vulnerabilities.

Example Configuration Changes

To change the default SSH port and disable root login, edit the sshd_config file:

sudo nano /etc/ssh/sshd_config

# Change the port number
Port 2222

# Disable root login
PermitRootLogin no

After making changes, restart the SSH service to apply them:

sudo systemctl restart ssh

Creating and Managing SSH Keys for Authentication

SSH keys provide a more secure method of logging in compared to passwords. To create an SSH key pair, use the following command:

ssh-keygen -t rsa -b 4096

Once generated, you can copy the public key to the server using:

ssh-copy-id user@server_ip

This adds the public key to the authorized_keys file on the server, allowing for passwordless authentication.

Remote Access and File Transfer with OpenSSH

With OpenSSH installed, you can remotely access your server via SSH:

ssh user@server_ip -p port_number

For secure file transfers, SCP and SFTP protocols come bundled with OpenSSH:

# Using SCP
scp -P port_number local_file user@server_ip:/remote/directory

# Using SFTP
sftp -P port_number user@server_ip

Troubleshooting Common OpenSSH Server Issues

Encountering issues with your OpenSSH server can be frustrating. Here are some common problems and their solutions:

  • Connection refused: Check if the SSH service is running and listening on the correct port.
  • Permission denied: Ensure the correct permissions are set for the .ssh directory and authorized_keys file.
  • Public key not accepted: Verify that the public key is correctly copied to the server’s authorized_keys file.

FAQ Section

How do I change the SSH port on Ubuntu 20.04?

Edit the /etc/ssh/sshd_config file and modify the Port directive, then restart the SSH service.

Can I use SSH keys and passwords simultaneously?

Yes, both methods can be enabled at the same time, but using SSH keys alone is more secure.

What should I do if my SSH service fails to start?

Check the syntax of your sshd_config file and the journal logs using journalctl -u ssh.


Setting up an OpenSSH server on Ubuntu 20.04 is a critical task for anyone looking to manage systems securely over a network. By following the guidelines provided in this article, you can establish a secure and efficient SSH environment tailored to your needs. Remember to stay vigilant with security practices and keep your server updated to safeguard against potential threats.


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