How to setup OpenSSH server on Ubuntu

Posted on September 29, 2024

OpenSSH (Open Secure Shell) is a free and open-source suite of security-related network connectivity tools. It provides secure access to remote systems, ensuring encrypted data transfer and authentication.

Key Features:

  1. Secure Remote Access: OpenSSH enables secure remote login, file transfer, and port forwarding.
  2. Encryption: Uses cryptographic techniques (e.g., AES, RSA, ECDSA) to protect data.
  3. Authentication: Supports password, public key, and Kerberos authentication.
  4. Secure File Transfer: Includes SFTP (Secure File Transfer Protocol) and SCP (Secure Copy) for secure file transfers.

Components:

  1. ssh: Remote login client.
  2. sshd: Remote login server.
  3. scp: Secure file copy client.
  4. sftp: Secure file transfer client.
  5. ssh-keygen: Tool for generating public/private key pairs.

Benefits:

  1. Security: Protects against eavesdropping, tampering, and man-in-the-middle attacks.
  2. Flexibility: Supports various authentication methods and encryption algorithms.
  3. Cross-platform: Available on multiple operating systems (Linux, macOS, Windows).

Common Use Cases:

  1. Remote System Administration
  2. File Transfer
  3. Secure Tunnels (Port Forwarding)

Installation

Note:
Ubuntu Server should already have OpenSSH server pre-installed.
Ubuntu Desktop may not have OpenSSH server pre-installed.

1) Install the package

sudo apt update && sudo apt upgrade
sudo apt install openssh-server

2) Start the SSH Server

sudo systemctl enable --now ssh

3) Check the status

sudo systemctl status ssh

4) Configure the firewall

Check this article for how to protect your OpenSSH server: 
Protect your OpenSSH server on Ubuntu using UFW

5) Connect to the server

Default SSH Port is 22.

ssh <username>@<ip-address>

OR use a tool like PuTTY

Download from: https://putty.org/

6) If you want to change the port number (Optional)

Create the backup of the original settings:

sudo cp /etc/ssh/sshd_config /etc/ssh/sshd_config.original

Open the config file:

sudo nano /etc/ssh/sshd_config

Change the port number:

Port 32501
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

Restart the SSH service:

sudo systemctl restart ssh

Connect to the server:

ssh -p <port-number> <username>@<ip-address>

Useful links:

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