How to install OpenSSH server on Ubuntu Linux?

sshd (OpenSSH Daemon) is the daemon program for SSH client. SSH replaces unreliable rlogin and rsh, and give securely encrypted communications between two untrusted hosts over the Internet. Ubuntu Desktop and minimal Ubuntu server don't come sshd installed. Nonetheless, you can undoubtedly install SSH server in Ubuntu using the following steps.

1. Install OpenSSH server

To install openssh-server package, run:

$ sudo apt install openssh-server

2. Verify that ssh service running

Run the following systemctl command:

$ sudo systemctl status ssh

If not running then run following systemctl command:

$ sudo systemctl enable ssh
$ sudo systemctl start ssh

3. Test it

Now you can login from your desktop computer (Linux, macOS, Windows using putty client) using the ssh command:

$ ssh user@server-ip

You can copy and install the public key using ssh-copy-id command for password less login:

$ ssh-copy-id user@server-ip

Ssh config file

Using ssh config, you can create shortcuts for ssh login. For example, create a file named ~/.ssh/config as follows:

$ vi ~/.ssh/config

Add the following snippet to create login shortcut for your server: 

Host web01
        HostName server-id
        Port 22
        IdentityFile  ~/.ssh/private_key
        User server-username

To login run following command on terminal:

ssh web01