====== Configuring Ssh on Ubuntu ======
Installing and configuring SSH on Ubuntu server (If you haven't done it during installation)

If you haven't installed SSH yet, do it now:
<code bash>
sudo apt-get install openssh-server
</code>
Now, edit your /etc/ssh/sshd_config file
Set a list of users who can login
<code bash>
AllowUsers user1 user2
</code>
or deny users
<code bash>
DenyUsers user3 user4
</code>
Display a banner to the user:
<code bash>
Banner /etc/issue.net
</code>
If you want to display the same banner as to users logging in on a local console
<code bash>
Banner /etc/issue
</code>
To edit the banner itself:
<code bash>
sudo vim /etc/issue.net
</code>
And restart the ssh server
<code bash>
sudo service ssh restart
</code>
To secure you server, disable password authentication and use SSH keys to authenticate users instead
<code bash>
PasswordAuthentication no
</code>