Installing OpenSSH Server on Ubuntu

This tutorial should work on any distro based on Debian, but I have only tested it on Ubuntu 12.04.4.
You will need to run the commands as root or via sudo, which is the prefered method for Ubuntu.

Installing

If you decide to install OpenSSH-server, make sure you are using a strong password, at least 10 to 15 characters long, or use key-based authentication.

In order to install OpenSSH-server, you need to run this command, which will get an updated list of avalible packages and then install openssh-server.

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

Once it is installed, you can connect by typing this from another Linux or OSX machine:

ssh username@host

You can connect from a Windows machine by using one of the various SSH clients out there. I use PuTTY, myself.

Configuring

The configuration file for sshd is called sshd_config and is located in /etc/ssh/. It is commented, so you can see what the various options do. You can also look at the man page as well: man sshd

For the most part you can leave most of the settings alone, but I recommend changing two settings - LoginGraceTime and PermitRootLogin.

I changed LoginGraceTime to 20:

LoginGraceTime 20

That means it will allow someone to sit at the login prompt for only 20 seconds, instead of 2 minutes.

I also changed PermitRootLogin to without-password. You can set this option to yes, no, or without-password

PermitRootLogin no

That means that you will not be able to login as root at all. If you need root access, you can just login as your normal user and then use sudo or su to get to a root prompt.

Note: Be sure to create another user if you are going to disallow root logins and root is the only account on your server.

Whenever you make a change to the sshd configuration, make sure to restart sshd:

sudo service ssh restart

That is it, enjoy having SSH access.