If you’re an experienced administrator, you’ve probably used SSH to remotely access a troublesome box or your personal computer. For those who don’t know: SSH it’s a great way to fiddle with a computer from miles away as if you were sitting at its keyboard, but it’s also just about the simplest and most secure way to configure your computer to let you access its files from anywhere. You can use SSH on nearly every operating system to transfer files to and from your computer over the internet or a LAN.

Is SSH for more than commands?

SSH is traditionally used to give you remote access to a computer’s shell (command line terminal). Earlier protocols in this vein, such as telnet and rlogin, did not encrypt their traffic or take other security precautions that are necessary with untrusted networks like the internet. Depending upon the exact server, protocol, and configuration you use, SSH may be the most secure way to access a computer over a network.

If you’re a typical user, however, you may never need to access the command line—or even graphical applications—on a remote computer. Even so, SSH will still be useful in sending your latest batch of photos home from your hotel, retrieving the latest version of a report left sitting on your desktop, or for any other situation requiring a file transfer.

If you’d like to get more in depth, you can use it to load or edit a spreadsheet on another computer or keep documents synchronized between machines. If you’ve seen an experienced user work his magic with SSH, all of this may seem rather complicated. I assure you, though, that setting up an SSH server on GNU/Linux or another Unix-like operating system—and even Microsoft Windows—is as simple as installing any other software, and accessing your server from another machine running nearly any OS is even easier.

Setting up an SSH server is as simple as installing any other software, and accessing your server from another machine is even easier

Installing the server

The SSH protocol has been around for a while and several server packages have sprung up around it. The choice is a bit simpler than KDE vs GNOME, though, because almost everyone you meet will recommend OpenSSH. It’s tried, true, secure, free software developed by the OpenBSD project but made available for nearly every operating system under the sun.

If you’re using a Unix-like system such as GNU/Linux, installation really is as simple as for any other software. If your distribution has a package management utility, OpenSSH is undoubtedly available from it. In Debian and Ubuntu, it’s listed as “openssh-server”. If you normally have to install software from source, you can get the code from the OpenSSH website.

Unfortunately, things are a bit more complicated if you use Windows. You will need to use some software called Cygwin to emulate the GNU/Linux platform on your Windows box. If you are already familiar with Cygwin, you can install OpenSSH as a native package.

Wait, though! If you don’t use Cygwin already—wouldn’t you know it—someone has gone and made the whole process just as easy. The OpenSSH for Windows project has combined OpenSSH with only the absolutely necessary components of Cygwin, rolled it all up into a ball, and released it as free software on Sourceforge. Download and double click the “binary installer” as you would any other Windows setup package.

Some minor tweaking, if desired

Below, I will explore some of the configuration options of OpenSSH. Odds are your distribution has your server setup more or less like this by default, so you may safely skip this section and refer back later on if you experience problems.

OpenSSH for Windows users must also depart from the article here, as configuration on that platform works a little differently. You can refer to the README file, accessible from Start→All Programs→OpenSSH for Windows for configuration instructions. In particular, make sure to setup user passwords using the simple instructions in the readme.

For those continuing on, OpenSSH configuration can easily be done by editing a configuration file (never as scary as it sounds). On most systems, this file will be located at /etc/ssh/sshd_config. Open this file as the root user using your favorite text editor and you will find that your distribution has supplied a long template configuration file.

OpenSSH has a broad range of configuration options that can have serious effects on the security of your system. I will trust that the default settings provided by your distribution are sensible and focus on changing the configuration to serve the specific requirements of file transfer.

You could debate whether a password is more secure than other methods of authentication, but it is undeniably convenient

Password authentication

First, you can configure the SSH server to authenticate users with a password. You could debate whether a password is more secure than other methods of authentication, but it is very convenient when trying to access your machine from an arbitrary remote location where you might not have access to anything but your memory. Make sure the following line is set in your configuration file:

PasswordAuthentication yes

Remember that any line in the configuration file beginning with # is a comment, so delete the hash mark if you want to activate the line.