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As a final topic, this book will discuss some ways that the case study system provides enhanced connectivity and accessibility. You may not need any of this information, so feel free to skim it. However, even if you don't use it, you may wish to read through this section anyway, since it provides some interesting ideas that may lead you to some of your own.
The case study system is connected to the Internet at all times via a cable modem connection. This provides the ability to access the system remotely using SSH. This isn't a commonly used feature, but every now and then it comes in very handy, so it's something to consider if you have a similar high-speed, "always on" connection. (This would be quite painful to use over a dial-up connection.)
As it happens, the configuration of OpenSSH for the desktop system is nothing more than the installation discussed in Chapter 8. Everything in that chapter applies to this case study; however, the case study installation is based on the standard RPM packages of OpenSSH provided by Red Hat, so the system wasn't built from source code. Otherwise, you can read Chapter 8 for more information.
The ability to provide secure, encrypted access to the system can be very convenient. For example, if you're traveling, you can log in to the system to check your email (either using a command-line program, or by using SSH's ability to forward X Window connections automatically if you use a graphical client). Perhaps more importantly, running OpenSSH allows the files on the system to be accessed remotely, with the scp (secure copy) and sftp (secure FTP) utilities. This can be extremely useful if you forgot a file at home that you need at work, or while on the road. Just remember to keep the system up to date, to avoid exposing yourself to needless security vulnerabilities.
Another, perhaps more novel feature provided by the desktop is a personal web proxy server. Many businesses use a firewall to protect the corporate network, which in turn requires users to use a proxy server. Frequently these proxy servers perform various filtering techniques to restrict user access to some material on the web. This is sometimes done to protect the company's good name. For example, it might cast the company in a bad light if its employees are observed visiting questionable sites while on the job! Of course, sometimes the corporate proxy server is just too slow, or even down.
Before using any of the techniques in this section, check with your network administrators to make sure it's permitted! Not all employers may permit these types of connections.
It's possible to run a proxy server such as tinyproxy (available at http://www.tinyproxy.sourceforge.net) on your home desktop system connected directly to the Internet, as with the case study system. By then logging into your home system from your desktop system using OpenSSH and setting up SSH port forwarding, you can access your proxy server at home from your computer at work. (Generally you simply set your web browser to use "localhost" as the proxy server, and set up SSH port forwarding to redirect those requests across the SSH link to be serviced by your personal proxy server running outside the firewall.)
This means that all your web requests will appear to originate from your own personal desktop computer, outside the company's firewall. Since you run that proxy server, you are not restricted in the sites you can visit. This can be a great feature for you at work, if the corporate proxy is blocking access to sites you need, or is malfunctioning or bogged down.
However, you shouldn't just go off and set this up! Many companies would not approve of this behavior, and you might be violating a company policy if you do this. This configuration is easy to set up, but before you do it's important to check with your network administrators for approval. Your employer may prefer or require that you not do this. This technique is presented here simply to demonstrate some of the creative things you can do with a Linux system, once you've mastered it. Don't blame us if you use this technique (or one like it) and something unfortunate happens!
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