When you get your first dedicated server, the last thing you want to do is experiment on it, especially if your server is already live on the Internet. Instead, you can use a virtual machine to run the same operating system installed on your server. With it you can do whatever kind of testing you need without the fear of ruining anything.
VirtualBox is a free and open source virtualization program distributed by Oracle (formally by Sun Microsystems). It allows you to run “guest” operating systems at real-time speeds, and you can even run multiple different OSes on the same computer.
For guest operating systems, VirtualBox currently supports all current Windows versions, most Linux distributions, Solaris, Mac OS X Server, and BSD variations. You can install the operating system without the VirtualBox environment or download a previously created image from numerous websites (usually only for free operating systems).
Once you have the OS running, it will function just like your server, and you can even connect it to the Internet through your normal network connection. There is no limit to the amount of testing you can run, and if you completely destroy the installation, just delete it and start again, with no adverse effects.
Using virtual machines is ideal for testing web server configurations, MySQL installations, software tweaks, web applications, and upgrades. With no lasting consequences, you can experiment in ways you never could with a live server. Once you are finished, it is easy to delete a guest operating system or keep it around just in case you ever need to experiment again. VirtualBox is available for free download from virtualbox.org.