Debian

Debian is a Linux release, that's preffered for desktop machines, but it's been becoming more popular as a server OS over the last few years as well. It is really dependable and risk-free, as fixes are released within a couple of days after an issue is discovered. Debian has a vast support community, so if you have any kind of questions or troubles with the OS or with some of the 30,000+ packages it features, you will be able to contact the developers immediately via electronic mail using special mailing lists and receive a reply in just 15-20 minutes. The Debian community gives you the top level of support possible, as your questions will be handled by the very same people who built Debian in the first place, so they have an in-depth knowledge of how their own system works. Because the Operating System is 100% free to use and distribute, no license charges will be added to your website hosting fees and you will be able to modify the code files and any other software that you install with no restrictions, to optimize the software environment for your web sites. Furthermore, Debian performs really well on any kind of hardware, because it's light and quick and does not need much memory.