Availability, price and employee familiarity often determines which operating systems are offered on dedicated servers. Variations of Linux and Unix (open source operating systems) are often included at no charge to the customer. Commercial operating systems include Microsoft Windows Server, provided through a special program called Microsoft SPLA. Red Hat Enterprise is a commercial version of Linux offered to hosting providers on a monthly fee basis. The monthly fee provides OS updates through the Red Hat Network using an application called Yum. Other operating systems are available from the open source community at no charge. These include CentOS, Fedora Core, Debian, and many other Linux distributions or BSD systems FreeBSD, NetBSD, OpenBSD.
The answer to this question largely depends on two factors. Are you new to server technology and not very interested? In this case, Windows is the easiest option to get where you want to go. Do you already have experience with Linux or would you like to familiarize yourself with this operating system? If so, Linux gives you more freedoms to configure your server, and you will be using an operating system that is less vulnerable to attacks from the Internet. Linux is also open source and therefore free.