Ubuntu is a popular desktop OS, which uses the Linux kernel, but its server release is getting really popular too. The reason is that the operating system is really light and it'll function on almost any hardware without any issues, utilizing its resources to the maximum. Ubuntu is also extremely reliable and secure and all Long-Term Support (LTS) releases are supported for a minimum of 5 years, which warrants that you will have a protected and dependable software environment on your server all of the time. Also, Ubuntu has one of the largest user communities in the world, which means that if you experience any issue or have any kind of question, you'll find lots of resources on the net. One of the main advantages of this OS is the fact that it contains thousands of software packages which can be freely changed in accordance with your needs and / or the needs of the applications that you need to run, not to mention that you won't have to pay any kind of license fees at any time. In contrast, other OS's are paid and their code is not accessible, which means that it can't be changed.