Although Microsoft still dominates the desktop PCs, Linux has a large base of users in business-related settings as a server operating system. Almost all the major web sites operate on the Linux platform, including Google, Wikipedia and Facebook just to name a few. It is therefore not surprising that there is a growing demand for professionals with skills in Linux, which can command up to 30% higher salaries than those of Microsoft, who provide support to colleagues.Red Hat Enterprise Linux (RHEL) is the most popular Linux distribution among medium and large companies, and Red Hat has developed their own training and certification to ensure that professional standards are kept very high.There are three levels of certification offered by Red Hat - RHCT (Red Hat qualified person), RHCA (Red