What is CentOS? CentOS (Community enterprise Operating System), released in May 2004, is a 100% free operating system distribution based upon the Linux kernel. It is derived entirely from the Red Hat Enterprise Linux (RHEL) distribution. CentOS exists to provide a free enterprise class computing platform and strives to maintain 100% binary compatibility with its upstream source, Red Hat.
In July 2010 CentOS overtook Debian to become the most popular Linux distribution for web servers, with almost 30% of all Linux web servers using it. But in January 2012, it lost that position to Debian once again:
CentOS is one of the most popular Linux distributions in the hosting industry. Due to CentOS’ binary compatibility with RHEL, it is highly compatible with most Linux software. Most hosting control panels use CentOS as the preferred Linux distribution.
On 7 January 2014, Red Hat and CentOS announced that they would officially join forces.