Welcome to the CentOS 5.5 release. CentOS is an Enterprise-class Linux Distribution derived from sources freely provided to the public by our Upstream OS Provider (UOP)1.
CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes packages to remove upstream vendor branding and artwork.) CentOS is a free operating system.
CentOS 5.5 is the fifth update to the CentOS 5 distribution series. It contains updates, new functionality, and bug fixes.