Debian GNU or Linux is a computer operating system composed of software packages released as free and open source software especially under the GNU General Public License and other free software licenses. Debian GNU or Linux uses the Linux kernel and GNU OS tools. It is distributed with access to repositories containing thousands of software packages ready for installation and use. Debian is known for relatively strict adherence to the UNIX and free software philosophies as well as using collaborative software development and testing processes. Debian can be used as a desktop as well as server operating system. It focuses on stability and security and is used as a base for many other distributions.