Debian Package management system is a Package management systmem develop by Debian. Package management system also called package manager which contains collections of necessary file in implementing set of command or features. It is designed to time and money of organizations through eliminating the need for manual installation and updating by remote administration and software distribution technology. Debian packages have two types: Binary packages and Source packages that can be used in manipulating and managing packages or parts of packages, administering local overrides of files in a package, helping developers in constructing package archives, and assisting users in installing of packages on FTP site. Debian binary package is formatted in .deb which conforms to file name _-_.deb. Debian has a list of configuration files called conffile that ensures preservation of the local values of file contents. You can run: dpkg --status package in detemining the exact files preserved during an upgrade.