files list David Cantrell and Logan Johnson as part of the "Slackware team". Later announce statements, up to release version 8.1, include Chris Lumens. Lumens, Johnson and Cantrell are also the authors of the first edition of "Slackware Linux Essentials", the official guide to Slackware Linux. The Slackware website mentions Chris Lumens and David Cantrell as being "Slackware Alumni", who "worked full-time on the Slackware project for several years." In his release notes for Slackware 10.0 and 10.1 Volkerding thanks Eric Hameleers for "his work on supporting USB, PCI, and Cardbus wireless cards". Starting with version 12.0 there is, for a second time, a team building around Volkerding. According to the release notes of 12.2, the development team consists of seven people. Future versions added people. Since version 13.0, the Slackware team seems to have core members. Eric Hameleers gives an insight into the core team with his essay on the "History of Slackware Development", written on October 3–4, 2009 (shortly after the release of version 13.0). Packages Management Slackware's package management system, collectively known as pkgtools, can administer (), install (), upgrade (), and remove () packages from local sources. It can also uncompress () and create () packages. The official tool to update Slackware over a network or the internet is . It was originally developed by Piter Punk as an unofficial way to keep Slackware up-to-date. It was officially included in the main tree in Slackware 12.2, having been included in since Slackware 9.1. When a package is upgraded, it will install the new package over the old one and then remove any files that no longer exist in the new package. When running , it only confirms that the version numbers are different, thus allowing downgrading the package if desired. Slackware packages are tarballs compressed using various methods. Starting with 13.0, most packages are compressed using xz (based on the LZMA compression algorithm), utilizing the filename extension. Prior to 13.0, packages were compressed using gzip (based on the DEFLATE compression algorithm), using the extension. Support for bzip2 and lzip compression was also added, using the filename extensions and respectively, although these are not commonly used. Packages contain all the files for that program, as well as additional metadata files used by the package manager. The package tarball contains the full directory structure of the files and is meant to be extracted in the system's root directory