An open source wiki engine which is available under the GNU General Public License.
It's used in Wikimedia projects (Wikipedia, Wiktionary, Wikisource, Wikibooks...) and many other wikis.
This documentation covers the "new" MediaWiki package of 1.27+. Documentation for the "old" package which was unmaintained, had security issues, etc. can be found in the page history. Additionally, the old mediawiki-extensions* packages are no longer supported.
The new package is available in jessie-backports and will be included in stretch. Ubuntu Xenial and Trusty users can use a PPA by the same maintainer.
There are some more details at https://www.mediawiki.org/wiki/User:Legoktm/Packages.
* pkg-mediawiki-devel list at Debian
Specified versions will be maintained as long-term supported (LTS), with support from MediaWiki developers and the distro packagers.
Debian changes to MediaWiki
We change a few things about MediaWiki to fit in with what Debian expects. Files can be found in the following places:
/usr/share/mediawiki - MediaWiki core files
/etc/mediawiki/LocalSettings.php - expected location of ?LocalSettings.php. You can also put other configuration files in this directory.
/var/lib/mediawiki - Main directory that the webserver will read from. Most core files from /usr/share/mediawiki are symlinked into this directory, and the ?LocalSettings.php file as well.
# apt install mediawiki
If you use Apache, MediaWiki will automatically be configured to serve it at http://localhost/mediawiki/. You can then visit that in your webbrowser, and go through MediaWiki's web installer.
If you use a different webserver, you'll need to manually configure it to use PHP to serve /var/lib/mediawiki.
The web installer will prompt you to download a ?LocalSettings.php file. You should save it to /etc/mediawiki/LocalSettings.php.