+Comprehensive documentation on upgrading to the latest version of the software
+is available at http://www.mediawiki.org/wiki/Manual:Upgrading.
+
+=== Consult the release notes ===
+
+Before doing anything, stop and consult the release notes supplied with the new
+version of the software. These detail bug fixes, new features and functionality,
+and any particular points that may need to be noted during the upgrade
+procedure.
+
+=== Backup first ===
+
+It is imperative that, prior to attempting an upgrade of the database schema,
+you take a complete backup of your wiki database and files and verify it. While
+the upgrade scripts are somewhat robust, there is no guarantee that things will
+not fail, leaving the database in an inconsistent state.
+
+http://www.mediawiki.org/wiki/Manual:Backing_up_a_wiki provides an overview of
+the backup process. You should also refer to the documentation for your
+database management system for information on backing up a database, and to
+your operating system documentation for information on making copies of files.
+
+=== Perform the file upgrade ===
+
+Download the files for the new version of the software. These are available
+as a compressed "tar" archive from the Wikimedia Download Service
+(http://download.wikimedia.org/mediawiki).
+
+You can also obtain the new files directly from our Subversion source code
+repository, via a checkout or export operation.
+
+Replace the existing MediaWiki files with the new. You should preserve the
+LocalSettings.php file and the "extensions" and "images" directories.
+
+Depending upon your configuration, you may also need to preserve additional
+directories, including a custom upload directory ($wgUploadDirectory),
+deleted file archives, and any custom skins.
+
+=== Perform the database upgrade ===
+
+==== From the web ====
+
+If you browse to the web-based installation script (usually at
+/mw-config/index.php) from your wiki installation you can follow the script and
+upgrade your database in place.
+
+==== From the command line ====
+
+From the command line, browse to the "maintenance" directory and run the
+update.php script to check and update the schema. This will insert missing
+tables, update existing tables, and move data around as needed. In most cases,
+this is successful and nothing further needs to be done.
+
+=== Check configuration settings ===
+
+The names of configuration variables, and their default values and purposes,
+can change between release branches, e.g. $wgDisableUploads in 1.4 is replaced
+with $wgEnableUploads in later versions. When upgrading, consult the release
+notes to check for configuration changes which would alter the expected
+behaviour of MediaWiki.
+
+=== Check installed extensions ===
+
+Extensions usually need to be upgraded at the same time as the MediaWiki core.
+
+In MediaWiki 1.14 some extensions are migrated into the core. Please see the
+HISTORY section "Migrated extensions" and disable these extensions in your
+LocalSettings.php
+
+=== Test ===
+
+It makes sense to test your wiki immediately following any kind of maintenance
+procedure, and especially after upgrading; check that page views and edits work
+normally and that special pages continue to function, etc. and correct errors
+and quirks which reveal themselves.
+
+You should also test any extensions, and upgrade these if necessary.
+
+== Upgrading from 1.16 or earlier ==
+
+If you have a Chinese or Japanese wiki ($wgLanguageCode is set to one
+of "zh", "ja", or "yue") and you are using MySQL fulltext search, you
+will probably want to update the search index.
+
+In the "maintenance" directory, run the updateDoubleWidthSearch.php
+script. This will update the searchindex table for those pages that
+contain double-byte latin characters.
+
+== Upgrading from 1.8 or earlier ==
+
+MediaWiki 1.9 and later no longer keep default localized message text
+in the database; 'MediaWiki:'-namespace pages that do not exist in the
+database are simply transparently filled-in on demand.
+
+The upgrade process will delete any 'MediaWiki:' pages which are left
+in the default state (last edited by 'MediaWiki default'). This may
+take a few moments, similar to the old initial setup.
+
+Note that the large number of deletions may cause older edits to expire
+from the list on Special:Recentchanges, although the deletions themselves
+will be hidden by default. (Click "show bot edits" to list them.)
+
+See RELEASE-NOTES for more details about new and changed options.
+
+== Upgrading from 1.7 or earlier ==
+
+$wgDefaultUserOptions now contains all the defaults, not only overrides.
+If you're setting this as a complete array(), you may need to change it
+to set only specific items as recommended in DefaultSettings.php.
+
+== Upgrading from 1.6 or earlier ==
+
+$wgLocalTZoffset was in hours, it is now using minutes.
+
+== Upgrading from 1.5 or earlier ==