This file provides an overview of the MediaWiki upgrade process. For help with
specific problems, you should check:

* the docs at https://www.mediawiki.org/wiki/Special:MyLanguage/Help:Contents ;
* the mediawiki-l mailing list archive at
  https://lists.wikimedia.org/hyperkitty/list/mediawiki-l@lists.wikimedia.org/ ;
  and
* the bug tracker at https://phabricator.wikimedia.org/

… for information and workarounds to common issues.

== Overview ==

We provide comprehensive documentation on upgrading to the latest version of the
software at https://www.mediawiki.org/wiki/Special:MyLanguage/Manual:Upgrading.

Important: Upgrading from releases older than two LTS release is not supported
anymore. If you want to upgrade from an old version, please upgrade to a more
recent LTS version first, then to this version.

Currently any upgrade from any version older than 1.39 will fail.

=== 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 process.

=== 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.

https://www.mediawiki.org/wiki/Special:MyLanguage/Manual:Backing_up_a_wiki is 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
(https://releases.wikimedia.org/mediawiki/).

You can also obtain the new files directly from our Git source code repository.

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 ===

As of 1.21, it is possible to separate schema changes (i.e. adding, dropping, or
changing tables, fields, or indices) from all other database changes (e.g.
populating fields). If you need this capability, see "From the command line"
below.

==== 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 use
`run.php update` 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.

If you need to separate out the schema changes so they can be run by someone
with more privileges, then you can use the --schema option to produce a text
file with the necessary commands. You can use --schema, --noschema,
$wgAllowSchemaUpdates as well as proper database permissions to enforce this
separation.

=== 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 behavior of
MediaWiki.

=== Check installed extensions ===

Extensions usually need to be upgraded at the same time as the MediaWiki core.

=== 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, that special pages continue to function, etc., and correct any errors
and quirks which reveal themselves.

You should also test any extensions, and upgrade these if necessary.
