Manual:Backing up a wiki

As with all such systems, it is important to make regular backups of the data in your wiki. This page provides an overview of the backup process for a typical MediaWiki wiki; you will probably want to devise your own backup scripts or schedule to suit the size of your wiki and your individual needs.

Overview
MediaWiki stores important data in two places:


 * Database : Pages and their contents, users and their preferences, metadata, search index, etc.
 * File System : Software configuration files, custom skins, extensions, images (inc. deleted images) etc.

Database
Most of the critical data in the wiki is stored in the database, which is typically straightforward to back up. When using the MySQL backend (default), various utilities are available to assist with "dumping" the database into a file, that is, generating a script file which can be used to recreate the database and all data in it from scratch if needed.

For example, the MySQL dump tool is a command-line application which can produce a dump file given the name of the database(s) to back up. Behaviour can be altered using standard parameters which will customise the output file format, for example, setting the character encoding.

There are also other tools, such as the (commercial) MySQL hot backup utility, which can back up InnoDB tables on-the-fly, and the popular third-party open-source phpMyAdmin tool, which is a web-based application containing wide functionality for interacting with a MySQL database, including a large number of options for exporting (dumping) databases.

A sample command that you may run from a crontab may look like this: /usr/bin/nice -n 19 /usr/bin/mysqldump -u $USER -p$PASSWORD $DATABASE -c | /usr/bin/nice -n 19 /bin/gzip -9 > ~/backup/wiki-$DATABASE-$(date '+%a').sql.gz

Use valid values for $USER, $PASSWORD, $DATABASE. This will write a backup file with the weekday in the filename so you would have a rolling set of backups. If you want to save the files and extensions as well, you might want to use this one.


 * Character set

Warning for MySQL 4.1 and later: In some common configurations, mysqldump can corrupt MediaWiki's stored text. If your database's character set is set to "latin1" rather than "UTF-8", mysqldump in 4.1+ will apply a character set conversion step which can corrupt text containing non-English characters as well as punctuation like "smart quotes" and long dashes used in English text.

You can see which character set your tables are using with a statement like SHOW CREATE TABLE text. The last line will include a DEFAULT CHARSET clause.

If the last line does not include a DEFAULT CHARSET clause then there is another way if you know that nobody has changed the character set of the database server since it was installed and the wiki's database was created using the default character set of the database. The STATUS command displays the database server's default character set next to Server characterset:. Here is an example output:

 mysql> status - - - - - - - - - mysql Ver 12.22 Distrib 4.0.20a, for Win95/Win98 (i32)

Connection id:         13601 Current database: Current user:          root@localhost SSL:                   Not in use Server version:        4.0.20a-nt Protocol version:      10 Connection:            localhost via TCP/IP Client characterset:   latin1 Server characterset:   latin1 TCP port:              3306 Uptime:                27 days 4 hours 58 min 26 sec 

Use the option --default-character-set=latin1</tt> on the mysqldump</tt> command line to avoid the conversion if you find it set to "latin1".

Like this: /usr/bin/nice -n 19 /usr/bin/mysqldump -u $USER -p$PASSWORD --default-character-set=$CHARSET $DATABASE -c | /usr/bin/nice -n 19 /bin/gzip -9 > ~/backup/wiki-sql-$(date '+%a').sql.gz

File system
MediaWiki stores other components of the wiki in the file system where this is more appropriate than insertion into the database, for example, site configuration files (LocalSettings.php</tt>, AdminSettings.php</tt>), image files (including deleted images, thumbnails and rendered math and SVG images, if applicable), skin customisations, extension files, etc.

The best method to back these up is to place them into an archive file, such as a .tar</tt> file, which can then be compressed if desired. On Windows, applications such as WinZip can be used if preferred.

Purge cache
You might need to purge the cache, especially if you changed some settings in the migration process. See help.

XML dump
It is also a good idea to create an XML dump in addition to the database dump. XML dumps contain the content of the wiki (wiki pages with all their revisions), without the site-related data (it does not contain user accounts, logs, etc). XML dumps are independent of the database structure, and can be imported into future (and even past) versions of MediaWiki. They are also less likely to cause problems with character encoding, and can readily be processed by third party tools, which makes them a good fallback should your main database dump become unusable, and also as a means of redistributing content en masse.

To create an XML dump, use the command-line tool dumpBackup.php</tt>, located in the maintenance directory of your MediaWiki installation. Running the command without any arguments will display a brief description of the syntax. You need to specify whether you want a full dump of the complete history of every page, or just the current contents of each page.

If an attempt to use dumpBackup.php fails, see if creating an AdminSettings.php file solves the problem.

You can also create an XML dump for a specific set of pages online, using the Special:Export, although attempting to dump large quantities of pages through this interface will usually time out.

To import an XML dump into a wiki, use the command-line tool importDump.php</tt>. For a small set of pages, you can also use the Special:Import page via your browser (per default, this is restricted to the sysop group).

As an alternative to dumpBackup.php</tt> and importDump.php</tt>, you can use MWDumper, which is faster, but requires a Java runtime environment.