Introduction to upgrading

About every 9 to 12 months, a new major version of Drupal is released that introduces many new features. If you are not running the latest major version then you will need to upgrade in order to take advantage of these features. Only 2 major versions are supported at a time (currently the 5.x and 6.x series).

Between major releases there are usually several minor releases that fix security issues and also fix bugs reported by the community. Upgrading your Drupal site to the latest corresponding minor version is strongly recommended in order to close any known security vulnerabilities in the version of Drupal core that you are running.

Upgrading your Drupal site involves several steps, which are described in more detail on the other pages of this section of the handbook:

1. Backup your existing site and database.
2. Place the site in "off-line" mode (admin >> settings >> site maintenance).
3. Download and unzip the new Drupal files, and carefully review the information and instructions available in the file UPGRADE.txt (located in the root of your installation directory).
4. Switch your site's theme to a default theme (Garland or Bluemarine), and disable all contributed or customized modules.
5. Upload the new Drupal files to your server.

   Be aware that if you browse to your site at this point in the process you will see the standard installation script. Since you are only upgrading you should NOT run this script. If you run the installation script it will likely produce errors.

   NOTE: If you are upgrading to a new major version (e.g. 5.x to 6.x), it is recommended that you remove the old version's code and modules completely before uploading the new version's code.

6. Run the update.php script, which will update your database.
7. Re-enable your contributed modules and run update.php
8. Re-enable your theme and if necessary run update.php

However, to make your update run as smoothly as possible, there are various preparations that experienced Drupal users do to guarantee the least frustrating upgrade and minimal interruption to their users. These best practices are represented in this full tutorial along with the basic steps.

NOTE: Before deciding to perform a major upgrade ( e.g. 5.7 to 6.x), you should check to see if the contributed modules you rely on have a compatible version for your planned Drupal upgrade. Old versions of modules will not run on an upgraded version of Drupal (e.g 5.7 modules do not work on a Drupal 6.x site). However, if you are only upgrading from one minor version of Drupal to another (e.g. 6.2 to 6.4), your modules should still continue to work.