Before you continue reading, we need to define the difference between upgrading and updating:
- Upgrading refers to moving from one major release to another, e.g. you are moving from Drupal 7 to Drupal 8.
- Updating typically refers to bringing your site up to the latest minor version of Drupal, e.g. such as updating from Drupal 7.12 to Drupal 7.14.
For information on updating your Drupal site see: http://www.drupal.org/node/1223018
Upgrading your Drupal installation
The process of upgrading to the latest version of Drupal can vary in difficulty depending on the complexity of your current installation. This guide aims to help you plan for and complete a successful upgrade regardless of the size or complexity of your current site.
Any Drupal upgrade has four general steps: Planning, Preparing your current site for upgrade, Upgrading, and Testing.
Before you begin reading this guide, please make note of the following.
Upgrading Between Versions
You can upgrade from Drupal 6 to Drupal 7.
To move to Drupal 8, use the new migration process. It allows you to migrate from Drupal 6 or Drupal 7 to Drupal 8. See Upgrading from Drupal 6 or 7 to Drupal 8.
Backing Up Your Existing Site
Regularly backing up your site is considered a best practice. A full backup of your site database, core Drupal files, non-core files (e.g. contributed modules, and file upload folders), and directory/file permissions (if running on Linux) is strongly recommended before starting any site upgrade.
You may also wish to familiarize yourself with restoring your site from a backup prior to starting your upgrade. If something should go wrong during your upgrade and you need to restore your site from backup, it is best to be prepared so you can restore your site quickly. See [link] for more information on how to back up and restore your site.
You should also review Copying a live site via command line.
- Drupal core issue queue (http://drupal.org/project/issues/search/drupal), set component="database update system" and select a version. Current 8.x active issues: http://drupal.org/project/issues/search/drupal?&status%5B%5D=1&version%5.... See also http://drupal.org/project/examples
- Contributed modules offer information either on the description page or in the issue queue. Set the 'Version' filter to '8.x' to find related issues (eg. 'Views') and particularly for modules lacking stable D7 versions, search 'Upgrade D7' to maybe find some info and pointers beyond the dead end.
- Drupal theme upgrade : http://drupal.org/update/themes/6/7