The recent release of Joomla 3.9.16 includes the addition of a database index to the users table. If your Joomla website happens to have duplicate usernames, this index addition will fail and you will see an error as in the attached image. The rest of the update will typically succeed just fine.
Should you have this error, you must first find and solve the duplicate username problems. Each username in your site should be unique, so you should either rename or remove duplicates.
Joomla! is a fully-featured Content Management System that runs about 3% of the world's top one million websites. Like any software, updates are released from time to time to help keep it secure, squash some bugs; and advance the feature set. In this article, we show you what steps to take when Joomla updates are pending, before and after you apply those updates.
Disclaimer - This advice will be all you need for most sites, but do feel free to contact us if you need specialist Joomla update help.
Joomla! version 3.x contains a system plugin which by default emails every super-administrator in the system notifying them when a core Joomla! update is available. The emails are not sent by the Joomla! software project but rather by the Joomla! system installed on your web server. By default, this plugin emails Superadministrator accounts once per day until the update has been applied.
In Joomla! 3.6.1 there was a bug which caused multiple emails to be sent in a short space of time. As we keep superadministrator accounts on all our JoomlaCare Managed Service customers, we received a lot of these emails - over 300 for one customer alone!
How to disable Joomla! Update Notifications
To disable these update notifications emails, while logged into your Joomla! administrator area navigate to Extensions > Plugins and search for 'Update Notification'. Then unpublish the 'System - Joomla! Update Notification' plugin in the Plugin Manager on your site. This stops the emails. When an update becomes available, you will still see a notification in the administrator area after you login.
Should I update my Joomla site?
Yes!.. but backup first! It's a good idea to keep your Joomla! software up to date because updates often contain new features as well as important security updates and fixes. However, it's important to ensure that any of the other extensions you have installed, for example components, templates, plugins, modules and language packs are compatible with the update. If you're not sure about that you can check with each extension provider. It's also always a great idea to ensure you have a validated backup before you do any sort of updating, so you have a fall back if something goes wrong. We recommend the Akeeba backup extension for Joomla backups.
What Joomla versions are compatible?
As of writing this article, the latest major release of Joomla is version 3. If your Joomla website is version 1.0.x, 1.5.x, 1.6.x, 1.7.x or 2.5.x then you can't complete a simple upgrade, many of the extensions associated with these versions are incompatible with Joomla 3 and will also need updating. In fact, the jump to Joomla 3 is so significant we need to migrate the core content, user accounts, menu items, and everything else into a new Joomla 3 system and then install and import data from any extra extensions you have in use for example Virtuemart, Kunena forum, Image Galleries, Membership components or other extensions. In all likelihood you will also need to implement a new template, which will give your website a responsive design - allowing it to be viewed well on small screen devices.
For moving between versions of Joomla 3, an upgrade is the way to go. Be sure to have a valid backup before proceeding or talk to a Joomla Expert for a free review if you're unsure!