Update: For the latest instructions on how to upgrade DotNetNuke read this tutorial.
This is a new post, based on information I originally posted on my blog at DotNetNuke.com a few years ago.
Upgrading DotNetNuke is actually fairly easy, you can do so with ease in most cases, though occasionally you may run into a problem or two. If you follow the steps below you should be able to recover from any issues and get your website back up and running in its original state.
If you're upgrading your DotNetNuke instance, here is a list of simple steps to follow during the upgrade process.
First tip, test the upgrade on a staging site first, pull a copy of the database and files down, try the upgrade, make sure all your functionality is still there. Then upgrade production (backup everything first!!!!!)
Here’s the steps to upgrade
1. Backup the database.
2. Backup the file system.
3. Make sure you did 1 & 2.
4. Extract the latest DNN ZIP file somewhere, you should download this zip file from DotNetNuke.com, and start with the UPGRADE package. (this assumes you are upgrading from DNN 4.6.2 or greater, if not you should use the Install package but there are additional steps required.)
5. Copy the contents of the extracted UPGRADE package over the existing site files.
6. Load the website, this will cause the upgrade to begin when the page loads. Make sure the upgrade process completes successfully.
7. At this point you should be done with the upgrade itself, and now it is time to do some testing to make sure that the upgrade worked and doesn’t cause any problems on your website.
Like I said, test first, just to be sure you have everything working properly.
Another thing you might check out is this blog post from Will Strohl that has a recommended upgrade path. While you should be able to go from 4.6.2 straight to the current release, sometimes it is better to do it in steps as Will's post lays out.
For some more advanced upgrade scenarios, such as disabling your site before upgrade, check out the Wiki entry on DotNetNukeDocs.com for upgrades.