Migrating a website script version is one of the most complicated procedure a webmaster has to deal with when managing a website. Migrating from Drupal 7? Here is a small guide with various details. Let’s start with general info : Where does my Drupal installation live? Well, if your first step has been to download Drupal to your computer, it won’t be able to work there. It likes to live on a server, not on your computer at home. In the future, when you’ve developed your new site a bit, you’ll want to put it on the internet, and your Drupal installation will sit on your server in a little folder. That’s where it’s happiest. In the beginning though, if you’re going to build your site on your computer at home, you’ll need to download a pretend server environment, like Dev Desktop from Acquia, http://www.acquia.com/downloads, that will let you run Drupal on your computer.
Note: Earlier, there used to be a migrate_plus module in Drupal 8 core which contained all the pieces of migrate functionality that wasn’t able to make it in the Drupal 7 core. It contained all the plugins for the support of XML, CSV and JSON data sources along with the support for databases like MS SQL or Oracle. This module has now been split into different modules, namely migrate_plus, migrate_tools and migrate_source_csv. After proceeding, you will be brought to the Migrate UI where you can check all the potential issues and errors that you might encounter as well as all the available and the missing paths. Go through this screen and when satisfied, start the migration.
Upgrading is the process of moving your site from a previous major version of Drupal to a newer version, for example from Drupal 7 to Drupal 8. This consists of upgrading the codebase to the appropriate version and then migrating the data from your old site into the new one. Drupal 8 core contains two modules to help facilitate this process: Migrate Drupal and Migrate Drupal UI.
Update your site to the latest version of Drupal 6 (core and contributed modules). Before upgrading to Drupal 7, disable and uninstall modules you know you won’t be using in the new site. To help determine which modules to uninstall, you could review the list of modules included in the distribution, which often are found in the download in the directory profiles/[distribution_name]/modules. If a given module is not in the distribution and you don’t foresee needing its functionality on your new site, you may choose to uninstall it.
The steps above outline how to get a distribution minimally installed on an existing site. But you’ll still have a lot of work to do to reconcile your existing site content and structure with what has been created by the distribution. Here are a few tips to get you started–but you should begin with the assumption that there will be lots more you’ll discover and need to fix. If the distribution is installed from scratch, we can be sure that the components we’re creating won’t conflict with existing components on the site. But when we’re converting an existing site into a one based on a distribution, there’s the potential that a component we’re creating will have the same name as one that already exists on the site. In certain cases, such a conflict can cause a site error that’s difficult to resolve. Read extra info on Drupal 8 Upgrade.