Updating a website script version is one of the most complicated procedure a webmaster encounters when managing a website. Drupal 8 upgrade guide? Here is a small guide with various details. Let’s start with basic info : Which modules to use? There are a lot of modules, lots of them doing similar or related things. You want to try not to have too many modules, because they each slow things down a little bit, and because you’ll have to maintain them (by installing updates as they are issued). http://drupalmodules.com has reviews. To help you assess the health and life expectancy of a module, look, on the module’s project page, to see how many people are using it (at the bottom of the page). Look at the top right to see how recently people have been committing to maintaining it.
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.
The Drupal core migration system is used for both importing data from custom sources, and for migrating content and configuration from previous versions of Drupal into Drupal 8 — effectively updating your site from one major version to another. Depending on which of these two tasks you’re performing you’ll use the tools in different ways.
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. Blocks and contexts. Many distributions use the Context module to position blocks. Your existing site may use the core Block module for this purpose, may use Context or some other tool, or may use a combination of tools for block placement. With your new distribution’s blocks displaying as well as those enabled by your existing site, you may get more than you need or want. To address this issue, selectively disable blocks left over from your existing site. If they were custom blocks, you may wish to delete them.
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.
You must first understand how your current site is built, and this starts with taking an accurate inventory of the Drupal modules you are currently using. This information is pretty easy to find (Administer > Site building > Modules, or go to the Available Updates page at admin/reports/updates), and this type of preparation will come in handy a bit later in your upgrade process. Will I still need this particular module in Drupal 8? Your Drupal developers are best positioned to answer this question, and they’ll certainly need some knowledge of Drupal 8 core modules ahead of time before giving a definitive “yes” or “no.” See extra details at Drupal 8 Upgrade.