"Source database does not contain a recognizable Drupal version." I have installed two Drupal sites in my local Ubuntu desktop 15.10 Apache2 (2.4.12) environment: One is a fresh install of Drupal 8 and The second is a copy of an existing working site built with Drupal 7 (which is mostly core-modules based, very humble by means of pages). Both sites are working fine without any problem, anywhere.

My aim is first and foremost upgrading the Drupal 7 site to Drupal 8. I did all the preliminary stages like configuring the same languages, Keep minimal by means of modules (uninstalling any modules in the D7 site that I could easily bring back after the Upgrade), making sure the same modules are installed in both sites, etc, and now I just want to "Transcend" (hope its a good phrasing) my Drupal 7 site into the fresh Drupal 8 one.

To achieve my aim I've installed the Drupal Upgrade module in my Drupal 8 site, went to localhost/sitename/upgrade, and filled in all the details of the Drupal 7 site. 

When I clicked the "Review upgrade" button I got the error:


  Source database does not contain a recognizable Drupal version.


I've googled this error as an exact phrase ("Error") and found very few results; Most of them seem to me to require a PHP programming knowledge that I've yet acquired, so I can't determine if the error is due to a bug (especially since this module is still under heavy development) or due to my mistake in understanding the concept\functionality of this module.


What reasons are there that the D8 Drupal upgrade module wont "like" the D7 database I provided? Especially while the Drupal 7 site is working fine both online and locally.
Would migrating be a decent alternative for upgrading, if upgrading isn't possible for whatever reason? If so, what is the best most simple solution You could think of for migration?




I went to /var/www/html/benia/modules/migrate_upgrade/src/MigrationCreationTrait.php and did:

-- return $version_string ? substr($version_string, 0, 1) : FALSE;

++ return 7;
++ return $version_string ? substr($version_string, 0, 1) : FALSE;


Than got this error in top of the screen.
At this stage, I don't think there is a simple option to upgrade from 7 to 8. As you can see on the release note: 


  Once you are ready, Drupal 8 core also includes the Migrate module to
  update existing Drupal 7 and 6 sites to Drupal 8 directly. Migrate is
  marked "experimental" in Drupal 8.0.0, but will be fully supported in
  an upcoming release.
  https://www.drupal.org/news/drupal-8.0.0-released


A little bit technical behind the scene: 
From 7 to 8 version, they keep the same concept when building site (like node, entity, permission, views...) but not the core. I would say: they changed everything to OOP, Symfony component, architecture... 
So there is no way to upgrade your drupal site directly from decent version to 8.0, you have to migrate. Here is how the migrating process should look: 


Recreate the site with the same functionality to your d7 site. 
Recreate the theme (using twig template)
Migrate content over 


The cost to this process is (unfortunately) same to recreate a new site or more. 
With the no 3, take a look at this article by Phase 2: https://www.phase2technology.com/blog/upgrading-to-a-drupal-8-site/