In the installation documentation, the passage

Clear the ini caches for the next settings to be updated:

php bin/php/ezcache.php --clear-tag=ini

Next, you will need to update the class autoloads by running the script from you ezpublish_legacy/ directory under your eZ Publish site location:

cd ezpublish_legacy/
php bin/php/ezpgenerateautoloads.php

would be more accurate if we pulled the cd ezpublish_legacy/ upwards, before the ezcache.php script invocation (since we need to be ezpublish_legacy for the path and script to work)