There is a medium-sized website based on Drupal 9 that needs to be upgraded to Drupal 10. Here is a guide on how we upgrade this website.
Drupal 10
By Gast (nicht überprüft), 16 September, 2023
Problem:
User warning: mkdir(): Permission Denied in Drupal\Component\PhpStorage\FileStorage->createDirectory() (Line 123 in web/core/lib/Drupal/Component/PhpStorage/FileStorage.php).
Solution?