* /var/www/wallabag/bin/
* /var/www/wallabag/app/config/
* /var/www/wallabag/vendor/
-* /var/www/wallabag/data/db/
+* /var/www/wallabag/data/
by entering
chown -R www-data:www-data /var/www/wallabag/bin
chown -R www-data:www-data /var/www/wallabag/app/config
chown -R www-data:www-data /var/www/wallabag/vendor
- chown -R www-data:www-data /var/www/wallabag/data/db
+ chown -R www-data:www-data /var/www/wallabag/data/
otherwise, sooner or later you will meet this error messages