If your wordpress update failed with the error
The update cannot be installed because we will be unable to copy some files. This is usually due to inconsistent file permissions.: wp-admin/includes/update-core.php
Help is on the way. Just login to your webserver. Then change directory to the root of the wordpress site. And type in the following incantation:
sudo chown -R www-data:www-data .
.. tada! And dont forget the dot at the end of that command.