There are 2 issues with upgrading you might encounter and get an error message like:
“downloading update Unpacking the update… Could not create directory. Installation Failed”
The first thing to do is edit your wp-config.php and use direct transfer instead of FTP. So put this line in there:
And then go to the root of your wordpress installation and type
sudo chown -R www-data .
to give the web user ownership of all files.