I have a VPS and use it for hosting my sites. The server is nginx with php-fdm.
my site is in the
The user you are logging in as is not the www-data user or a member of the www-data group.
I set things up on my servers so that the user I log in as owns the files/directories, and a webuser group is the owning group, perms are set to 750/640. You can automagically keep the owning group the same across all files/directories uploaded to/created on the server by making the top level web directory setgid.
drwxr-s--- 4 debbie www-data 4096 Oct 6 2015 /var/www-debbie.example.com
If the webserver needs to write files, create the directory and change the permissions on it
sudo mkdir /var/www-debbie.example.com/writeable sudo chmod 770 /var/www-debbie.example.com/writeable
If you haven't done the setgid thing, then fix the ownership
sudo chown debbie.www-data /var/www-debbie.example.com/writeable
And there ya go, the web server user can write to it.
drwxrws--- 4 debbie www-data 4096 Oct 6 2015 /var/www-debbie.example.com/writeable