[Wordpress] Unable to create directory wp-content/uploads/2016/08. Is its parent directory writable by the server

Looking for web server ownership process

Try running ps aux | grep php to see which user owns the PHP process. 

$ ps aux | grep php
root      1249  0.0  0.1 290648  5956 ?        Ss   Sep17   0:01 php-fpm: master process (/etc/php/php-fpm.conf)              
http      1278  0.0  1.0 374340 39492 ?        S    Sep17   0:21 php-fpm: pool www                                            
http      1279  0.0  1.1 374808 41460 ?        S    Sep17   0:12 php-fpm: pool www                                            
http      3934  0.0  1.0 374852 38048 ?        S    Sep17   0:17 php-fpm: pool www

It tells that the PHP process is running under the user http.
So, a quick solution will be to issue this command and give user recursive ownership of the whole WordPress installation

$ sudo chown -hR http:http PATH_TO_YOUR_WORDPRESS_FOLDER

Replacing http with whatever user is yours.
Notes: If you are using Ubuntu. The default user and group of your PHP and Web Server software is www-data.

Add below line at the bottom of wp-config.php and you are done!

define('FS_METHOD','direct');

If you continue to have errors, try to change the permissions for the wp-content and plugins folders: 

sudo chmod 777 Your_wordpress_root_folder/wp-content
sudo chmod 777 Your_wordpress_root_folder/wp-content/plugins