Change session path in PHP-FPM
If you use Linux default sessions in php are stored at
/var/lib/php/sessions/
and you want change this settings, create in your server folder sessions like this
/var/www/sessions/
Set permissions
chown -R www-data:www-data /var/www/sessions
chmod 777 /var/www/sessions
Note: www-data it`s your nginx user, you can check it in file
/etc/php5/fpm/pool.d/www.conf
Now edit php.ini and set path to your new sessions folder
session.save_path = "/var/www/sessions/"
Restart php-fpm
service php5-fpm restart