If you are getting errors on a WordPress update that say you need FTP credentials, your apache install doesn’t have rights to do the changes. You could install vsftpd, but it is MUCH easier to just grant apache access to your WordPress.
sudo chown -R apache:apache path/to/wordpress
sudo chown -R apache:apache /var/www/html/
sudo chown -R www-data:www-data /var/www/html/public_html
Afterward, you should not see the error asking for FTP Credentials again. This is a very simple process and one I highly recommend due to many plugins requiring this to update.