I wrote a quick article after actually reading the manual (wordpress codex, who woulda thought
)
Wordpress Automatic Update with SSH KBeezie
I don't have an FTP server on my box, so was kind of a pain getting automatic updates to work til I found this tweak. Essentially this is what you'd add to the wp-config.php.
And if you're not using the key pair, you can instead define a FTP_PASS.
The link has more details on setting up a private/public key pair

Wordpress Automatic Update with SSH KBeezie
I don't have an FTP server on my box, so was kind of a pain getting automatic updates to work til I found this tweak. Essentially this is what you'd add to the wp-config.php.
Code:
define('FS_METHOD', 'direct'); // 'ssh' is also an option, but did not work for my setup
define('FTP_BASE', '/opt/local/nginx/html/domain.com/');
define('FTP_CONTENT_DIR', '/opt/local/nginx/html/domain.com/wp-content/');
define('FTP_PLUGIN_DIR ', '/opt/local/nginx/html/domain.com/wp-content/plugins/');
define('FTP_PUBKEY', '/home/username/.ssh/id_rsa.pub');
define('FTP_PRIKEY', '/home/username/.ssh/id_rsa');
define('FTP_USER', 'username');
define('FTP_HOST', 'your-domain.com:22');
And if you're not using the key pair, you can instead define a FTP_PASS.
The link has more details on setting up a private/public key pair