Use the harddrive /dev/sda1 and send the usage percentage to Graphdat to create a custom graph

send-disk-space-to-graphdat.js

var _exec = require('child_process').exec;
var _https = require('https');
var _os = require('os');

var _options = {
		method: 'POST',
		host: 'api.graphdat.com',
		port: 443,
		path: '/v1/measurements',
		auth: 'sigurd@graphdat.com:api.896a98bf4f',
		headers: {'Content-Type' : 'application/json'},
};

function getDiskSpace(callback)
{
	_exec("df -k /dev/sda1", function(err, stdout, stderr) {
		// ignore errors, this is just a sample

		var lines = stdout.split("\n");
		var diskInfo = lines[1].replace(/[\s\n\r]+/g,' ').split(' ');
		var percentage = diskInfo[4].replace('%', '') / 100;
		callback(null, percentage);
	});
}

function sendToGraphdat(percentage, callback)
{
	var body = {
		"source":"sigurd-db",
		"metric":"SIGURD_DISK_SPACE",
		"measure": percentage,
		"timestamp": Date.now() / 1000
	};
	var bodyString = JSON.stringify(body);
	_options.headers['Content-Length'] = Buffer.byteLength(bodyString, 'utf8');

	var cb = function(response) {
		response.on('end', function () {
			return callback(null);
		});
	};

	var req = _https.request(_options, callback);
	req.write(bodyString);
	req.end();
}

function run() {
	getDiskSpace(function(err, percentage) {
		// ignore errors, this is just a sample

		sendToGraphdat(percentage, function(err) {
			// ignore errors, this is just a sample
			setTimeout(run, 5000);
		});
	});
}
run();