Can I fetch a unique server machine identifier with node.js?

Node has no built-in was to access this kind of low-level data.

However, you could execute ifconfig and parse its output or write a C++ extension for node that provides a function to retrieve the mac address. An even easier way is reading /sys/class/net/eth?/address:

var fs = require('fs'),
    path = require('path');
function getMACAddresses() {
    var macs = {}
    var devs = fs.readdirSync('/sys/class/net/');
    devs.forEach(function(dev) {
        var fn = path.join('/sys/class/net', dev, 'address');
        if(dev.substr(0, 3) == 'eth' && fs.existsSync(fn)) {
            macs[dev] = fs.readFileSync(fn).toString().trim();
        }
    });
    return macs;
}

console.log(getMACAddresses());

The function returns an object containing the mac addresses of all eth* devices. If you want all devices that have one, even if they are e.g. called wlan*, simply remove the dev.substr(0, 3) == 'eth' check.

If you're just looking for a unique server id, you could take the mongodb/bson approach and use the first n bytes of the md5 hash of the server's host name:

var machineHash = crypto.createHash('md5').update(os.hostname()).digest('binary');

This code is from node-buffalo. Not perfect, but may be good enough depending on what you're trying to do.

I found the solution using balupton's getmac: https://npmjs.org/package/getmac

I tried the getmac package but it would not work for me (node v0.10, Mac OS X) - so I set out and built my own: https://github.com/scravy/node-macaddress . It works in Windows, OS X, Linux, and probably every unix with ifconfig :-)