Month: December 2017

.local domain fails

This post is meant for users who can do a dns query on a local dns record but cannot access this name. E.g. dig is giving you the IP address of the host, but you cannot ping or SSH to it (and it’s not firewall related)

Recently I’ve changed my network setup and moved away from my router as DHCP/DNS server. I installed pi-hole and I’m quite satisfied.

I have several RPI’s and other material (Yún and linkit7688) running and I want to reach them via a host name. You can add the host name in “etc/hosts” file on the RPI-hole (192.168.x.x [name] [name].[local-domain name]). You can ping or ssh from different kinds of OS, but not from Ubuntu.

This is caused mdns (multicast dns, for auto configuration of the .local domain).

Check /etc/nsswitch.conf, and you will see:

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
mdns4 is what is doing multicast dns.

If you change this to, you should be able to reach the host:
hosts: files dns

The you have two options:
1.) Remove mdns permanently with sudo apt-get remove libnss-mdns
2.) don’t use .local – use .lan or something instead

I’ve chosen for option 2, due to the fact that I want Ubuntu to work “out of the box” and in my opinion it’s better to make a server side change then updating all the clients of the network.

Easy gauge chart with C3JS

When you produce data (in the field of industrial automation or IoT) you need to be able to visualize your data. I started out with the google charts library. It is really easy to use, but then I found out that you can only use this when connected to the internet. This could cause a potential problem when my customers are experiencing problems with their internet connection and you cannot show their data.

I was always charmed by D3 but compared to google charts it has a bigger learning curve. Then I found C3. C3 makes it easy to generate D3-based charts by wrapping the code required to construct the entire chart. We don’t need to write D3 code any more :-).

Below shows a gauge chart which displays values instead of the ratio (%). The default example is working with %, this actually does the trick to convert to values: format: function(value) { return value; }

<!DOCTYPE html>
<html>
<head>
	<link href="/static/c3.css" rel="stylesheet" type="text/css">
	<script charset="utf-8" src="static/d3.v3.min.js">
	</script>
	<script src="/static/c3.min.js">
	</script>
	<title></title>
</head>
<body>
	<div id="chart"></div>
	<script>
	   var chart = c3.generate({
	   data: {
	       columns: [
	           ['data', 91.4]
	       ],
	       type: 'gauge',
	       onclick: function (d, i) { console.log("onclick", d, i); },
	       onmouseover: function (d, i) { console.log("onmouseover", d, i); },
	       onmouseout: function (d, i) { console.log("onmouseout", d, i); }
	   },
	   gauge: {
	       label: {
	           format: function(value) { return value; },
	//            show: false // to turn off the min/max labels.
	       },
	//    min: 0, // 0 is default, //can handle negative min e.g. vacuum / voltage / current flow / rate of change
	   max: 300, // 100 is default
	   units: ' V',
	//    width: 39 // for adjusting arc thickness
	   },
	   color: {
	       pattern: ['#FF0000', '#F97600', '#F6C600', '#60B044'], // the three color levels for the percentage values.
	       threshold: {
	           unit: 'value', // percentage is default
	//            max: 200, // 100 is default
	           values: [30, 60, 200, 199]
	       }
	   },
	   size: {
	       height: 90
	   }
	});

	setTimeout(function () {
	   chart.load({
	       columns: [['data', 10]]
	   });
	}, 1000);

	setTimeout(function () {
	   chart.load({
	       columns: [['data', 50]]
	   });
	}, 2000);

	setTimeout(function () {
	   chart.load({
	       columns: [['data', 70]]
	   });
	}, 3000);

	setTimeout(function () {
	   chart.load({
	       columns: [['data', 299]]
	   });
	}, 4000);


	</script> 
</body>
</html>