Building GHDL on Ubuntu 18.04

GHDL is an open-source simulator for the VHDL language. GHDL allows you to compile and execute your VHDL code directly in your PC. The latest stable release is version 0.36. Documentation and “getting started” can be found here.

To download the source code and switch to the right tag use following commands:

git clone
git checkout tags/v0.36

Install some requirements using apt:

sudo apt install gnat libz-dev

Now you can configure, build and install the simulator:

./configure --prefix=/usr/local/
sudo make install

Installing Redis on Debian 9

Redis is an in-memory key-value store known for its flexibility, performance, and wide language support.

Installation is very easy considering that it is provided by apt:

apt install redis-server

After installation Redis will be running as a service. You can use these commands to check the status, or start and stop:

service redis status
service redis start
service redis stop

Or the systemctl version:

systemctl status redis
systemctl start redis
systemctl stop redis


Using the command “redis-cli” you get a command line prompt. The following commands will show you the basic functionality of your Redis server:

# redis-cli> ping
PONG> set test "Is it working?"
OK> get test
"Is it working?"> exit

Installing Mosquitto on Debian 9

MQTT or Message Queuing Telemetry Transport, is an ISO standard (ISO/IEC PRF 20922) publish-subscribe-based messaging protocol.

Mosquitto by Eclipse is an open source implementation of an MQTT message broker. It currently implements MQTT protocol versions 5.0, 3.1.1 and 3.1. It’s lightweight and suitable for use on all devices from low power single board computers to full servers.

Installation is very easy considering that it is provided by apt:

apt install mosquitto

After installation Mosquitto should be running as a service. You can use these commands to check the status, or start and stop:

service mosquitto status
service mosquitto start
service mosquitto stop

Or the systemctl version:

systemctl status mosquitto
systemctl start mosquitto
systemctl stop mosquitto

Testing your installation

To test our new installation we need to install a few extra packages:

apt install mosquitto-clients

To subscribe to topic1 subtopic2 we use the following command:

mosquitto_sub -v -t "/topic1/subtopic1"

In an other console session you can then enter following command to publish a message to this subtopic:

mosquitto_pub -m "test message" -t "/topic1/subtopic1"

If the message is received in your first session your MQTT installation is working as intended. By default mosquitto listens on all interface. To only allow traffic from localhost add “bind_address localhost” to “/etc/mosquitto/mosquitto.conf” and restart the service.

Captain Kirk is a Pirate!

Last week (Thursday October 18th) I visited the European Parliament. There was an event there called “Science rules!”. This event featured veteran Start Trek actor Walter Koening (aka Pavel Chekov), several real live European Astronauts and the scientific advisor to commission president Barosso. As a long time space fanatic and Star Trek fan this was an event I could not miss.

Amongst others Belgian astronaut Frank De Winne

At some point during the discussions a scientist uttered her frustration about budget cuts and that Captain Kirk would never be recalled because of budgetary reasons. Stressing that it was only a fictional series. This is however completely wrong.

In the Star Trek universe power is generated using a matter-antimatter reaction. Engines powered in this way can generate a tremendous amount of energy. This energy people onboard the Enterprise can us to make anything the need in their day to day live using their replicators. So they live in a world of abundance. There is no scarcity.

Tea, Earl Grey, Hot!

This is why there is no money in the Federation and all of this is made possible by technology. Thought experiments like this are a big part of what make science fiction and Star Trek interesting and important in our society.

Nowadays technology to store, transmit and process information is increasing faster than humanities collective ability to create more information. So Today all our cultural and scientific works are only scarce because of the laws our politicians make or maintain.

This doesn’t mean they have an infinite amount of power available to them. It can certainly run out when going at high Warp for long time or when powering the shield in heated battles. It just means there’s more than enough to keep everybody living comfortable all of the time.

So I would like to ask all of our lawmakers to not make us all turn into Ferengi, to please not recall captain Kirk and boldly go!

Youtube released censored video

Earlier I wrote an article on a video that has been removed from Youtube on request of the Belgian national railroad operator (NMBS). This video showed someone protesting the strikes by making a fake announcement on a train. On the 25th of March the owner of the blocked account notified me with good news. After a review Youtube decided that the video in question was not in violation of the “Youtube’s community guidelines”.

That Youtube restored the situation is obviously a good thing. However there is still is something fundamentally wrong with the attitude Youtube takes in cases like this. There is an important principle in modern democracies that was not respected by Youtube, “The Presumption of Innocence”. A better procedure for Youtube to follow would be to properly examine any claim before taking video’s offline. This approach would be more just.

Youtube might have serious faults in it’s policies. The real vital question is why would the NMBS do this? It suffers no commercial damage from this video. It can’t suffer any commercial damage at all considering it has a monopoly on passenger transport in Belgium. It might have suffered some image damage from this action. But it obviously suffers considerably more image damage from the strikes itself. To my knowledge there has never been any attempt to silence the strikers.

I think our government should investigate from who within the NMBS the action to take down this video originated. It’s obvious that this person has no respect for the right to freedom of speech. A reprimand for this person seems in order.