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Start OpenHAB on Raspberry Pi in Debug Mode

When you need to start OpenHAB in debug mode, the standard approach is to run the script But on the Raspberry Pi (i.e. on Debian) this script does not exist. Instead you need to edit the file /etc/default/openhab that contains an entry DEBUG=no, which needs to be changed to DEBUG=yes.

Watching Log Files on Linux/Unix

Most people I come across use tail -f fileName to watch files. The drawback, however, is that for a closer inspection of something I had just seen, I have to abort this and change to some file viewer (where I first need to find again what I want to check). So why not use a single program that can do both things? less fileName does this for you. What many seem to be unaware of, is that less has a built-in tail mode that can be activated with Shift-F and left with Control-C. Once back in normal view mode again, it is very easy to scroll up a few lines and inspect the interesting part of the file. And once finished, you can just press Shift-F again and are back to tail mode.

Upgrade MQTT Broker Mosquitto on Raspberry Pi: “The following packages have been kept back”

While exploring MQTT I had installed the Mosquitto message broker on my Raspberry Pi. However, the version that is in the Debian Wheezy repository is, as of this writing, really old (v0.15). So an upgrade was in order and fortunately the guys from Mosquitto have set up a Debian repo of their own and a description how to use it.

But on my system I then got the following message:
xxx@yyy:/etc/apt/sources.list.d# sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  mosquitto mosquitto-clients
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.

The general recommendation to solve this is run
sudo apt-get dist-upgradeI did not want to do this for various reasons. So the approach I took instead, was to simply remove the old version with sudo apt-get remove mosquitto mosquitto-clients and re-install it, then taking the new version from the Mosquitto repo sudo apt-get install mosquitto mosquitto-clientswhich worked nicely for me.

Xubuntu Window Title Bars Gone

I have an old machine running Xubuntu 12 and quite like it. But the shutdown from the UI sometimes does not work. One possible consequence is that after the next start the window title bars are gone, as was in my case the widget to switch virtual desktops. To get this fixed a simple
rm -r ~/.cache/sessions/
is enough.

Introduction to 3D Printers

Here is a video I came across recently, which I liked and wanted to share.

Jez Humble on Continuous Delivery

I recently stumbled over this video. It gives a good introduction to what Continuous Delivery is at its core.

Canadian Army Disassembles and Reassembles Jeep in Under 4 Minutes

The title says it all, enjoy!

VMware Fusion 4 on OS X Mavericks

Having upgraded to OS X Mavericks just recently, one of the main questions for me was, whether I would need to upgrade from VMware Fusion 4 to the current version (which is Fusion 7). Initially the thought had not really occurred to me, but after the second crash of my MacBook I started to look around. The majority of content I found was about the support status and some people had gotten really agitated during the discussion. But little was said about the technical side of things, i.e. whether the stuff was working or not.

What I can say today is that for me VMware Fusion 4.1.4 works nicely and without issues so far. I use it almost exclusively to run a company-provided Java development environment on Windows 7 64 bit. So no 3D graphics, USB drives, or other “fancy” things.

The crashes were most like caused by an old version of the keyboard remapping tool Karabiner (formerly KeyRemap4MacBook). Once I had upgraded to the appropriate version, the crashes were gone.

Ant Build System for the Nullsoft Installer System (NSIS)

Lately I had to automate the installation of quite a few inter-related system components for the creation of demo systems (usually in virtual machines). In my case those were  a dedicated database, three server applications and various clients operating against those servers. The important part was that quite a few configuration settings had to be aligned across all these components. So I decided to externalize those settings into a common properties file and build wrappers around the original installers that would query that properties file.

Since this was a Windows-only exercise I decided to leverage the Nullsoft Installer System (NSIS) which is free and has a great community with loads of additional plugins. But for building my installers I still used Ant to achieve this automatically and therefore reproducibly. Other factors were

  • Support for arbitrary number of components with quick and easy addition of new ones
  • Wherever possible automate also the download of the original installers
  • As “centralized” as possible, meaning that only component-specific aspects should be handled outside the main NSIS script

The result is a central NSIS script that includes component-specific details. Those are post-processing instructions and the original installers. Overall, it was worth the effort and provided a robust basis for other similar setup later on.

Connecting to Raspberry Pi via SSH: Connection Timeout

When trying to connect to my new Raspberry Pi via SSH, this only worked when done locally. It turned out to be caused by the /ect/hosts file. I had set the hostname using the raspi-config tool, which linked it with the loopback address instead of the real one (192.168.x.x). Changing it to the proper address solved the issue.