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My random knot in the Web


This is my home in the virtual world, where I write about things that I want to share. The freely available software that I've written as well as some of the photographs I've taken over the years can also be found here. Please use the navigation links on the right if you are looking for something.

Recent articles

  1. Updating FreeBSD from source

    Sometimes I need to update my FreeBSD operating system. I prefer to do that from the source code, so that my customizations in (/etc/src.conf) remain.

    At the writing of this article, I'm tracking the 10-STABLE branch. To start this, I removed the contents of /usr/src and ...

  2. Switching IPython to Python 3

    More and more, IPython has become my tool of choice as the ultimate calculator and to try out concepts and code for use in my programs.

    While I generally use the terminal-based interactive shell, notebooks offer more capabilities for integrating text, formulas and graphics.

    With Python 2.7 effectively mostly ...

  3. Making saline solution

    The standard recipe for saline solution is 9 grams of salt per liter of water.

    Since most people don't have an accurate scale, we need to convert the nine grams to a volume. For that we need the bulk density of table salt. For fine table salt, the listed ...

  4. Modifying a FreeBSD port

    Installing software on FreeBSD is made easier by the ports system; a collection of Makefiles and patches that contains instructions on how to build programs and libraries. E.g. building and installing the mpv media player is done in the following way:

    # cd /usr/ports/multimedia/mpv
    # make install clean ...
  5. TeXcalc

    As an engineer, I often do diverse calculations that I want to save in my logbooks which I write in LaTeX. Up to now I've either formatted those by hand or used the listings package to include calculations made in IPython.

    These techniques are not optimal. Formatting by hand ...

  6. Stltools

    From the release of version 3.2, the py-stl software has been renamed to stltools. The reason I made this change mostly has to do with how FreeBSD handles packages. Programs that require an interpreter are prefixed with its name and version. So py-stl would become py27-py-stl, which would be ...

  7. Generate random passwords

    One way of making hard to guess passwords is to take random data and encode it with base64 to make it readable. This is what I've done in the script.

    This is mainly useful for passwords that you can store in a secure manner (like in an ...

  8. Repairing a color laserjet 2550

    Some time ago, my trusty old color laserjet 2550L more or less stopped printing, or at least I thought so. It turned out that the printer only printed in yellow. Which is not particularly useful.

    At the time I bought this printer not because I print very much, but because ...

  9. Installing OpenProject on FreeBSD

    At work we want to run OpenProject. But since this a ruby-on-rails app and installation on Windows is not supported, I volunteered to set up a dedicated FreeBSD server for it.


    The server install was a basic FreeBSD 10 install done via the memory stick image. On the harddisk ...

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