dimitris kalamaras

mathematics, social network analysis, free software…

Tag: Debian

How to get free signed SSL Certificates and setup secure domains in Apache and Debian

This how-to describes the process to obtain 100% free, signed SSL Certificates from StartSSL.com and configure Apache in Debian to use these SSL certificates in your virtual domains, so that people can access your site(s) through https (i.e. https://example.com) without ever having the browser tell them the scary “this site isn’t trusted” anymore.

Before you start, you will need:

  • One or more of your functional domains which point to a server you own and have root access to. In this tutorial I’ll be using my wife’s supersyntages.gr as testbed.
  • A browser, for this tutorial Chrome, although you might prefer Firefox (see below why).
  • Root access to your server with Debian and Apache installed, with the above domains configured as VirtualHost.
  • The openssl package installed in your computer.
  • One of the following emails configured in each of the domains you want to include in the SSL certificates:
    [email protected]
    [email protected]
    [email protected]

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SocNetV 0.51: changes, new logo, and RPM packages

Last Friday, I released version 0.50 of Social Networks Visualiser (SocNetV) and version 0.51 followed already (yesterday), fixing an important (and yet embarrassing) bug in Graph::createDistanceMatrix() method.

IMHO, this new version is the first really usable version of this little application. With it you can draw mathematical graphs (social networks, to be precise, since the focus is more on Social Network Analysis than on Graph Theory), by pointing and clicking, load existing networks of most popular formats (Pajek, GraphML, GraphViz, UCINET, etc), create random networks (Small Worlds, Erdos-Renyi, Ring Lattices, etc), compute actor centralities (Betweeness, Closeness, Graph, etc) and clustering coefficients, select a different network layout based on these centralities (or Spring-Embedder models), and finally export your work to PDF, BMP or PNG file formats, without crashes (unlike earlier releases). A complete workflow, that is!

I am really proud of this progress (if not amazed) since I didn’t expect it to come this far 5 winters ago when I was playing with Qt toolkit while I was on army service in Evros 🙂 Yet, this application has really evolved in my spare time, and seems to be useful to some people (mostly academia).

To celebrate this new release, I prepared RPMs for both Fedora 10 and openSUSE 11.1 distros. Serafeim Zanikolas maintains already an older .deb package in Debian ‘experimental’ (and soon in Sid), while Markos Chandras just added SocNetV to qting-edge overlay, which also houses all new Qt4 and KDE4 software. Ubuntu users may add my Launchpad PPA (older version) to their repos or opt to compile from source (it’s really easy!). Meanwhile, 0.51 is the first version for which we provide a Windows zipped archive with executables (although I cant say I really tested it :P)…Oh, and we now have a much more polished and ad hoc logo (handmade with Gimp/Inkscape of course):

Nice, isn’t it? 😛

Math and Algebra software you can’t miss in Linux…

Yesterday, I was searching for some nice mathematics applications, mainly for computer algebra, in Linux and here are my two main conclusions.

  • First, there are hundreds of math programs and libraries out there for any need!
  • Second, try to stick with Debian-based distros, or else you ‘ll end up compiling the universe.

In the beginning, I had not exact idea what I was searching for, but to be honest I would love to have something like Mathcad (which unfortunately is commercial and not open-source). Unfortunately, I don’t believe there is such thing in Free Software, at least for the moment.

Nevertheless, after a little search with apt-cache (using Debian unstable), various applications came to my attention.

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