Category Archives: Linux

Time based access control with iptables, cron and at

Until today I handled scheduled internet access for my daughters devices via my Apple AirPort Extreme that is configured as a bridge between my wired and my wireless network at home.

This setup has worked flawlessly for quite some time. There is one catch to this set up though. Each time I want to make an exception to the time based internet access rules I need to reconfigure and restart the AirPort Extreme. The restart takes a minute or two during which there is no wireless network for anyone at home. I guess that you can relate to the sheer panic that occurs in our home during that time.

The router/firewall/server/etc that I run at home is a Ubuntu 16.04 box running on a physical machine with two network cards. This machine now handles the time based internet access.

I decided to use iptables, cron and at in a small shell script, that you can find at the end of this article, since they are all proven tools that I am familiar with.

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How to block unwanted ads and malware in all applications

*update: Wednesday, 2 March 2016. Switched back to the hosts file from because that one has a more adequate size and therefore much better performance. The file from uses to much memory if you run a local resolver on your machine.

*update: Wednesday, 17 February 2016 rewrote the script with additional error checks after comment from Peter. Now there is only one script with the hosts file from

*update: Tuesday, 16 February 2016 added another script that also cleans OS X 10.11 DNS caches and uses an even more extensive hosts file from

Recently I compared adblock+, ghostery and a bunch of other ad blocking software in the browsers that I normally use. Most of them blocked ads really well but unfortunately all of them added quite a lot of additional CPU and memory overhead. So, despite the fact that these programs help me to speed up my browsing experience by eliminating advertisements they still slow down my browsing experience.

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Check for available patches in Ubuntu via cron

I have been thinking about writing a small script that checks if there are available patches for my machines for a long time. Never got around to do it until today and it proved to be easier then I thought.
Just add the following script to your cron-tab and the system will send you email when there are patches available for your system.


HOWTO: Disable pulseaudio in Ubuntu

This has been tested on Ubuntu 12.04.1 and 12.10 x86_64

I got myself a USB DAC and a set of nice headphones for Christmas. One of the main concerns was that the new hardware must work with Linux since Linux is my main OS at home. As it turns out most USB DACs work out of the box with Linux as they are standard USB compliant sound devices.

All modern Linux distributions seem to use pulseaudio as a front-end for ALSA these days. The thing that pulseaudio does is to remix all audio streams in software which is a bad thing if you have some nice audio gear that probably can do this much better.

The following explains how to uninstall pulseaudio and to configure ALSA on a per user basis. It also explains how to up-sample your audio from spotify, deadbeef, vlc and so on via ALSA.

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