www.rolfje.com

Reading an ISKRA AM550 P1 Port with a Pi

Jan 17, 2020 · 3 min read · environment ·
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Although I am the guy with a soldering iron and a bit of software development experience, I am not a fan of the "internet of things", "smart meters" or smart anything really. Not because I don't like technology, but because of the potential security and privacy problems it brings with it. That said, …
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Logging in with SSH certificates

Jun 18, 2019 · 3 min read ·
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Suppose you want to provide ssh access to a server or machine without having to change the server configuration for each new user that requires acces, there is a very nice feature in ssh called "SSH Certificates". This blogpost explains a simple setup to get you started. Creating the Certificate authority …
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Travis CI and Dependabot added to Anonimatron

Apr 26, 2018 · 2 min read · Anonimatron security Utilities ·
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With new European rules like the GDPR and local variations like the Dutch AVG, interest in Anonimatron is increasing. Although I do not keep track of who is using it and where, sometimes new requirements do pop up. Recently a feature was added to Anonimatron 1.9.2 to also anonymize files. In the wake of those …
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1N4148 diode as RF switch

Feb 24, 2018 · 4 min read · hamradio Hardware technology ·
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For a recent experiment I was using BA389 PIN diodes to switch low power RF signals. I was asked why I didn't use an ordinary 1N4148 for that. Since I didn't know what an 1N4148 would do when used like that, and I also didn't really know what a BA389 actually does, I decided to do some measurements.Aren't diodes …
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Even geen donor meer

Feb 14, 2018 · 4 min read · opinion ·
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"Niertransplantatiefietsen" worden ze onder artsen wel eens genoemd. Tot nu toe had je grote kans dat je de nieren, longen of andere organen van deze gezonde motorrijder had kunnen ontvangen. Zodra ik me mocht registreren heb ik gelijk aangegeven dat ik volledig donor wil zijn. Omdat ik niet geloof in leven …
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Interdigital Bandpass for RTL2832U Receiver

Feb 9, 2018 · 4 min read · hacking hamradio ·
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Building a receiver for a voice repeater system in this area I set up a thumbsat receiver connected to a Raspberry Pi. The receiver is part of the repeater system to widen it's receiving range. However, the performance turned out not to be too optimal. I guessed that the GSM and Wifi signals around here could cause the …
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JSON alerts for Munin

Jan 7, 2018 · 3 min read · monitoring munin Ubuntu Utilities ·
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Munin is a great and easy way to monitor your servers. The documentation for Munin is kind of all over the place, and sometimes not all that clear. * There is the recent ["Munin Guide"](https://munin.readthedocs.io/en/latest/) which is quite informative and well laid out. Sometimes additional info and …
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Fixing a Jenkins 1.5 Slave on Windows 2016

Jan 1, 2018 · 1 min read · jenkins programming ·
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When you configure a Jenkins 1.5x slave on a Windows 2016 machine according to the instructions on wiki.jenkins-ci.org you will probably get a warning that the .Net 2.0 is not available. This is reported as issue 21484 and the fix is to upgrade, which sometimes can be a problem. If you can't upgrade to the latest …
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Mattermost Delete Channel "fixed"

Oct 26, 2017 · 4 min read · hamradio programming security usability ·
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Users of Mattermost have probably noticed the less-than-optimal interface design where de Delete option is right above the Leave option in the Channel menu. On a busy server, you can imagine having quite a few incidents where people accidentally completely delete a channel. In the Open Source version of Mattermost, …
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Installing GPG keys for Debian Backports

Jun 9, 2017 · 2 min read · Debian linux security ·
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For Let's Encrypt to automatically renew certificates on your Raspberry Pi, you probably want to install certbot. The installation instructions of certbot tell you to make use of the Debian Backports packages. Following the instructions to install backports packages into apt-get on raspbian (which is a Debian Jessie), …
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