revontulet.dev

Installing Arch from Arch onto an External Drive

Fri, 30 Jan 2026 10:00:00 +0000

To install Arch Linux, the most common and easiest way is booting it up from an installation media. This may not be an option, and instead we want to install it straight onto a drive. The Arch Wiki provides a guide to Install Arch Linux from existing Linux, but it took a while to get all pieces right. Consider this post to aim for a more noob-friendly and handholding setup on how to install Arch from Arch. For readability, only hyperlinks not referring to wiki.archlinux.org are marked with their source in brackets.

No Shave November Through the Eyes of Face Detection

Sun, 30 Nov 2025 08:00:00 +0000

Every year No Shave November and Movember are held to raise funds and spread awareness for Men’s Health, particularly cancer research and treatment. They are more or less the same, but not exactly. Movember vs No Shave November (tue.nl) provides a more detailed view of their differences. The idea is simple: Do not spend your money on a barber for the whole of November, instead donate it to a good cause.

Wayland, Sway, Nvidia DLSS, Unreal Engine and Ghosting

Sat, 15 Nov 2025 10:00:00 +0000

Since January 2023, I’m the owner of a Steam Deck. Until April 2025, my main computer still had Windows running, but I found that I hardly use it for anything but the browser and games. Given the Steam Deck experience, I was confident to ditch Windows and continue playing on Linux from here on. Especially as pretty much anything I play is on Steam. However, in my setup with an Nvidia RTX 3070 and Sway (thus Wayland), heavy ghosting occurred on games like Hogwarts Legacy, and one I started most recently, Arc: Raiders. Overall, these problems seem to happen with games that are built in Unreal Engine, as e.g. RDR2 or GTA V work flawlessly.

Don't Let Your Mocks Mock You!

Fri, 12 Sep 2025 10:00:00 +0000

Here’s a short one about a pattern that we can unfortunately too often observe when it comes to mocks. Especially with databases, we see our “Repository” or “Database Connection” mocked out in tests. That is, for the sake of unhappy path testing. However, more often than not we also see that these mocks are used for happy path testing.

There is a real danger where our mocks are mocking us.

The Hidden Cost of Slow Feedback Loops

Sun, 17 Aug 2025 10:00:00 +0000

This post has been lying around as an idea for a couple of months now. A list of bullet points on my computer is from somewhere mid-June, and I originally intended to title it “The Underappreciation of Fast Feedback Loops”. However, calling out a cost sounds catchier and is more accurate, because we do not only underappreciate them, but they cost us. First and foremost, nerves (because who likes to wait for results?), but moreover do slow feedback loops actively reduce delivery speed of teams.

AI-first - We're just 6 months away from AGI ;-)

Sat, 31 May 2025 10:00:00 +0000

The ~~Matrix~~ AI is everywhere. It is all around us. Even now, in this very room. You can see it when you look ~~out your window~~ something up on the internet or when you turn on your ~~television~~ washing machine. You can feel it when you go to ~~work~~ do anything nowadays… when you go to ~~church~~ a search engine… when you ~~pay~~ fill out your taxes. It is the world that has been pulled over your eyes to blind you from ~~the truth~~ meaningful content.

iPhone Ethernet bridge on RaspberryPi with Ubuntu Server

Sun, 11 May 2025 08:00:00 +0000

This post covers how to tether your iPhone via USB to your RaspberryPi, and share the iPhone’s network on eth0. Eventually, the RaspberryPi will be connected to a router via ethernet, making the router use the iPhone’s internet connection. A RaspberryPi 4B is used, but this guide should work on other models too.

One may wonder why this setup is needed. Routing at least DNS traffic through the Pi with the Pi-hole is a common use-case, but all traffic less so.

Arch and i3 - Hello, Sway! - Install Arch and Sway

Wed, 26 Mar 2025 18:00:00 +0000

Welcome to part one of the three-part series “Hello, Sway!” The series is split into

Arch & Sway setup using archinstall
Sway Configuration
Linux QoL Tools

Motivation

For a while already, there has been no real reason for me to keep Windows. The doubt started about two years ago, in January 2023, when I got myself a Steam Deck. Although the purchase was mostly to emulate console and handheld games, of course the question was “But Can It Run Crysis?” To my surprise, the games I tried performed incredibly well, almost all of them out of the box. Thanks to ProtonDB, if there was a title that needed some extra configuration, it is usually there.

Hello World

Sun, 16 Mar 2025 00:00:00 +0000

Welcome to revontulet.dev!

So … what is this about?

Introduction

My name is Matthias Döpmann. I’m a Software Engineer, originally from Germany, nowadays located at the Arctic Circle in Finland. There is no specific content for this blog. At the time of writing, I host a couple of articles on MisterDerpie.com, that I intend to migrate over to this blog.

There were several reasons I stopped writing on the old blog. The first is, that whilst living in Dublin and working for Amazon/Amazon Web Services, I was fairly occupied by work and rarely found motivation to follow up on these topics besides work. Second, in 2022, the world at Amazon was still remote, so on top of that I spent a lot of time travelling. Moreover, instead of reading computer science/software engineering books, I spent a good chunk studying languages (actual languages, not Programming Languages). These days I’m taking courses in Finnish, so I am not sure how much time is left to actually dump content here, but let’s see! Ultimately, the non-integration of the old blog with GitHub Actions or the like set the bar higher to publish contentent. Although I dockerized the process of rendering the blog, uploading it to an FTP after the render was still too annoying (… and yes, whilst I could have automated that, I didn’t). Checking out a GitHub repository, write down some thought, and then just hit git commmit and git push is just a lot more convenient.

Ubuntu with WSL2 and i3 Window Manager GUI

Sat, 04 Dec 2021 19:00:00 +0000

Using i3 and Ubuntu native is probably best, but you may not get the choice to do so, in case your working machine is running Windows. I looked through several guides how to set up Ubuntu with i3 on WSL2, but it took me several hours to get the setup I looked for because things did not work as expected. Therefore I’m writing this guide.

Installing Ubuntu on WSL2

There are plenty of tutorials and videos to do so. I will refer to the very one that I used to set up the bare, GUIless minimum, WSL2 Ubuntu GUI by David Bombai. Reproduce the steps until Install Ubuntu GUI (7:25) to get the headless Ubuntu on WSL2 up and running.

Ubuntu and i3 on Lenovo Legion 5 Pro

Sun, 22 Aug 2021 15:00:00 +0000

During my summer vacation, I got myself a Lenovo Legion 5 Pro, powered by an AMD Ryzen 7 5800H and an Nvidia RTX3070. Though this post is not about the legion, I have to say it is an awesome laptop. What this post is about is how to make Ubuntu with i3wm run on the Lenovo Legion.

Installing Ubuntu

Create Bootable USB Media

You need a USB stick as well as a Ubuntu ISO image. Plenty of tutorials exist on the web to create a bootable Ubuntu USB stick. Ubuntu.com provides official documentation, coming from a device running Windows, Ubuntu or Mac OS X.

Generics - Invariance, Covariance and Contravariance

Sun, 04 Jul 2021 22:00:00 +0000

In my previous post I stated that I am currently reading Kotlin in Action (2017, Manning). In chapter 9, the authors introduce generics in Kotlin. My overall experience with generics in Java is good, but apparently that book taught me something completely new. The concept of Covariance and Contravariance was something unknown to me. This post, though categorized Kotlin, focuses more on the concepts in general, yet will demonstrate them in Kotlin. I assume the reader has a basic understanding of generics and inheritance.

Teststubs with Kotlin Extensions

Fri, 25 Jun 2021 22:00:00 +0000

The repository with the Kotlin code can be found on github/MisterDerpie/kotlin-data-stubs.

Currently I’m having the great luck that our team started using Kotlin at work. For that reason, I decided to learn Kotlin properly and started my journey with Kotlin in Action (2017, Manning). This is a bit outdated, considering that Kotlin 1.5 is the current release, but the vast majority of concepts are the same as for 1.0.

One concept that fascinates me and I really see a lot of value in is Extensions. Especially for tests I find that concept very useful, because it enables us to provide test related logic to our classes without actually adding this in the real production code. Let’s have a look at how we can utilize extensions to create stubs of business classes.

Spring Boot with MongoDB

Wed, 26 May 2021 22:00:00 +0000

The sourcecode of this post is available on github/MisterDerpie/spring-boot-with-mongodb.

Foreword

For a small application to store receipts I wanted to use Spring Boot and NoSQL database MongoDB. As with many basic topics in the spring world, there is a Getting Started guide on spring.io, with the specific title “Accessing Data with MongoDB”.

Though this guide may suffice for a really straightforward start, it actually misses out two, from my point of view, essential questions.

RaspberryPi 4 as a remote Multimedia Station

Sun, 02 May 2021 17:00:00 +0000

Foreword

Since many years I am using JDownloader as the solution to download things on all my computers. The problem with it is though that the files are not synchronized between them. Thus I cannot access what I downloaded from any machine different from the original downloader. This problem worsens even with the fact that once I am not at home, I cannot access the harddrives the multimedia is on.

Create a blog using Jekyll and Docker

Sat, 24 Apr 2021 20:00:00 +0000

Foreword

~~This blog is created using Jekyll.~~

The striked through sentence above used to be true for the old version of this blog, hosted on [misterderpie.com]. However, the version at [revontulet.dev] uses GitHub pages and Hugo.

Original Post

I really like Jekyll, as I don’t like frontend development. One problem is though, that I currently only have Jekyll installed on one single machine. So when I’m not at home but want to add a blog post, I would have to install Jekyll on the machine I’m travelling with. Luckily there is Docker and the envygeeks/jekyll-docker Jekyll Image. As I’m adding blogposts very rarely, I do not need to have a full build and delivery pipeline for it (despite the fact that at the time of writing I wouldn’t even be able to create such). A simple container to build the latest version of the site suits my needs.

Read Temperature & Humidity with RaspberryPi 4 - Docker Setup

Wed, 31 Mar 2021 22:00:00 +0000

In my previous post, I showed how to enable the Raspberry Pi 4 on Ubuntu Server to read out DHT11/DHT22 sensor data. But this is a very hacky solution. Moreover is the Raspberry Pi cluttered with some stuff, that we may need to configure differently for another setup or remove as a whole. It’s a nice coincidence that I’m currently reading Docker in Action, Second Edition (Manning, 2019), so I wanted to build a docker image to read out the data. There are some images available for this already, but I still wanted to build my own light-weight image.

Read Temperature & Humidity with RaspberryPi 4

Sun, 21 Mar 2021 11:00:00 +0000

I recently bought a RaspberryPi 4 and installed Ubuntu Server 20.04 64 Bit on it. There are many tutorials available how to read the temperature/humidity via Python, unfortunately none of them worked out of the box. It seems to be that they are

either for Raspbian OS
or for 32 Bit OSes.

After some searching I found a way from several sources to make it run. This is a horrible hacky workaround and I’d be very happy to see a better way and/or out-of-the-box solution.

About Me

Sun, 06 Mar 2022 00:00:00 +0000

To be populated :-)

Search

Mon, 01 Jan 0001 00:00:00 +0000

revontulet.dev

Installing Arch from Arch onto an External Drive

No Shave November Through the Eyes of Face Detection

Wayland, Sway, Nvidia DLSS, Unreal Engine and Ghosting

Don't Let Your Mocks Mock You!

The Hidden Cost of Slow Feedback Loops

AI-first - We're just 6 months away from AGI ;-)

iPhone Ethernet bridge on RaspberryPi with Ubuntu Server

Arch and i3 - Hello, Sway! - Install Arch and Sway

Motivation

Hello World

Welcome to revontulet.dev!

Introduction

Ubuntu with WSL2 and i3 Window Manager GUI

Installing Ubuntu on WSL2

Ubuntu and i3 on Lenovo Legion 5 Pro

Installing Ubuntu

Create Bootable USB Media

Generics - Invariance, Covariance and Contravariance

Teststubs with Kotlin Extensions

Spring Boot with MongoDB

Foreword

RaspberryPi 4 as a remote Multimedia Station

Foreword

Create a blog using Jekyll and Docker

Foreword

Original Post

Read Temperature & Humidity with RaspberryPi 4 - Docker Setup

Read Temperature & Humidity with RaspberryPi 4

About Me

Archives

Search