FOSDEM 2025

Why do you go away? So that you can come back. So that you can see the place you came from with new eyes and extra colors. And the people there see you differently, too. Coming back to where you started is not the same as never leaving.

~ Terry Pratchett

This weekend I had opportunity to attend to legendary FOSDEM 2025 conference. Pure fun experience - could met lot of technology freaks, get inspired by some talks and all of that enjoying nice Belgium beer 🍺

Fun things I’ve learnt

• There is a tool called Volkswagen that makes all of your failing CI green. It was made after Volkswagen was caught on cheating on some tests
• There is a tool called git-muzak that fetches music you are currently listening and adds it to your commit message
• There is a lot of controversy around systemd and its said that creator Lennart Poettering was receiving death threats due to not following UNIX philosophy 😅
• It’s been a while I was doing CTFs - sqlmap is really poweful tool! It solved a problem within seconds while I was struggling to craft correct sql injection for long time.
• I’ve heard an interesting hypothesis that some premium services on airports like fast security check without a queue or VIP lounge with free food and drinks can be accessed by everyone by just modifying the QR code with your boarding pass . Like the whole validation was about checking if there are right bytes on the right place, without any validation if this passenger really has access to these services. If it was real it would be really crazy, wouldn’t be?!
• There is a way to hack office box and send letters for free. Just write STS in top right corner and it will be treated as student to student letter - you don’t need pay for it. We live in an interesting world!

Some comments on talks I’ve seen

State of OpenJDK

Link to talk

I haven’t been following what happens in Java world lately and that presentation did a good job summing up what are current direction.

I liked the format:

Pain point → Competitors (what languages are doing better than Java) → What is currently happening in this area.

Some of pain points mentioned:

• Verbosity
• Java is hard to pick up by newcomers
• Slow startup times

Tightening every bolt (curl creator)

Link to talk

Talk given by the living legend - curl creator. How cool is that to say my project has been downloaded much more than 20 000 000 000 times, is being run on every device on the planet Earth and Mars. Super impressive and inspiring!

He talked about his day to day struggles working on project on which so many depends. Cool thing that burned in my mind was extensinve amount of jobs in CI that helps in daily work like taking care of consistent documentation .

Build a Great Business on Open Source without Selling Your Soul

Link to talk

I think it’s a super tricky thing to earn money from open source that’s why I decided to spend some of my time listening about this issue. We know all these horror stories with evil companies that change license and take projects over - is it even possible to avoid such situations?

Three strategies were mentioned:

• Creating things around opensource like learning about tool (taking advantage that youre an expert)
• Commercial version that extends open source (like DBeaver does) - it also sounds pretty fair
• Helping others in hosting open source project

I this that it must be very satisfying way of living to give away something for free to community and simultaneously earn money on some additional activity.

Implementing a rootless container manager from scratch

Link to talk

This guy blown my mind.

I wanted to understand well what happens when I run container, so I decided to write my own software that does exactly that. Also, I needed something lightweight for my other open source project. Thats how lilipod happened.

Presentation delivered really well, from showing how images are structured in layers so it’s easy to deduplicate them (and download only what’s needed) through mounting user to root of container to limiting syscalls that can be invoked and other things that make containers secure. Really enjoyed this one!

How browsers REALLY load Web pages

Link to talk

Speaker was exposing some inconsistencies across three major browsers: Chrome, Firefox and Safari. Audience could learn how to set priorities of resources (images, scripts, css) which browsers load during rendering page and that it’s almost impossible to deliver the same experience in all these browsers, because they differently interpret these priorities.

I liked the way it was being presented - whole presentation was made in clown theme - the deeper we were going, the speaker had more clown attributes which I really liked and it well resonated with content of presentation. It’s insane that we have so many standards to do one thing like fetching resources during page rendering (ye, ye, I know it’s much more complex than it looks to be 🤣).

14 years of systemd

Link to talk

Maybe I’m lame but before I came to this talk I didn’t know that something like systemd even exists (and is such crucial in most of linux distros!).

It was hard for me to understand what was the purpose of this talk. Creator of systemd bragging how great systemd is and that there won’t be rewrite of it in Rust. Beside he also shared some difficulties project encounters and how they try to figure out these.

Fullness of room wasn’t helpful - atmosphere was really sleepy there!

Zero-Code Distributed Traces for any programming language

Link to talk

First of all - I didn’t have a clue that something like eBPF exists. As far as I understood - linux kernel offers an interesting event-driven api that invokes your code whenever some low level operation happens.

For example you can do some operations whenever tcp packet arrives (or goes out).

Few approaches were presented how it can be leveraged to instrument code in any language without having to write a single line in code. Just add eBPF to your node and enjoy your trace spans appended in headers.

Also some approaches without eBPF were presented. It was one of the best presentation I’ve seen during this FOSDEM.

I loved trials and errors approach of speaker and great sense of humor!

O11y-in-One: Exploring a Unified Telemetry Database

Link to talk

There is no silver bullets, but… clickhouse almost is - well, I was hoping to learn about some useful observability technology but what I heard was a buy our tool it’s awesome talk.

Qlafoutea: Baby steps towards compiling a programming language to analog quantum computer

Link to talk

I know nothing about quantum computing that’s why I thought that it would be nice opportunity to learn at least some high level concepts. Especially that there was “baby steps” in title of presentation. Speaker started from super simple statements but I think I missed something fundamental because I still didn’t get the idea. I think that steps weren’t that baby!

I’ve got an impression that quantum computing it is still crawling and from my perspective I won’t be able to make anything useful with it for now (still don’t get why would I like to have a program that returns inconsistent results - probably I’m missing something 😅)

CLI Design for Designers and Developers

Link to talk

Not what I expected, but quite refreshing.

There is a lot talks about Design in context of frontend apps: what makes beautiful UI beautiful and usable etc.

It was first this kind of talk about CLI I saw - what makes CLI usable, why it’s challenging and why it differs from UI design. How hard it is to keep it consistent and introduce some standards that all CLIs would follow.

Speaker was well prepared and it was pleasure to listen about his perspective on this problem.

Lessons learned Open Sourcing the UK’s Covid Tracing App

Link to talk

I was there by accident but so many cool issues where raised there!

How to deal with hate, when you’re spending public money on project and people disagree with your decisions?

The proposed solution was to share your reasoning behind decisions you make so people don’t think that it was random. I think that’s useful not only in open source projects ;)

How to explain people that are not techy what’s an open source? And how to explain conspiracy theories fans that comment TODO: cure covid they found in source code is just a not funny joke made by programmer who thought it would be funny? At this moment he said that he’s glad they didn’t have comments like this:

/* after receiving terminate signal kill all the children and spawn new daemon */ that could be found in some low level applications 🤣

Wrapping up

Had I learnt some new shiny technologies or some fundaments I’ve been building for years were destroyed?

Nope.

Have I been inspired and got some fresh ideas I want to play with?

Hell yea!

Looking forward to FOSDEM 2026 👋🏻