Offline videos are available here:
https://video.fosdem.org/2026
It's organized by room which you can find here: https://fosdem.org/2026/schedule/tracks/
It's organized by room which you can find here: https://fosdem.org/2026/schedule/tracks/
I'm gonna summarize the Varlink talk: DBus is, and I quote, "very very very complex" and his system with JSON for low-level IPC is, in fact, the best thing since sliced bread and has no significant flaws. It works basically just like HTTP so the web people will love it. Kernel support for more great shit pending! I'm not sure where the hardon for a new IPC system with lernel (keeping that typo) support is from, but he's been trying for 15 years now. AFAICT, the service discovery problem could be solved by a user space service without much trouble. I mean if the whole thing wasn't an exercise in bad technological taste.
If anything, that talk was a tad low effort, with even dismissive answers — "Yes" and "No?" as full answers to audience questions, with no follow up?! Still very informative though!
It's a very "I've made a cool thing. This is what I think is cool about it" type of talk. Which I don't think is uncommon for FOSDEM. Maybe a bit uncommon for a higher profile figure like Lennart.
He held a similar talk at All Systems Go I think (I missed the talk here at FOSDEM).
> It's a very "I've made a cool thing. This is what I think is cool about it" type of talk.
Varlink isn't something he just made up, he mearly "adopted it" (started making use of it). It existed before, but I don't know anything that really made use of it before.
The official-looking website at https://varlink.org doesn't give any information about who the authors are, as far as I can tell, but the screenshots show the username "kay". There's a git repo for libvarlink [1] where the first commits (from 2017) are by Kay Sievers, who is one of the systemd developers.
An announcement post [2] from later in 2017, by Harald Hoyer, says that the varlink protocol was created by Kay Sievers and Lars Karlitski in "our team", presumably referring to the systemd team.
So the systemd developers "adopted" their own thing from themselves?
[1]: https://github.com/systemd/systemd/commits/main/?author=kays...
[2]: https://github.com/search?q=repo%3Asystemd%2Fsystemd+varlink...
If Lennart Poettering "adopted" varlink, he seems to have done so from members of his own team ("our team") who created varlink and who are also fellow co-creators of systemd.
Varlink is based on much more conventional UNIX technology than Dbus, which is decades old: You connect to a named UNIX socket through its socket file in the filesystem (man page: unix(7)).
This is an old mechanism and it is known to work well. It does not require a broker service, it works right at system startup, and it does not require a working user database for permission checks (which would be a circular dependency for systemd in some configurations). If at all, I am surprised that systemd didn't use that earlier.
The main thing that Varlink standardizes on top of that is a JSON-based serialization format for a series of request/response pairs. But that seems like a lightweight addition.
It also does not require kernel support to work, the kernel support is already there. He mentioned in the talk that he'd like to be able to "tag" UNIX sockets that speak varlink as such, with kernel support. But that is not a prerequisite to use this at all. The service discovery -- and he said that in the talk as well -- is simply done by listing socket files in the file system, and by having a convention for where they are created.
Though I have a pretty good idea of where a Varlink broker would turn up and which init system it would be tied to.
You can run "netstat --listening --unix" to list the UNIX domain servers on your system, to get an impression.
You can see the progress schedule here: https://review.video.fosdem.org/overview
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