Stable releases, with security support

I run Linux in lots of places, from remote servers/VMs, to my house router, to my desktop/laptop. Some of those I don t want to be updating regularly with new software releases, I need something I can be sure is going to keep working, but will get necessary security + critical updates. A rolling distro that provides security via the latest upstream release doesn t provide that guarantee. Equally there need to be regular stable releases, or things become too stale. (The one time I considered moving away from Debian was during the 3 year Sarge / 3.1 release cycle. I think if things hadn t improved I d have jumped ship to Ubuntu at the time.)

A good selection of packages

One of the reasons I moved from RedHat to Debian was the wide range of packages available as part of the standard OS. Pulling it all into the distro helps with quality control, compared to random 3rd party packages. A centralised bug system and repository is a win too. Perhaps packages at all is something I should list, but I take it as a given if you re running a distro. I need to know what I have installed on my machine, what version that software is, what files it owns, and what it depends on.

Free Software

This is important to me. I ll make pragmatic compromises about software I run on my systems if it makes sense, but I want to start from a place that does not require anything non-free. I ve run a company on Debian, and I ve worked on numerous products that ran it under the hood. The DFSG give me confidence I can do that.

Smooth upgrades

Debian s ability to upgrade a system smoothly is one of the reasons I first moved to it. The first upgrade I did was remotely on a machine sitting on a 2Mb/s leased line. I was nervous doing the reboot at the end, but it came back fine. At the time the equivalent procedure with RedHat involved rebooting into the OS installer to do the upgrade.

I know things have moved on since then, and really it should all be scripted, and machines should be cattle not pets, but for personal use I run a small enough number of machines that having the upgrade path between releases is a must have.

Community

The original pull of the Debian community was the knowledge I could get involved, and upload packages that were missing that I was using. That s how I first got involved, uploading things Black Cat used, which made life easier for us in the long run. I don t have time to maintain all the software I use myself, and I don t want to be beholden to a commercial entity to do so for me, so a distribution that allows me to help out where I can as part of the community seems to me to be the right way to do things.

Architecture support

Perhaps less important, especially when I started using Debian, but these days I have amd64, arm64, armhf, and riscv machines. Everything except for the risvc box is doing something useful, and would need replaced if I couldn t keep running it, and I expect RISC-V to transition into that state in the next few years as the hardware improves.

Binary packages

I ran a FreeBSD desktop for some time. It might have been the way I was holding it, but binary package installs were generally not something reliable, especially after the initial install, and I ended up building things from ports from source quite often. That worked incredibly well (I used to think people who raved about Gentoo really should just go do it properly and use FreeBSD), but I don t want to spend time compiling things, especially on some of my machines (my router should not need a compiler, for example).

Why LLMs are so deceptive The output of an LLM often looks very compelling, professional and correct. Humans have evolved to trust or distrust new information based on easy to detect secondary factors like what authority the speaker holds, or how confidently and eloquently the message is conveyed. Humans are however very bad at fact-checking and cross-referencing new information, as it requires a lot of effort, and humans like saving energy and being as lazy as possible.

Information asymmetry The less you know about something, the easier it is to fool you on that topic. Nobel prizes in economics have been given in for research on how information asymmetry distorts markets and leads to suboptimal outcomes. In the field of software engineering we have now witnessed a flood of aspiring software developers using AI to create software that looks like it might work, but that is actually full of flaws. These people are well-intended, but they simply lack the expertise to understand what they are actually doing, and don t possess the necessary judgement to decide when an LLM spits out something truly useful and when it is creating mostly garbage. This asymmetry in expertise I think explains the majority of the conflict currently witnessed in open source projects the senior developers are flooded with requests to review code that is bad and a waste of time for everyone involved, while availability of AI grows the pool of people who could contribute and create more code slop at an ever-increasing speed. The information asymmetry could to some degree be evened out if seniors teach juniors to do software engineering well, but it is of course not feasible to quickly mass educate everyone. Also, it seems that many don t want to learn but instead expect to have all understanding outsourced to LLMs. Many seniors have noticed this and have stopped teaching juniors as the seniors don t like the feeling of having their time wasted by teaching people who don t want to learn. Juniors probably all understand that it would be better to learn to design and write software yourself, but using LLMs just feels too easy. I can fully relate to why people choose to take the path of least resistance. Unfortunately, that path often leads to a dead end.

Humans fall too easily for anthropomorphism The human brain is wired to think that inanimate objects are alive and have feelings. Small children talk to their stuffed animals as if they were real, and lots of adults experience feelings of things happening in their surroundings due to some acts of gods or elves being angry or whatever. When we see a machine writing just like a human, or even more convincingly hear it talk and respond to our talk like a living thing, our brain automatically starts assuming it is a living thing with intelligence and feelings. The fact that these creatures live in the abstract cloud and only appear through a portal we hold in our palm and behave in a way that was designed for maximum engagement makes the illusion even stronger. I recommend people try out running LLMs locally on their laptop to see the raw thing spitting out tokens and have some of the illusion shattered. Also stop saying please to an LLM. It does not have any feelings.

Understanding temperature In my experience understanding the concept of temperature in LLMs helps see why an LLM might confidently generate a plausible-looking but totally wrong code change. The large language models are statistical machines that, based on the input (previous tokens) to the neural network, try to predict what to output (next token). When running an LLM, if the temperature is configured to be zero, the output is very predictable and always follows the paths of the strongest connections (a.k.a. weights) between nodes and layers of the neural network. Unlike in living creatures where the brain learns and changes all the time, the weights of an LLM can only change during training. When an LLM is in normal use (during inference, generating next tokens) the weights are fixed, and if temperature is zero, the answer to a specific question will always be exactly the same. This is of course a bit boring and too machine-like, so typically LLMs have a bit of temperature set, which introduces random variation in what connections the neural network traverses. Again, I recommend people try running small LLMs locally where temperature and other settings are fully exposed and configurable to see this themselves. It is a good antidote to falling for the illusion that LLMs would actually be intelligent.

Why benchmarks don t tell the whole story If LLMs continue to produce so much garbage, why are benchmarks showing that they are constantly improving? AI models are indeed improving all the time. For example the CAIS AI dashboard visualizes how frontier models have evolved in the past few years. However, the best models still have a pass rate of only about 50% on the Humanity s Last Exam. On SWE-bench the best model today resolves just under 77%. That means there is a significant number of times when the AI is wrong. This matches my personal experiences, and the renowned Greg Kroah-Hartman recently wrote on the Linux developers mailing list that even with the best of the current and next generation tools, at least 1/3 of the results they generate are flat out wrong or harmful . When generating cat videos the error rate does not matter, but in engineering, things absolutely must be correct. Sure, humans also make mistakes, but well educated and properly incentivized humans are so much more capable than LLMs in many regards. We can achieve complex things that work reliably, such as operating worldwide commercial air traffic without planes falling down every day. There are currently a lot of humans who are incentivized to maintain the narrative that general artificial intelligence is coming soon and will take over everything. In fact, the whole financial system is currently skewed towards such a vision because the promise of falling labour costs and increased profits and monopolistic control of everything attracts capital like nothing before. In this environment we need to remember that machines and economic systems are ultimately servants of humans, and not the other way around.

It s just a tool LLMs are not a scam, but a useful tool and technology that has its uses. But the idea that AI has or will surpass humans any time soon in either capabilities or efficiency is simply not true, and we should listen to the people who created humanity s so far most complex systems (computers and software), who are saying that LLMs are in many cases so bad, that it might be better to ban them in certain places completely for the time being than to waste far more valuable human time on reading the text and code they generate. The time asymmetry is not a new phenomenon as there has been various script kiddies for a long time. As an example, a person running a memory leak scanner without understanding the results and spending 10 minutes to file a bug report could force an open soruce maintainer to spend an hour on proving and explaining that the finding is false. What is new is how much the AI users blindly trust the outputs they get, and open source is uniquely vulnerable as there are no managers protecting developers use of time.

What I do, recommend, and expect to see in the next stages I am using AI tools daily, and constantly experimenting with new models and new ways to use them. Sometimes they work, and often they don t. Sometimes looping AI on itself can make it fix its own errors, but sometimes it just gets derailed and will never arrive at the correct solution. When an LLM fails to make a calendar entry for the right time based on reading my email it is easy for me to spot that it is wrong. I try to avoid using LLMs for anything where I can t exercise judgement myself on whether the result was correct or not. I also really hope that other people would not send me anything where their own effort was less than the effort I have to make reading and understanding it. This principle is not new many have heard the requirement that reading code must require less effort than what it took to write it. I have always kept a high bar on software code and asked fellow developers to make sure their code is well structured, easy to follow and documented. LLMs unfortunately make it easier for people to cheat in this regard, but if cheating is easier, maybe the punishment and deterrence needs to be higher now too. Now with many open source projects adopting policies that put guardrails on AI use, I expect we will soon start witnessing cases where the policies are enforced and it will be interesting to see how violations are judged. As a society we might also need to develop new social standards and rules in what is acceptable treatment of other humans in human-to-machine interactions, and perhaps also new standards in showing what humans are responsible for what machine as the machines start acting more and more independently. I encourage people to take part in these discussions, and in case of doubt, err on the side that favors real human interactions. Contrary to what many business people seem to think, and even though I am in general a techno-optimist myself, I don t feel there is any need to rush with AI adoption.

Changes in prrd version 0.0.7 (2026-08-27)

• Updates to DESCRIPTION have been made as CRAN requirements change
• The continuous integration setup was updated several times
• The database connection now uses sqliteSetBusyHandler

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can sponsor me at GitHub.

In 2025 I was honored to be selected for the first cohort of Sovereign Tech Fellows, a program by Germany s Sovereign Tech Agency to improve the resilience of the open source ecosystem by supporting maintainers directly (complementing their existing support for larger FOSS organizations). Back in 2025, I was only working very limited hours however, this has changed in 2026.

For the second half of 2026, I am working again as a Sovereign Tech Fellow, but this time with significantly increased hours. After finishing my PhD, I do have time now for new tasks (and new jobs!), and the fellowship presents an amazing opportunity to really advance projects that I maintain or am part of. This also has a very nice effect on contributors and bug reporters, as their feedback gets addressed a lot faster. With some luck, this ultimately will help finding new (co)maintainers for projects as well (although in the age of AI, a lot of how open source used to work is much more uncertain, but that is a matter for a different blog post).

The fellowship is time-limited, so I am intending to make the time I currently have count!

So, what s planned?

I am involved in many projects, but three of them will be getting attention as part of the fellowship. I know I am notoriously slow at blogging, but expect more details on each of them very soon. Here s an overview:

Freedesktop.org, Specifications and Organization

I maintain the Freedesktop Specifications, which is an area of Freedesktop that has traditionally been a bit chaotic. This worked in the past, because Freedesktop was never intended to be a formal standards body, but more a shared space where people could throw a lot of code and ideas over the wall and see what sticks and what people can collaborate on.

While I very much love the spirit of this and want to keep it in some form, we definitely would benefit not just from more formalization and better procedures, but also from better organization of the specifications in general. A lot of conflicts can be avoided by that. I will work on improving procedures, crunching through the (lots!) of pending bug reports and MRs, and to make the specifications site better searchable and accessible (similar to how Mozilla s MDN presents information, but I am not sure if we will get quite that far). I also intent to add a compatibility matrix for specifications, so if a desktop opts out of any one of them (or does not implement them yet) that fact is documented and authors of applications know what they can expect. This will allow us to move a lot faster and avoid a lot of conflict, because there is no implicit assumption that everybody will implement everything anymore (which has never been quite true anyway).

Hopefully, this will ultimately result in a Freedesktop that is both a lot more useful for application authors who want to bring their project to Linux, as well as developers of desktop environments who need to see which specifications are available and which ones are current.

In addition to that, I have also worked on a Freedesktop.org website refresh, which is pretty much done in its first iteration (pending sysadmin action). The aim there is to have a more official website, separate from user-contributed wiki content, that showcases what Freedesktop is and which projects are using it for hosting. Once the new website is live, I will also review every page again, archive dead projects in their own section and reorganize the software and specifications directory. Those sections are severely outdated and are missing recent efforts from the community, while still containing long-dead old projects (remember HAL? ).

AppStream

A lot of extra maintenance work will be (has been!) done on it. This includes things such as JPEG-XL support (blog post soon), sandboxed media processing, support for newer specification additions, better OARS integration (and potentially migrating it to fd.o infrastructure), improvements and API stabilization for libappstream-compose and a lot of bugfixing and resolution of issues found by AI code review.

AppStream was originally designed to parse only trusted data from vetted Linux distribution sources this is no longer the case in today s world and in the way Flatpak uses it, so we need to increase resilience of the project.

I am also exploring a project that could vastly improve search accuracy for AppStream. Stay tuned for that.

PackageKit & System Upgrades

Many years ago, people thought we would all migrate to atomic Linux distributions and slowly not need PackageKit anymore. This has not turned out to be the case, and there are still plenty of reasons to use a package-based OS, especially in development environments. At the same time, PackageKit has been basically the same for years, and its older architecture is beginning to show. It being a daemon who s literal job it is to modify the entire system also makes it one of the most security-sensitive components that a Linux system can have, while simultaneously making it near-impossible to sandbox.

My plan is to create PackageKit 2.0 by building on the great foundation of PackageKit 1.0, but modernizing it. This will include simplifying its code and removing a bunch of features that have no more use in modern desktops, while also adding some features that PackageKit never had but that would be useful to expose to frontends (still no to interactivity an terminal-progress forwarding though!). PK 2.0 will also allow me to solve a few design issues that have been worked around in the past, by replacing them with better solutions. This will be a painful transition, as PackageKit 2.0 will break all interfaces PackageKit has and those interfaces have been frozen for more than a decade. However, I do fully expect this change to be worth the effort.

In addition to that, I intend to look into the offline-update procedure again and improve it. The current multi-reboot operation comes with downsides, that newer systemd features such as soft-reboot can alleviate. The end result should be a much smoother, less annoying offline-update experience for users (I especially want to get rid of updates running on system startup, which I consider quite bad from a usability perspective). The new behavior is in the early drafting stages and may need direct support from systemd. I will share more about it once I can.

That s a lot of tasks!

Yes! I will see how far I get. I am moving project-by-project though, to allow me to focus on one project at a time, rather than scattering my attention continuously. Amazingly, this means that the major tasks for AppStream are already almost done, and we are nearing the 1.2.0 release. AppStream got priority, because the new Freedesktop Flatpak runtime will be released soon, and because I want FlatHub/Flatpak to have access to the new AppStream release sooner. Freedesktop and PackageKit are next on the task list.

Either way, a lot of progress is coming if you have any feedback or want to help out, please don t hesitate to reach out! All work is happening fully in the open, so you can also chime in on the respective GitHub/GitLab tasks .

You can also expect blog posts about key features or interesting changes, so stay tuned!

:demo
A1 @0,0 prio=4096
A2 @0,1
A3 @0,2
A4 @0,3
B1 @1,0 prio=8192
B2 @1,1
B3 @1,2
B4 @1,3
C1 @2,0 prio=8192
C2 @2,1
C3 @2,2
C4 @2,3
A1 -- A2 hazard=0
A2 -- A3 hazard=0
A3 -- A4 hazard=0
B1 -- B2
B2 -- B3
B3 -- B4
C1 -- C2 hazard=0
C2 -- C3 hazard=0
C3 -- C4 hazard=0
A1 -- B1 cost=10
B1 -- C1 cost=10
A4 -- B4 cost=20
B4 -- C4 cost=20
Leo @-0.3,0.7 proto=none icon= 
Mia @-0.3,1.3 proto=none icon= 
Joy @0.3,0.7  proto=none icon= 
Roy @0.3,1.3  proto=none icon= 
A2 -- Leo hazard=0 A2:edge
A2 -- Mia hazard=0 A2:edge
A2 -- Joy hazard=0 A2:edge
A2 -- Roy hazard=0 A2:edge
Max @-0.3,1.7 proto=none icon= 
Zoe @-0.3,2.3 proto=none icon= 
Ada @0.3,1.7  proto=none icon= 
Amy @0.3,2.3  proto=none icon= 
A3 -- Max hazard=0 A3:edge
A3 -- Zoe hazard=0 A3:edge
A3 -- Ada hazard=0 A3:edge
A3 -- Amy hazard=0 A3:edge
Eli @0.7,0.7 proto=none icon= 
Jay @0.7,1.3 proto=none icon= 
Kai @1.3,0.7  proto=none icon= 
Ben @1.3,1.3  proto=none icon= 
B2 -- Eli hazard=0.2 B2:edge
B2 -- Jay hazard=0.2 B2:edge
B2 -- Kai hazard=0.2 B2:edge
B2 -- Ben hazard=0.2 B2:edge
Ava @0.7,1.7 proto=none icon= 
Lea @0.7,2.3 proto=none icon= 
Ivy @1.3,1.7  proto=none icon= 
Rex @1.3,2.3  proto=none icon= 
B3 -- Ava hazard=0.2 B3:edge
B3 -- Lea hazard=0.2 B3:edge
B3 -- Ivy hazard=0.2 B3:edge
B3 -- Rex hazard=0.2 B3:edge
Ana @1.7,0.7 proto=none icon= 
Eve @1.7,1.3 proto=none icon= 
Abe @2.3,0.7  proto=none icon= 
Ian @2.3,1.3  proto=none icon= 
C2 -- Ana hazard=0 C2:edge
C2 -- Eve hazard=0 C2:edge
C2 -- Abe hazard=0 C2:edge
C2 -- Ian hazard=0 C2:edge
Ned @1.7,1.7 proto=none icon= 
Lou @1.7,2.3 proto=none icon= 
Fay @2.3,1.7  proto=none icon= 
Sue @2.3,2.3  proto=none icon= 
C3 -- Ned hazard=0 C3:edge
C3 -- Lou hazard=0 C3:edge
C3 -- Fay hazard=0 C3:edge
C3 -- Sue hazard=0 C3:edge

The basics Designed in the 80s, the spanning tree protocol has evolved into a rapid flavor (RSTP) and a VLAN-aware variation (MSTP).² Any sound-minded network engineer knows there are better alternatives, like BGP EVPN VXLAN. Yet, because any switch speaks it, the venerable spanning tree protocol still fills a niche. We focus on RSTP: it replaced the original protocol in 2004. To eliminate network loops, RSTP implements a complex state machine. Timers, link state changes, and the link-local control frames a bridge receives from its neighbors drive its transitions. These Ethernet frames are the Bridge Protocol Data Units (BPDUs). You can watch them in action below: hit the Start button.

:protocol rstp
:tx-hold 10
A1 @0,1
C11 @1,0 prio=4096 icon= 
C12 @1,2 prio=4096 icon= 
C21 @2,0 prio=4096 icon= 
C22 @2,2 prio=4096 icon= 
A2 @3,1
H1 @0,0.2 proto=none icon= 
H2 @0,1.8 proto=none icon= 
H3 @3,0.2 proto=none icon= 
H4 @3,1.8 proto=none icon= 
A1 -- C11
A1 -- C12
A2 -- C21
A2 -- C22
C11 -- C12
C11 -- C21
C11 -- C21
C11 -- C22
C12 -- C21
C12 -- C22
C21 -- C22
A1 -- H1 A1:edge
A1 -- H2 A1:edge
A2 -- H3 A2:edge
A2 -- H4 A2:edge

After some time, the topology converges to a tree: from the root C11, there is a path to each bridge³ and no loop. In the upper right corner, the interface displays a tree icon followed by the time it took to reach this state. Cut a link and see how the protocol finds an alternate path to reach C12 in less than a second. You can stop the simulation, move it forward step by step, reset it to its initial state, or slow it down with the snail mode . Don t worry about all the displayed information: I explain it later.

Note While you scroll, the current simulation stays in view so you can look at it while reading. Uncheck this box to disable this behavior: .

All examples run in your browser, powered by MSTPD an open-source user-space⁴ implementation of RSTP.⁵

Historical interlude Radia Perlman, an inductee of the Internet Hall of Fame in 2014, summarized the ancestor of STP she invented at DEC with this poem, later included in a US patent:

I think that I shall never see
A graph more lovely than a tree.
A tree whose crucial property
Is loop-free connectivity.
A tree which must be sure to span
So packets can reach every LAN.
First, the root must be selected.
By ID, it is elected.
Least cost paths from root are traced.
In the tree, these paths are placed.
A mesh is made by folks like me,
Then bridges find a spanning tree. Radia Perlman, Algorhyme.

Electing the root bridge To build a tree, RSTP first elects the bridge with the lowest bridge identifier as the root bridge. The bridge identifier combines the priority and the MAC address: 8192.6e:2b:10:a0:5f:29. In the example below, S1 and S2 have priorities of 4,096 and 8,192: S1 becomes root. S4 has a priority of 12,288, while S3 keeps the default priority of 32,768:⁶ S4 becomes root. S5 and S6 don t have a specific priority, so the lowest MAC address wins and S5 becomes root.

:protocol rstp
S1 @0,0 prio=4096
S2 @0,1 prio=8192
S1 -- S2
S3 @1,0
S4 @1,1 prio=12288
S3 -- S4
S5 @2,0
S6 @2,1
S5 -- S6

Initially, each bridge advertises itself as root:⁷

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    Root Identifier: 8192.02:00:00:01:00:01
    Bridge Identifier: 8192.02:00:00:01:00:01

Once a bridge receives a BPDU advertising a better root bridge, it propagates this new information to its neighbors.

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    Root Identifier: 4096.02:00:00:00:00:00
    Bridge Identifier: 8192.02:00:00:00:00:01

Assigning roles to ports The second step is to assign a role to each port. RSTP defines five roles, each denoted by a letter:

• root (R),
• designated (D),
• alternate (A),
• disabled (X), or
• backup (B).⁸

Each non-root bridge chooses its root port, the one with the lowest-cost path to the root. Unless you override it, each bridge derives the link cost from the speed: 20,000 for 1 Gbps. In case of equality, the lowest port identifier wins. Each remaining port becomes a designated port if the BPDU it sends is better than the BPDU it receives. Otherwise, it becomes an alternate port. Later, if the root port goes down, the best alternate port becomes the new root port. The tiebreakers for the best BPDU are:

1. the lowest root bridge identifier,
2. the lowest accumulated cost to the root,
3. the lowest bridge identifier, and
4. the lowest port identifier.

:protocol rstp
S1 @1,0  prio=4096 icon= 
S2 @0,1
S3 @2,1
S1 -- S2
S1 -- S3
S1 -- S3
S2 -- S3

In the example above, after convergence, S1 is the root bridge because it has a priority of 4,096, while the other bridges have a priority of 32,768. All its ports are designated ports because the accumulated cost to the root is 0. S2 s port facing S1 becomes a root port because it has the lowest accumulated cost to the root 20,000 vs 40,000. S3 has two ports facing S1, and the one with the lowest port identifier becomes the root port 0x8000 vs 0x8001. The other candidate is an alternate port because the remote port on the link sends a better BPDU, with an accumulated cost of 0. On the segment between S2 and S3, S2 s port wins: while both bridges have the same accumulated cost to the root (20,000), S2 s bridge identifier is smaller 32768.02:00:00:00:00:01 vs 32768.02:00:00:00:00:02.

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    Root Identifier: 4096.02:00:00:00:00:00
    Root Path Cost: 20000
    Bridge Identifier: 32768.02:00:00:00:00:01
    Port identifier: 0x8002

If you cut the active link between S1 and S3, S3 promotes the best alternate port to root port. If you also disable the second link, S3 chooses the remaining alternate port as a root port. But if you disable the link between S1 and S2, S2 needs a bit more work to elect a new root port because it does not have an alternate port. Unless a specific event happens, designated ports send BPDUs every 2 seconds.⁹ If a bridge does not receive BPDUs from its neighbor for 3 consecutive hello periods, it considers the neighbor dead and removes the port information.

Port state transition Each port can have one of three states. The diagram displays a background color for each state:

• discarding (red),
• learning (yellow), or
• forwarding (green).

A root port transitions automatically to the forwarding state. An alternate port stays in the discarding state. A designated port has two options to transition from the discarding state to the forwarding state:

• If the port is an edge port, either through configuration or because the remote device does not speak any flavor of STP, the bridge assumes the device won t participate in the protocol and cannot create a loop. In this case, the designated port immediately transitions to the forwarding state.
• Otherwise, it sends a proposal to its downstream neighbor. If the remote bridge agrees that the received BPDU is better than any other BPDU stored for other ports, it elects the receiving port as its root port and starts the synchronization process: it transitions all non-edge non-synced designated ports to the discarding state to avoid a loop. Then, it sends back an agreement. Upon receiving the agreement, the peer designated port transitions to the forwarding state.¹⁰

:protocol rstp
S1 @1,0 prio=4096 icon= 
S2 @1,1
S3 @0,2
S4 @2,2
S5 @0,3 prio=8192 icon= 
S6 @2,3
H1 @0,1.2   proto=none icon= 
H2 @2,1.2   proto=none icon= 
H3 @2.5,1.3 proto=none icon= 
H4 @2.5,2.3 proto=none icon= 
S1 -- S2
S2 -- S3
S2 -- S4
S3 -- S5
S4 -- S6
S4 -- S3
S5 -- S6
S3 -- H1 S3:edge
S4 -- H2 S4:edge
S4 -- H3 S4:edge
S6 -- H4 S6:edge

In the topology above, H1, H2, H3, and H4 are end devices not participating in the protocol. We configure the ports they connect to as edge ports, so these ports immediately move to the forwarding state. Use the step button to move the simulation forward. The clock moves to 1 second. Step again and S1 and S2 send a proposal to each other. Here is the proposal from S2:

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x4e, Agreement, Port Role: Designated, Proposal
        0... .... = Topology Change Acknowledgment: No
        .1.. .... = Agreement: Yes
        ..0. .... = Forwarding: No
        ...0 .... = Learning: No
        .... 11.. = Port Role: Designated (3)
        .... ..1. = Proposal: Yes
        .... ...0 = Topology Change: No
    Root Identifier: 32768.02:00:00:00:00:01
    Root Path Cost: 0
    Bridge Identifier: 32768.02:00:00:00:00:01
    Port identifier: 0x8001

S1 ignores it: its own root identifier is lower. When S2 receives a similar proposal from S1, it accepts S1 as its root bridge. It also elects the port to S1 as the root port and starts the synchronization process. The two designated ports are already discarding, so no change here. Step again and S2 sends two BPDUs to S1. In one of them, the agreement bit is 1 and the proposal bit is 0. It also shows that S2 accepted S1 as the root bridge and its root port is now in the forwarding state. When receiving this BPDU, S1 transitions its own designated port to the forwarding state. From this point, the link between S1 and S2 forwards user traffic.

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x79, Agreement, Forwarding, Learning, Port Role: Root, Topology Change
        0... .... = Topology Change Acknowledgment: No
        .1.. .... = Agreement: Yes
        ..1. .... = Forwarding: Yes
        ...1 .... = Learning: Yes
        .... 10.. = Port Role: Root (2)
        .... ..0. = Proposal: No
        .... ...1 = Topology Change: Yes
    Root Identifier: 4096.02:00:00:00:00:00
    Root Path Cost: 20000
    Bridge Identifier: 32768.02:00:00:00:00:01
    Port identifier: 0x8001

Let s look at what happened to S5. Reset the simulation and step twice. S5 exchanges BPDUs with both S3 and S6. Since S5 has a lower root identifier than S3 and S6, it stays the root bridge, while S3 and S6 accept the proposal and elect their root ports. S3 and S6 start the synchronization process. S6 s port to H4 keeps forwarding because it is an edge port. Move one step. Both S3 and S6 send an agreement back to S5, which transitions both designated ports to the forwarding state. Yet, the link between S5 and S3 keeps discarding user traffic! If you look carefully, S3 s port toward S5 is now a designated port, not a root port. During the same step, S3 also receives a better BPDU from S2 with S1 as the root bridge. It elects its port to S2 as the root port and downgrades the port to S5 to a designated port, which stays in the discarding state. On the next step, things get a bit tricky. S3 sends a proposal to S5:¹¹

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x4f, Agreement, Port Role: Designated, Proposal, Topology Change
        0... .... = Topology Change Acknowledgment: No
        .1.. .... = Agreement: Yes
        ..0. .... = Forwarding: No
        ...0 .... = Learning: No
        .... 11.. = Port Role: Designated (3)
        .... ..1. = Proposal: Yes
        .... ...1 = Topology Change: Yes
    Root Identifier: 4096.02:00:00:00:00:00
    Root Path Cost: 40000
    Bridge Identifier: 32768.02:00:00:00:00:02
    Port identifier: 0x8002

S5 elects S1 as its root bridge and the port toward S3 as its root port. It starts its synchronization process, but the designated port to S6 does not move into the discarding state. Why? That port stays a designated port and its neighbor S6 has already sent an agreement on the link, so the port keeps its synced status. Now, let s step back to look at what happens to S6. At this point, S6 believes S5 is the root bridge. Step once and S4 sends a new proposal to S6. S6 accepts the proposal, elects S1 as the root bridge and the port to S4 as its root port. The role of the port facing S5 changes: from a root port, it becomes a designated port. Because its peer keeps advertising an inferior BPDU on the link, this port becomes disputed and moves to the discarding state. The root port transitions to the forwarding state and the link starts forwarding immediately because S4 s designated port is already in the forwarding state. If we step one more time, S5 and S6 exchange two BPDUs. The one from S5 is better because of its lower bridge identifier. S5 s port stays a designated port, while S6 downgrades its own port to an alternate port. Let s rewind to the start one last time: cut the link between S1 and S2, run the simulation until the topology is stable, stop the simulation, and restore the link between S1 and S2. During the first step, S1 and S2 exchange proposals. S2 elects S1 as the root bridge instead of S5 and the port to S1 as the root port. It downgrades the previous root port to a designated port and moves it into the discarding state. The other designated port stays synced and keeps its forwarding state. At the next step, S2 sends an agreement to S1 and the link between them starts forwarding user traffic. It also sends a proposal to S3, but not to S4. Instead, it sends a regular BPDU to S4. S4 still elects S1 as its root bridge and the port to S2 as its root port. It demotes its previous root port, the one to S3, to a designated port, which transitions to the discarding state because of the root port change. The other alternate port, to S6, also becomes a designated port and stays in the discarding state. The new root port moves to the forwarding state. On the next step, S4 s port to S3 settles as an alternate port after receiving a better BPDU from S3. RSTP is a giant state machine split into smaller ones: bridge detection, port information, port protocol migration, port role selection, port role transitions, port receive, port state transitions, port timers, port transmit, and topology change. Some of them are per bridge, some per port. Each bridge runs an instance. Time, operational port state changes, and the BPDUs it receives from other instances drive the transitions. Being event-driven makes RSTP more efficient but also more difficult to understand.

Placeholder for the Port Information state machine extracted from IEEE 802.1Q-2005, page 182. Pending IEEE authorization for reproduction, this is the blueprint for the Western Australian Government Railways class Msa Garratt articulated steam locomotive.

Topology change notification A bridge populates a MAC address table: it associates each source MAC address with the port that last received it. When forwarding an Ethernet frame, it looks up this table to choose the right port.¹² When a link fails, a connected fridge reachable through one port may become reachable through another one. The affected bridges should flush the MAC addresses they learned, because these entries may now be wrong. For this purpose, RSTP implements topology change notifications using a flooding mechanism. When a non-edge port transitions to the forwarding state, a bridge generates BPDUs with the topology change (TC) bit set. It sends them to all the non-edge designated ports and to the root port. It also flushes the MAC address table on these ports. When a bridge receives such a BPDU, it propagates the notification to all non-edge designated ports and the root port, except the one the notification came from. It also flushes the MAC address table on these ports. In the examples, the BPDUs with the TC bit set to 1 have a red circle.

:protocol rstp
S1 @1,0 prio=4096 icon= 
S2 @0,1
S3 @1,1
S4 @2,1
S5 @1,2
LPT @0.1,2 proto=none icon= 
S1 -- S2
S1 -- S3
S1 -- S4
S2 -- S3
S2 -- S5
S4 -- S5
S5 -- LPT S5:edge

Start the simulation and wait a few seconds for the topology to settle. Stop the simulation and disable the link between S2 and S5. S5 elects the port facing S4 as the root port, which transitions immediately to the forwarding state. Step once and S5 emits a BPDU with the TC bit set to 1:

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x79, Agreement, Forwarding, Learning, Port Role: Root, Topology Change
        0... .... = Topology Change Acknowledgment: No
        .1.. .... = Agreement: Yes
        ..1. .... = Forwarding: Yes
        ...1 .... = Learning: Yes
        .... 10.. = Port Role: Root (2)
        .... ..0. = Proposal: No
        .... ...1 = Topology Change: Yes
    Root Identifier: 4096.02:00:00:00:00:00
    Root Path Cost: 40000
    Bridge Identifier: 32768.02:00:00:00:00:04
    Port identifier: 0x8002

S4 receives this BPDU. It flushes the MAC address table on the port facing S1: while LPT was previously reachable through this port, it is now reachable through S5. Step once. S4 sends S1 a BPDU with the TC bit set to 1. When S1 receives this BPDU, it flushes the MAC address table on the ports facing S2 and S3. Step once and S1 sends a notification to S2 and S3. Step once again and S2 sends a notification to S3, while S3 does nothing because the port toward S2 is an alternate port. S3 does not flush any MAC address table: LPT is still reachable through its port to S1. If you step a bit more, you will see that some of the periodic BPDUs keep the TC bit set to 1. Each port runs a timer equal to the hello timer plus one second.¹³ The timer starts when the port emits a notification. Until it expires, the port sets the TC bit to 1 in every BPDU it sends. You can also see some periodic BPDUs without the TC bit: they originate from a port that only received a notification and therefore did not arm its timer.

Security RSTP is weak against configuration errors and malicious actors. A bridge not talking RSTP can create a loop. An attacker can insert themselves into the topology to disrupt the service, spy on the traffic, or alter it. To mitigate such problems, you need to identify the edge ports. An edge port connects to an end device, like a PC or a printer. Such devices do not generate BPDUs and cannot create a loop. RSTP defines two related flags:

• When true, AdminEdge initializes a port as an edge port. It defaults to false.
• When true, AutoEdge lets a port become an edge port when it does not receive BPDUs for 3 seconds. It defaults to true.

If an edge port receives a BPDU, regardless of the values of these two flags, it reverts to a non-edge port.

R0 @1.5,1.5 prio=8192
# AutoEdge=true, AdminEdge=false, bridge
S1 @3,1.58
R0 -- S1
# AutoEdge=true, AdminEdge=false, end device
H1 @2.84,2.18 icon=  proto=none
R0 -- H1
# AutoEdge=true, AdminEdge=true, bridge
S2 @2.18,2.84
R0 -- S2 R0:edge
# AutoEdge=true, AdminEdge=true, end device
H2 @1.58,3 icon=  proto=none
R0 -- H2 R0:edge
# AutoEdge=false, AdminEdge=true, bridge
S3 @0.68,2.76
R0 -- S3 R0:edge R0:no-auto-edge
# AutoEdge=false, AdminEdge=true, end device
H3 @0.24,2.32 icon=  proto=none
R0 -- H3 R0:edge R0:no-auto-edge
# AutoEdge=false, AdminEdge=false, bridge
S4 @0,1.42
R0 -- S4 R0:no-auto-edge
# AutoEdge=false, AdminEdge=false, end device
H4 @0.16,0.82 icon=  proto=none
R0 -- H4 R0:no-auto-edge
# Network port, bridge
S5 @0.82,0.16
R0 -- S5 R0:network S5:network
# Network port, end device
H5 @1.42,0 icon=  proto=none
R0 -- H5 R0:network
# AdminEdge=true, bpdu-guard=true, bridge
S6 @2.32,0.24
R0 -- S6 R0:bpdu-guard R0:edge
# AdminEdge=true, bpdu-guard=true, end device
H6 @2.76,0.68 icon=  proto=none
R0 -- H6 R0:bpdu-guard R0:edge

In the topology above, S1, S2, S3, S4, S5, and S6 act as bridges, while H1, H2, H3, H4, H5, and H6 act as end devices:

• S1 and H1 are on a port without a specific configuration: AutoEdge is true, AdminEdge is false,
• S2 and H2 are on a port where AdminEdge is true,
• S3 and H3 are on a port where AutoEdge is false and AdminEdge is true,
• S4 and H4 are on a port where AutoEdge is false.

If you start the simulation and wait about 20 seconds, links to S1, S2, S3, S4, H1, H2, H3, and H4 eventually forward user traffic: none of the flags matter. But what about the two remaining pairs? S5 and H5 connect to a network port. Such a port enables a non-standard feature: bridge assurance. The port transmits BPDUs regardless of its role. If it does not receive BPDUs for 3 consecutive hello periods, it transitions to the discarding state. On the link between R0 and S5, you can see BPDUs traveling in both directions, unlike the other links, where only designated ports send BPDUs. S6 and H6 connect to a port where AdminEdge is true and BPDU guard is enabled. This is another non-standard feature that shuts down a port if it receives a BPDU. In summary, if you expect a port to be an edge port, you should set AdminEdge to true and enable BPDU guard. Otherwise, declare it as a network port.

Why RSTP today? A compelling use case for RSTP today is an out-of-band network for a datacenter, since you can tolerate an outage of a few seconds. The configuration is minimal and you can use cheap switches, like a Cisco 2960X.¹⁴ You need two switches acting as root bridges, and you build several loops to connect OOB switches in each cabinet. This simple design survives one failure on each loop.¹⁵

:protocol rstp
:tx-hold 10
# Root bridges
R1 @0,1 prio=0
R2 @0,2 prio=4096
R1 -- R2 cost=200 R1:network R2:network
R1 -- R2 cost=200 R1:network R2:network
# First loop
C1  @1,0 icon= 
C4  @2,0 icon= 
C7  @3,0 icon= 
C10 @4,0 icon= 
C12 @5,0 icon= 
C13 @5,3 icon= 
C15 @4,3 icon= 
C18 @3,3 icon= 
C21 @2,3 icon= 
C24 @1,3 icon= 
R1  -- C1  R1:network C1:network
C1  -- C4  C1:network C4:network
C4  -- C7  C4:network C7:network
C7  -- C10 C7:network C10:network
C10 -- C12 C10:network C12:network
C12 -- C13 C12:network C13:network
C13 -- C15 C13:network C15:network
C15 -- C18 C15:network C18:network
C18 -- C21 C18:network C21:network
C21 -- C24 C21:network C24:network
C24 -- R2  C24:network R2:network
# Second loop
C2  @1,0.5 icon= 
C5  @2,0.5 icon= 
C8  @3,0.5 icon= 
C11 @4,0.5 icon= 
C14 @4,2.5 icon= 
C17 @3,2.5 icon= 
C20 @2,2.5 icon= 
C23 @1,2.5 icon= 
R1  -- C2  R1:network C2:network
C2  -- C5  C2:network C5:network
C5  -- C8  C5:network C8:network
C8  -- C11 C8:network C11:network
C11 -- C14 C11:network C14:network
C14 -- C17 C14:network C17:network
C17 -- C20 C17:network C20:network
C20 -- C23 C20:network C23:network
C23 -- R2  C23:network R2:network
# Third loop
C3  @1,1 icon= 
C6  @2,1 icon= 
C9  @3,1 icon= 
C16 @3,2 icon= 
C19 @2,2 icon= 
C22 @1,2 icon= 
R1  -- C3  R1:network C3:network
C3  -- C6  C3:network C6:network
C6  -- C9  C6:network C9:network
C9  -- C16 C9:network C16:network
C16 -- C19 C16:network C19:network
C19 -- C22 C19:network C22:network
C22 -- R2  C22:network R2:network

This topology converges in about 6 seconds. Each loop should stay small (around 16 bridges) to reduce the probability of a double failure and to avoid sharing too much bandwidth. The design can evolve a bit without adding too much complexity: one VLAN per loop or one bridge domain per loop.

How large can a network be? The maximum age, whose default value is 20, governs the maximum distance of a bridge from the root. The topology below is too big for BPDUs from R1 to reach beyond S20.¹⁶

:protocol rstp
:tx-hold 10
:max-age 20
R1 @0,0 prio=4096 icon= 
R2 @0,5 prio=4096 icon= 
S1  @1,0
S2  @2,0
S3  @3,0
S4  @4,0
S5  @5,0
S6  @6,0
S7  @6,1
S8  @5,1
S9  @4,1
S10 @3,1
S11 @2,1
S12 @1,1
S13 @1,2
S14 @2,2
S15 @3,2
S16 @4,2
S17 @5,2
S18 @6,2
S19 @6,3
S20 @5,3
S21 @4,3
S22 @3,3
S23 @2,3
S24 @1,3
S25 @1,4
S26 @2,4
S27 @3,4
S28 @4,4
S29 @5,4
S30 @6,4
S31 @6,5
S32 @5,5
S33 @4,5
S34 @3,5
S35 @2,5
S36 @1,5
R1  -- S1
S1  -- S2
S2  -- S3
S3  -- S4
S4  -- S5
S5  -- S6
S6  -- S7
S7  -- S8
S8  -- S9
S9  -- S10
S10 -- S11
S11 -- S12
S12 -- S13
S13 -- S14
S14 -- S15
S15 -- S16
S16 -- S17
S17 -- S18
S18 -- S19
S19 -- S20
S20 -- S21
S21 -- S22
S22 -- S23
S23 -- S24
S24 -- S25
S25 -- S26
S26 -- S27
S27 -- S28
S28 -- S29
S29 -- S30
S30 -- S31
S31 -- S32
S32 -- S33
S33 -- S34
S34 -- S35
S35 -- S36
S36 -- R2
R1  -- R2 cost=200 down

Once the topology settles, part of the network considers R1 the root, while the other votes for R2. At the boundary, S20 tries to start a synchronization with S21 to move its designated port to the forwarding state. The BPDU looks like this:

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x4e, Agreement, Port Role: Designated, Proposal
    Root Identifier: 4096.02:00:00:00:00:00
    Root Path Cost: 400000
    Bridge Identifier: 32768.02:00:00:00:00:15
    Port identifier: 0x8002
    Message Age: 20
    Max Age: 20

S21 rejects it because the message age equals the maximum age. On the other hand, the BPDU S21 sends to S20 looks like this:

Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Rapid Spanning Tree (2)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x7c, Agreement, Forwarding, Learning, Port Role: Designated
    Root Identifier: 4096.02:00:00:00:00:01
    Root Path Cost: 320000
    Bridge Identifier: 32768.02:00:00:00:00:16
    Port identifier: 0x8001
    Message Age: 16
    Max Age: 20

This is not enough to change S20 s root port because S20 has a lower root identifier 4096.02:00:00:00:00:00 vs 4096.02:00:00:00:00:01. Fixing the link between R1 and R2 resolves the issue. The maximum message age any packet carries is now 18, below the configured maximum age. But it only works until another link breaks. A plausible fix is to increase the maximum age to 40.¹⁷

How fast is RSTP? RSTP usually converges in a couple of seconds at startup. It often repairs a tree in less than a second. Even the 38-bridge topology takes less than 10 seconds to converge.¹⁸ Some topologies can take a bit more time to recover when the root bridge becomes unavailable.¹⁹

:protocol rstp
R0 @1,0 prio=0
S1 @1,1 prio=4096
S2 @0,2 prio=8192
S3 @2,2
R0 -- S1
S1 -- S2
S2 -- S3
S3 -- S1

In the topology above, start the simulation, wait for convergence, hit stop, and cut the link between R0 and S1. The topology is already optimal, but RSTP has a hard time converging again. First, S1 loses its root port. It has no more information about R0 and elects itself as the root bridge. It keeps its ports to S2 and S3 as designated ports in the forwarding state. Step once and it sends a BPDU to both S2 and S3 to let them know about the root change. When receiving it, S2 accepts S1 as its root because it does not have a better root on another port. It elects the port to S1 as its root port. The other port stays a designated port. Both ports keep forwarding. When receiving the BPDU from S1, S3 behaves differently: it knows R0 as a better root than S1 through its alternate port to S2. It promotes this port to a root port and demotes the port facing S1 to a designated port, which requires a new agreement. Step once and S3 sends a proposal to S1 with R0 as the root bridge. S1 elects R0 as the root bridge and promotes its port to S3 as a root port. During the same step, S3 also receives a BPDU from S2 stating that S1 is the root bridge. Therefore, S3 has no port left with R0 as the root bridge: it elects S1 as the root bridge and its port to S2 as the root port. Step once and its next BPDU to S1 includes this information: S1 elects itself again as the root bridge. But during the same wave, S1 sends a proposal to S2 with R0 as the root bridge. While S1 and S3 agree that S1 is the root bridge, S2 now believes this is R0! In turn, S2 again convinces S3 that R0 is the root bridge, S3 convinces S1, S1 convinces S2, and S2 convinces S3. This could go on forever, but it does not. The BPDUs saying R0 is root eventually age out when the message age goes past the maximum age. In the example above, at the eleventh second, S2 sends a BPDU to S3 with R0 as root, but S3 drops it because its message age reached the maximum. With some luck, the topology can also converge faster if a port stops transmitting new BPDUs after tripping the transmit hold count, whose default value is 6 per second.

About MSTP MSTP is the VLAN-aware version of RSTP: it runs several instances of RSTP and lets the administrator map each VLAN to a specific instance. For example, you can map VLANs 100 to 200 to a first instance, and 300 to 400 to a second instance. The remaining VLANs map to a special instance named the Internal Spanning Tree (IST). MSTP adds its own complexity, but the gist is that you have several logical topologies acting independently. If you want to dig deeper, have a look at MSTP Tutorial Part I: Inside a Region.

About the interactive examples The interactive examples run MSTPD directly in your browser, compiled to WebAssembly with emscripten. A C API replaces the code talking to the Linux kernel: it manages bridges and ports, exports state as JSON, and drives time deterministically. A JavaScript wrapper makes it more user-friendly:

import   loadMSTPD   from "./dist/mstpd.mjs";
const mstp = await loadMSTPD();
// Create 3 bridges
const a = mstp.createBridge("A",   priority: 4096  );
const b = mstp.createBridge("B",   priority: 8192  );
const c = mstp.createBridge("C");
// Each bridge has two ports
const a1 = a.addPort("a-b",   portno: 1  );
const a2 = a.addPort("a-c",   portno: 2  );
const b1 = b.addPort("b-a",   portno: 1  );
const b2 = b.addPort("b-c",   portno: 2  );
const c1 = c.addPort("c-a",   portno: 1  );
const c2 = c.addPort("c-b",   portno: 2  );
// Build a triangle topology
mstp.link(a1, b1);
mstp.link(a2, c1);
mstp.link(b2, c2);
// Enable all bridges and ports
for (const br of [a, b, c]) br.enable();
for (const p of [a1, a2, b1, b2, c1, c2]) p.enable();
// Execute 40 seconds' worth of wall clock and display the topology
mstp.step(40);
console.log("Topology:", mstp.topology());

Several dozen unit tests explore the features of MSTPD and check that they work correctly in this environment:

$ node --test *.test.mjs
  two bridges: lower priority becomes root (41.657342ms)
  triangle loop: exactly one port blocks and all agree on the root (5.832ms)
  breaking the active link reconverges and restoring recovers (18.730753ms)
[ ]
  tests 40
  pass 40
  fail 0
[ ]
  duration_ms 396.190897

Additional JavaScript code looks for specific <pre> blocks containing a topology definition and turns them into interactive widgets. You can inspect and modify the definition by hitting the edit button. There is also a cool trick to tell whether the topology has converged. After each step, we save a snapshot of the simulation memory, play 50 seconds worth of simulation to check if the topology is stable, and travel back in time by restoring that snapshot. The complete code lives on GitHub. I am happy with the result. It can be difficult to follow everything happening during a single step, but stepping forward and backward helps. I plan to use the same approach in future blog posts about networking features.

Note Michael Lynch reviewed a first draft of this article. He authored Refactoring English, a book to sharpen your writing for blog posts, documentation, commit messages, and tutorials. Any errors are still mine!

---

1. The sprites for Stan and Blobby come from Craftpix, the coffee cups from Yanin.
2. STP was introduced in IEEE 802.1D-1990. It is still present in IEEE 802.1D-1998 but was withdrawn in IEEE 802.1D-2004 in favor of RSTP, introduced in IEEE 802.1w-2001. MSTP was introduced in IEEE 802.1s-2002 and merged into IEEE 802.1Q-2003. Both of them are part of IEEE 802.1Q-2022 along with SPB a protocol I had never heard of until writing this article.
3. From here, I use bridge instead of the more common word switch.
4. The Linux kernel only runs STP. It delegates the other protocols to user space.
5. MSTPD implements the state machine from IEEE 802.1Q-2005, but on Linux it runs RSTP only. Linux 5.18 added support for forwarding multiple spanning tree, but MSTPD does not use it yet. See PR #150 for progress on this front.
6. The priority is a multiple of 4,096: with MSTP, the lower 12 bits of the bridge priority encode the MST instance identifier, leaving only the upper 4 bits for the configured priority.
7. To inspect the BPDUs crossing a link, select it, click the Download packets button, and open the file with Wireshark.
8. A backup port only exists if the bridge has several ports on the same collision domain. This should not happen in a switched network.
9. This is the value of the hello timer. It used to be configurable, but IEEE 802.1Q-2005 pins it to 2. MSTPD does not allow another value.
10. If the peer port does not receive an agreement after the hello timer elapses or the maximum age if the port has just come up it falls back to the timer-based method for compatibility with STP: it transitions to the learning state, waits again for the hello timer to expire, and transitions to the forwarding state.
11. As in many proposals, S3 also sets the agreement bit to 1. The proposal bit says I am the designated port on this link and I want to transition to the forwarding state. The agreement bit says I am already in sync with the rest of my bridge on this root information. Both can be true.
12. If it finds no entry, the bridge duplicates the Ethernet frame on all ports, except the incoming one. The same happens if the destination MAC address is the broadcast one (ff:ff:ff:ff:ff:ff). This behavior bootstraps the learning process.
13. This timer makes RSTP resistant to packet loss.
14. You can get them for less than US$100 through a broker. All the ports run PVST+ by default and automatically fall back to plain RSTP.
15. An alternative would be Ethernet Ring Protection Switching (ERPS) another protocol I had never heard of until researching this article.
16. If you look closely at what happens at t=2s, you can see that R2 is gaining popularity as root: S17 to S36 believe R2 is the root bridge. S16 does not follow because we hit the maximum age. Later, S17 to S20 reverse their position. I ll let you explore the state of the various bridges to understand the root cause.
17. When increasing the maximum age to 40, you also need to increase the forward delay to 21 (:forward-delay 21), as the standard enforces this condition: 2 (Forward Delay 1) Max Age. For this specific topology, you could also increase the maximum age to 37 and forward-delay to 20.
18. The simulation may seem slow, but it does not run in real time. Look at the current timestamp in the upper right corner to know the wall clock, e.g. t=8s. Once the topology stabilizes, the same corner shows the convergence time, e.g. 2s.
19. Khaled Elmeleegy, Alan Cox, and Eugene Ng formalized this phenomenon in On Count-to-Infinity Induced Forwarding Loops in Ethernet Networks and later in Understanding and Mitigating the Effects of Count to Infinity in Ethernet Networks. They propose a fix that did not find its way into a standard.

Activity summary During the month of July, 23 contributors have been paid to work on Debian LTS (links to individual contributor reports are located below). The team released 52 DLAs fixing 2159 CVEs. In July, the Debian Stable Release Managers published the last point release of Debian 12 ( bookworm ), after which the Debian LTS team took full responsibility of Debian 12. This completes the handover from the Security Team, that took place in June. This also marks the second month in a row where the Debian LTS has been focusing on two simultaneous Debian releases. Other than Debian 12, the team is maintaining Debian 11 ( bullseye ), which will reach the end of its Long Term Support on 31 August 2026. After that date, Freexian will continue the security support under the Extended LTS offer. The team published several notable updates:

• jq (DLA 4662-1 and DLA 4661-1) prepared by Andreas Henriksson in collaboration with Jochen Sprickerhof, addressing multiple vulnerabilities.
• Several updates for the different linux supported versions prepared by Ben Hutchings, in collaboration with Emilio Pozuelo Monfort. Other than the regular security advisories: DLA 4664-1, DLA 4665-1, DLA 4671-1, DLA 4688-1, and DLA 4700-1, Ben started preparing packages of 6.12 via bookworm-backports.
• nginx (DLA 4667-1), updated for bookworm by Carlos Henrique Lima Melara, as a follow up of the bullseye update (DLA 4660-1), that was prepared in June.
• grub2/bullseye (DLA 4685-1), prepared by Emilio. Other than addressing several security issues, this DLA was needed for being able to update the shim boot loader.
• samba (DLA 4692-1), uploaded by Markus Koschany, to fix several security flaws in bullseye, including issues that could yield to remote code execution.
• imagemagick (DLA 4680-1 and DLA 4696-1), prepared by Bastien Roucari s, addressing several issues that could lead to denial of service, information disclosure or potentially arbitrary code execution in some scenarios.
• poppler (DLA 4709-1), by Guilhem Moulin, fixing several vulnerabilities.
• nss (DLA-4694-1), by Jochen, fixing flaws that may result in or denial of service or potentially the execution of arbitrary code.

Contributions from outside the LTS Team:

• Guillem Jover prepared the dpkg update, released as DLA-4673-1 by Arnaud.
• Nicholas Guriev released a rlottie security update (DLA 4675-1)
• Bernhard Schmidt prepared the openvpn updates for both bookworm and trixie, released as DLA 4666-1.

The LTS Team has also contributed with updates to the latest Debian releases:

• Bastien also proposed two updates for imagemagick. The first one released as DSA 6383-1, and the second as a trixie point update proposal (#1142554).
• python-httplib2 by Emmanuel Arias, and released by the security team as DSA 6441-1 in August.
• hplip (DSA 6402-1), prepared by Thorsten Alteholz, to address privilege escalation and arbitrary code execution related flaws.
• libnfs trixie update (#1142351), by Thorsten
• patool update for trixie #1141607, by Abhijith PA

Other contributions: Besides the work on security updates, different documentation and tooling changes were needed, especially in the context of the Debian 12 handover. This work was mainly done by Sylvain Beucler.

Individual Debian LTS contributor reports

• Abhijith PA
• Andreas Henriksson
• Andrej Shadura
• Arnaud Rebillout
• Bastien Roucari s
• Ben Hutchings
• Carlos Henrique Lima Melara
• Chris Lamb
• Daniel Leidert
• Emmanuel Arias
• Emilio Pozuelo Monfort
• Guilhem Moulin
• Jochen Sprickerhof
• Lee Garrett
• Lucas Kanashiro
• Lukas M rdian
• Markus Koschany
• Paride Legovini
• Santiago Ruano Rinc n
• Sylvain Beucler
• Thorsten Alteholz
• Tobias Frost
• Utkarsh Gupta

Thanks to our sponsors Sponsors that joined recently are in bold.

• Platinum sponsors:
  • Toshiba Corporation (for 130 months)
  • Civil Infrastructure Platform (CIP) (for 98 months)
  • VyOS Inc (for 63 months)
• Gold sponsors:
  • F. Hoffmann-La Roche AG (for 141 months)
  • CONET Deutschland GmbH (for 124 months)
  • University of Oxford (for 81 months)
  • EDF SA (for 52 months)
  • Dataport A R (for 27 months)
  • CERN (for 25 months)
• Silver sponsors:
  • Domeneshop AS (for 145 months)
  • Nantes M tropole (for 139 months)
  • Akamai - Linode (for 135 months)
  • Univention GmbH (for 131 months)
  • Universit Jean Monnet de St Etienne (for 131 months)
  • Ribbon Communications, Inc. (for 125 months)
  • Exonet B.V. (for 115 months)
  • Leibniz Rechenzentrum (for 109 months)
  • Minist re de l Europe et des Affaires trang res (for 93 months)
  • Dinahosting SL (for 80 months)
  • Upsun Formerly Platform.sh (for 75 months)
  • Moxa Inc. (for 69 months)
  • sipgate GmbH (for 66 months)
  • OVH US LLC (for 64 months)
  • Tilburg University (for 64 months)
  • GSI Helmholtzzentrum f r Schwerionenforschung GmbH (for 56 months)
  • THINline s.r.o. (for 28 months)
  • Copenhagen Airports A/S (for 22 months)
  • Conseil D partemental de l Is re (for 8 months)
  • CEOS GmbH
• Bronze sponsors:
  • Seznam.cz, a.s. (for 146 months)
  • Evolix (for 145 months)
  • Linuxhotel GmbH (for 143 months)
  • Intevation GmbH (for 142 months)
  • WAAYS (for 141 months)
  • Megaspace Internet Services GmbH (for 140 months)
  • Greenbone AG (for 139 months)
  • NUMLOG (for 139 months)
  • WinGo AG (for 138 months)
  • Entr ouvert (for 130 months)
  • Adfinis AG (for 127 months)
  • Plat Home (for 124 months)
  • Laboratoire LEGI - UMR 5519 / CNRS (for 122 months)
  • Tesorion (for 122 months)
  • Bearstech (for 114 months)
  • LiHAS (for 114 months)
  • Catalyst IT Ltd (for 108 months)
  • Demarcq SAS (for 102 months)
  • Universit Grenoble Alpes (for 88 months)
  • TouchWeb SAS (for 80 months)
  • SPiN AG (for 77 months)
  • CoreFiling (for 73 months)
  • Observatoire des Sciences de l Univers de Grenoble (for 65 months)
  • Tem Innovations GmbH (for 59 months)
  • WordFinder.pro (for 59 months)
  • CNRS DT INSU R sif (for 58 months)
  • Soliton Systems K.K. (for 53 months)
  • Alter Way (for 51 months)
  • SOBIS Software GmbH (for 25 months)
  • Tuxera Inc. (for 17 months)
  • OPM-OP AS (for 8 months)
  • LU-CIX Management G.I.E.

Two Debian Days in one week The Debian Project was officially founded by Ian Murdock on August 16, 1993. The Debian community celebrates its birthday, Debian Day, on or around this date every year. This year, I had the chance to attend two of them: one in Jo o Pessoa, Para ba, and another in Bras lia, the capital of Brazil.

Jo o Pessoa In Jo o Pessoa, we had a two-day event. The first day was dedicated entirely to workshops, and I ran a packaging workshop for newcomers. It was the first time I had been responsible for a workshop, and it was a great experience. We didn't have a lot of time, so I decided to start with a 30-minute talk explaining a few things about Debian. For example, I made this image to explain the packaging workflow: This image was based on The Debian Administrator's Handbook, and I think the participants really enjoyed learning about this workflow. When I showed the slide with this image, it was the moment when I received the most questions. After the talk, I explained my way of working and what they were going to do. The hardest part was setting up the environment, since my approach uses sbuild + gbp. They were running different Debian releases and, because of my inexperience with workshops, I had some of them configure sbuild with unshare, even though it is only available in stable through backports. Some of them even managed to learn how to use backports, while others decided to start again using the "old" way. One thing that helped a lot was the Debian Brasil Wiki. It has all the instructions for configuring sbuild in Portuguese, along with great examples. The Brazilian wiki is an opinionated version of the Debian Wiki. We generally prefer to use it for the convenience of having the exact workflow we follow, as well as an up-to-date Portuguese version of our process. If you want to learn more about the Brazilian community, you can find more details in the schedules from previous DebConfs. We almost always had a talk about the community and its activities. In the end, everyone successfully set up their development environment, and all six participants made their first contribution to Debian. If you take a look at my upload tracking page, you will see that every upload made on August 15, 2026 was a sponsored upload from this event. One of them appear twice in the list because I sponsored the upload and also made some other changes. I also asked all of them to put this in their changelog:

* My first contribution!

The idea was to make it clear to other people that they were only working on small Lintian issues as a way of learning and understanding the process. By the way, I made a UDD query to find packages with the following Lintian tag: redundant-rules-requires-root-no-field. To fix this issue, they only had to remove one line from the debian/control file. It is obvious that these uploads are not particularly useful. I call them "motivational uploads" because my goal is to help newcomers understand the process and immediately give them the reward of having made a contribution to Debian. I'll try to keep in touch with them. My plan is to hold another session, this time remotetly, to help them continue contributing to Debian. In fact, I already have another package prepared by one of them waiting for my review. The second day was a full-day event featuring a bunch of talks from the local community. I gave a talk explaining the new members process. I was the only Debian Developer at the event, and I think having a DD there made a real difference. Being there to answer questions, and simply being present, makes Debian feel more tangible and accessible to people. A big shout-out to Rafael Rocha, who put in a lot of work to make this event happen, with the help of many volunteers who contributed along the way.

Bras lia One thing I really like about Debian Days is that each place has its own way of doing things. In Jo o Pessoa, we had a MiniDebConf-like event, while in Bras lia, we had something smaller but still very valuable. We decided to keep things simple: talk to a few students at the University of Bras lia (UnB) and then go somewhere to eat and have a few drinks.

A bit of history For those who don't know, the DebConf 19 was held in Curitiba, Brazil. After the event, Arthur Diniz got really excited about Debian and decided to go back to his University, UnB, to share his experience and encourage more people to contribute to Debian. I attended one of his talks, thanks to Joenio Costa, who invited Arthur to give the talk. Joenio was also my professor at the time and a Debian contributor. I really liked what Arthur had to say about free software, and he did a great job of presenting the Debian community as a friendly and welcoming place. So I decided to attend local meetings of the Debian Bras lia community, which had been inactive for a long time. Lucas Kanashiro was the Debian Developer who answered our questions and, as I mentioned earlier, simply being there made Debian feel more tangible. Everything stopped when the pandemic began. Then, towards the end of 2020, I saw a message in the Debian Bras lia channel saying that the meetings were back, this time remotely. I was hesitant to join because, back in 2019, I hadn't managed to make a packaging contribution, even with their help. I had eventually given up on the process. So this time, I decided to join the meeting with something already prepared for review. I watched all of Eriberto's packaging videos, picked a random package, and joined the meeting. I remember Kanashiro being excited that someone had just shown up with something ready for review. At the time, it was only the second meeting since Debian Bras lia had come back online, and none of the newcomers had started working on contributions yet. During the same meeting, he also convinced us, the newcomers, to give a talk about Debian just three days later. The MiniDebConf Online Brazil 2020 was happening on Sunday, and the meeting was on the Thursday before it. Since he has great convincing skills, I went along with the idea and prepared the talk with Francisco Ferreira. That was the rebirth of the Debian Bras lia community. Since then, we have maintained a close connection with the University of Bras lia, and today, at least seven Debian Developers are from UnB, whether as former students or former professors. The reason I told this story is that, even though the Debian Day we held in Bras lia was smaller, it is part of something that has been working for us for several years: staying close to an University. We've managed to attract and retain many people who share the same values and interests. I've hope you all had a great Debian Day. If you're reading this and aren't part of the Debian community but would like to join, get in touch!

• Proposal A(1) - Action: ban all AI-assisted contributions via Social Contract amendment, except from upstreams (so not rolling back the Linux kernel and other software to "pure", pre-AI state). Claims that copyright/licensing status is unclear, quality is bad, community is being destroyed, web resources see extra load and that training consumes "staggering" resources. Needs 2/3rd majority to pass. - IMHO worst and most inconsistent. If copyright and licensing of AI products is unclear, then be consistent - ban ALL software with AI contributions, fork Linux kernel and other software from pre-AI versions, reject all security fixes of issues found with AI. Quality section lists problems that have not existed in the real world since at least a year of rapid AI coding development. Community section assumes that now all Debian contributions will be drive-by AI slop and no one will learn anything anymore. Ethics section mixes up effects of badly configured systems (AI web load is no different from load from a badly configured Perl script) with claimed "resource" usage without any context, taking on trust project ambitions of startups and assuming exponential growth. And then concludes that delivering less is in the interest of our users somehow.
• Proposal B(2) - Action: allow AI-assisted contributions, with conditions of: legality, accountability, disclosure, no uncoordinated bulk actions, privacy. Concerns on quality and legal status as well as environmental impact and scraper load are noted, but not really addressed beyond labelling them as concerns. - IMHO it is an ok starting position as it establishes that each contributing person must still be fully responsible for their contribution (both legally and technically) and for that has to also understand (and review) what they submit. Disclosure lets others know to watch out for other classes of problems when code was changed with AI assistance. Prior discussion for bulk changes just says that the (already established) practice should not be neglected just because now large changes are easier to do. And the privacy part warns against accidentally sending private or confidential data (like a not yet published security bug) to a public service where it could become public. Personally I would have liked a stronger statement to encourage use of environmentally responsible AI services and local AI tools. Possibly a preference for open-weight models with a clear path forward to preferring truly free AI models, when such a category of products could be clearly delineated and established.
• Proposal C(3) - Action: reject AI-assisted contributions at Code of Conduct level. Claims all the world's evils come from LLMs and that "Ethical and safe use of this technology is almost impossible". Goes as far as banning any use of LLMs even in Debian mailing list emails and Debian Planet blog posts - if you do, it's a CoC violation and may result in exclusion from the project. Additionally mandates the disclosure of the usage ... presumably to ban you more efficiently for it. - IMHO truly a dictatorial nightmare option. Zero actual reasoning or basis for such a decision. Zero sources. Nothing claimed in this option's rationale is even close to reality and nothing claimed there is in any way related to the actual technology being discussed. Like, an "LLM" does not automagically commit "fraud" when you use it, like this proposal claims, as if that was a well-known fact. LLMs are not all "owned by horrible people and companies". Even if some include a (prominent Debian user, long-time supporter and sponsor) Google into "horrible companies" (which is what this proposal implies!), there are plenty of LLMs owned by all kinds of companies all over the world and there are plenty of open-weight LLMs that are not really owned by anyone. Most invasive and dishonest option on the ballot.
• Proposal D(4) - Action: allow AI-assisted contributions, with conditions of: legality, accountability, disclosure, privacy. IMHO same as B, just shorter. Adds a "we don't recommend" towards others developing software with AI assistance. Seems pretty weird to add that and then immediately accept Debian contributors doing so. Assumes that the bulk change bit of B is implied as AI is just tooling, so bulk changes should be pre-discussed just like today - so no change and thus no point in mentioning that. Fair. D is a bit more explicit on expected technical details - like that the "person" submitting the change is supposed to sign it, not AI. Notable is the complete absence of resource usage or the environment from concerns. IMHO it would be better to have that and also recommendations on how to avoid causing environmental damage when using AI.
• Proposal E(5) - Action: no action as such - AI-assisted contributions must follow the same rules as all other contributions and those rules are sufficient. IMHO despite its length this is a very well-worded position statement that describes how and why AI-assisted contributions already work perfectly fine in the Debian context when all the same rules that apply to all contributions are also consistently applied to AI-assisted contributions. It describes how the same legality, accountability, no bulk change and privacy requirements are already in place and still apply and how AI-assisted contributions can and must still satisfy them. I could add again that some guidance would be nice here for both legal and environmental decisions when using AI, but in this case it does not really belong in this proposal itself. We as Debian do not have a document that requires that our non-AI-assisted contributions be made with only sustainably sourced electricity, for example. So why should AI be special one way or another? IMHO Debian should have a datacenter sustainability policy, regardless of the AI discussion.
• Proposal F(6) - Action: discourage AI, but allow it based on existing processes (similar idea to E). Dances a bit around the question of disclosure of AI use (as a courtesy) and accepting that some people may still ban all contributions where any AI was involved in any way. Which in turn discourages disclosure to avoid pointless rejection of valuable contributions (like security patches). IMHO this option is ok, but so watered down that it is bound to bring up further discussions and conflicts on details.
• Proposal G(7) - Action: ban non-humans from directly contributing to Debian. IMHO - another bizarre and self-contradictory option. It bans all Debian interactions with AI assistance, including email messages to Debian mailing lists and (supposedly) blog posts on Planet Debian. It "reminds" people who "use such tools assistively" of the DFSG and Social Contract - isn't that a threat of a ban and expulsion similar to C? The proposal does take pains to delineate where a contribution comes from AI as output (bad) vs when you are assisted by AI in the process of exploring, researching or maybe even reviewing the code, but you actually type all the code yourself and use the AI just as a taskmaster with a whip (good). And just like A or C it completely ignores how this inherently evil and unstable AI-generated code becomes perfectly fine and good as soon as someone develops that outside of the Debian project. Even if the same person then packages it for Debian the next day. It is hypocritical, unsustainable and ignores the needs of our users. Just like C it also bans someone writing an email or bug report in their native language and using a modern translation tool or service (that uses LLMs nowadays for better grammatical clarity) to translate that to English before sending it to a Debian mailing list or BTS. Heavy-handed and invasive. And the only reasoning provided for this is some unnamed "concerns" of "extra work" being borne by "other people"? Kind of does not feel right to bear such draconian restrictions for some unspecified concerns.
• Proposal H(8) - Action: condemn usage, but not actually ban anything. And then it goes on to claim (without any evidence or elaboration) that LLM usage accelerates the destruction of "planet earth" (sic). IMHO this proposal is at the same time the loudest ("The planet is burning") and also the one that demands the least action. It dances a really twisty line between raising "significant" concerns in all areas and even claiming that use of LLMs destroys the planet, flies by explicit condemnation of LLM usage and then suddenly collapses with not condemning LLM users and swinging to lamentations that it is actually impossible to impose policies on LLM usage or even detect when an LLM was used (which kind of directly contradicts bad quality claims from A, C and G) and lands on "encouraging" contributors not to use LLMs (where practical) and otherwise do nothing else. It's like this is a 5th draft that started off with the rationale and total ban like in C, but then got defanged so far that its action side no longer matches the rationale stated.

• Proposal E(5) - solid hack of integrating AI into already existing Debian rules and conventions
• Proposal B(2) - explicit and detailed
• Proposal D(4) - lower because of discouragement to others on what we agreed to do ourselves
• Proposal F(6) - I am not a fan of dancing around with disclosures
• Further discussion(9) - I do not want any option below this to succeed as they would do more harm than good
• Proposal H(8) - loud, but not doing anything actually
• Proposal A(1) - at least this one does not set rules for emails
• Proposal G(7) - at least this one allows an AI overseer to tell you what to write with your own fingers
• Proposal C(3) - the most draconic and invasive one that explicitly wants to kick people out of the project

• information on which AI services have Terms and Conditions that make them problematic for free software development, legally speaking
• information on which AI services do (or do not) achieve a sufficient level of sustainability to be worth recommending (and then do the same for other data centers we already use)
• information on which local AI models were trained in sustainable ways
• base-level prompts to set technical expectations on various types of contributions, like bug reports or patches to packaging or translations
• default configuration for AI-assisted code reviews on Salsa that projects could enable and supplement with their own instructions on top

• encourage them to improve sustainability (where needed)
• investigate and fix problems causing excessive scraping load on systems
• provide AI resources for Debian usage, for example in CI infrastructure or to provide equal development support opportunities for Debian developers who cannot afford paid AI services
• improve coding outputs of their models in the Debian context if/when systematic deficiencies in the output are found by us

My experience at DebConf 2026 in Santa F Last month, I attended DebConf 2026 in Santa F , which was my 5th DebConf. As always, it was an amazing experience, and I met a lot of great people there. For those unfamiliar with the event, it takes place over the course of two weeks. The first week is called DebCamp and is geared more towards hacking and organizing the event itself, while also offering a great opportunity to discuss ideas with others. The second week is the DebConf. We still have the hacklabs, but the talks and workshops are the main focus.

My Activities during DebCamp My main activity was working on the python-click transition that I started in May. There were only a few packages left, and with the help of Guilherme Puida, we managed to work through all the remaining bugs. I plan to talk in details about this transition in another blog post, where I will focus on the tools I used and my experience with mass rebuilds and mass bug filing. I also helped with de Golang Sprint. I worked on a few packages and experimented with the dak API to generate a list of packages that needed manual action. There was a lot of manual, repetitive work and false positives, so I eventually moved on to some other, more fun stuff. I also learned a few thinks about kernel live patching while talking to David Tadokoro. I had to work on the Ubuntu Kernel package recently as part of my job, so we exchanged some ideas, and the conversation was really helpful. He also taught me two commands that I wasn't familiar with, since I'm a newbie in kernel development. Here are the commands:

$ b4 am https://lore.kernel.org/lkml/20240730071904.1047-1-sergiosacj@riseup.net/
$ b4 diff *mbox

By the way, this is the first and only patch I have submitted to the Linux Kernel. I worked on it during DebConf 2024, when I attended the workshop Helen Koike runs to help newcomers submit their first patch to the Linux Kernel. Another great interaction was with Marcos Talau. He showed me his remote access setup, which he is using to help students make contributions to Debian without the struggle of setting up the development environment. Another cool thing is that Puida showed me the command:

$ gbp clone vcs-git:typer

After that, I decided to read the gbp manpage because these little details really improve the overall experience. I also had many other amazing interactions. I just decided to write down the ones that I felt made the most sense for this kind of "blog report" post.

My Activities during DebConf I gave a talk about dh-make-vim, a tool I have been working on sporadically. An interesting detail is that one of the video team volunteers for the talk, Piotr, spoke to me about his tool, pypi2deb, which is similar but aimed at the Python ecosystem. There are many tools of this kind in Debian, and they are all interesting pieces of software. I plan to write more about them in the future. I attended several talks and participated in a few BoF sessions, and they were all great. But something that really stood out to me was the workshop on the Debian Installer, led by Alper Nebi Yasak. I didn't know anything about the Debian Installer, and I liked the way he approached the subject and showed the specific details. I'll take some time to read the Debian Installer internals documentation. I was not familiar with udebs or with the fact that the Debian Installer uses debconf under the hood.

Wrap up It was an amazing event. Unfortunatly, a lot of people I know were not able to attend for different reasons, and they were missed. There were many other things that I enjoyed during this trip. Here are a few more highlights:

• World Cup matches
• A day trip around Santa F
• The Cheese & Wine party
• Empanadas!!

Changes in version 0.2.5 (2026-08-19)

• Explicitly include header "type_traits.h" to appease clang++-23
• Standard maintenance updating continuous integration, adding minor helper script, and updating README.md

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. If you like this or other open-source work I do, you can now sponsor me at GitHub.

Also in this series:

• The Four Horsemen of the LLM Apocalypse
• A more nuanced view of LLMs

How people use models People using LLMs in their workflow have radically changed how programming works, even for people who claim to avoid vibe-coding. And I'm sorry to single out one poor maintainer here: it's not you, Brian, you're just one example among many. But this is typical use of those models nowadays:

Once it s done, I ll use /code-review and let Claude spawn sub-agents to do a full review of the new code. This usually finds some problems, even problems that the main Claude instance didn t find during its validation. I usually keep running /code-review again and again after finding and fixing issues, until there aren t any left.

Think about what that means for a minute. This is automation built to fire up dozens of agents crunching at a problem for minutes if not hours of GPU compute time, in parallel. This is essentially a couple of shelves in a datacenter rack, totally maxed out on power and cooling, abstracted behind a cute little /code-review command. The author, here, is rightly concerned that "Anthropic could pull the rug out and require API pricing", which is perhaps a code word for "charging something closer to actual costs". Brian also pays lip service to environmental and societal costs but those are largely abstracted away, so let's keep that conversation aside here as well, as we have discussed it before anyways. But clearly, this way of working has an (externalized) cost, to say the least.

Paying for non-free tools For decades my work has been focused on free and open source software. I've long stopped using proprietary operating systems like Windows or Mac, and even before that switch, I was mostly using free software on those platforms, partly out of principle, but also because I was too poor. So the tools of my trade are free, and I build free tools with them. It feels like we're going backwards: when I was in school, a millennia ago, my classmates didn't have access to a compiler and were wondering how they would scrape the money to buy a compiler like Borland's or Microsoft's. I had a compiler built into my operating system (FreeBSD at the time), so that wasn't a problem for me. For them, it was a significant expense, but at least those expenses (or more shady sourcing of programs) were a one-shot deal. Fast forward 30 years, and software is rented: you pay monthly for Adobe's Photoshop and Microsoft's office suite just like you pay for Netflix, Disney+ or Spotify². And now you need to add dozens (if not hundreds of dollars) of monthly credits to access LLMs on top of that. So, now we have to pay to get anything done? This is peak enshitification of our job: first they steal our work to train their models, and then they sell it back to us at a profit.

Attacking the engineers AI is coming for our jobs, as engineers, if not everyone, according to the narrative. For a while now, our job market has deteriorated: less jobs, for less pay. Lots of skilled engineers looking for work and finding crap jobs then still looking while working. This is not by accident.³ We engineers have a lot of power, it is not organized, but that's just a couple of unions away (easy!). Tech overlords know this, so they are attacking our profession, directly, by forcing us to train and use models that they can control. Even in environments where programmers are not forced to use LLMs, the mere pressure of other people's LLM-generated work is huge. One can be forced to review LLM outputs, or just peer pressured you into producing more. We're now supposed to accelerate delivery, because models can presumably do things so much better and faster. With supply chain security becoming such a large vector that we now have worms crawling around developers accounts on NPM, increasing the delivery cadence seems like a really bad idea.⁴ The LLM hype is part of the larger wave of cyberwar against workers, against water, against the Earth, against all the people. This is not a matter of individually "adapting to the reality" or personal choice, but a political, social, hard problem we need to address collectively.

---

1. I again prefer the term LLM to "AI" because models do not possess intelligence. I did use it in the title because click baiting is apparently important, but I stopped short of calling this one "Rage Against the Machines" because that would be the title of every blog post I have ever made.
2. Yes, I know that Visual Studio is kind of free now, but I wouldn't be surprised if they turn that into a rental as well, because why not.
3. Beyond sabotaging the job market, Sam Altman event wants to sell "intelligence as a utility" something that is just a really bad idea but especially shows how megalomaniac those people are.
4. This brings back memories of another era, walking us back decades in terms of computer security.

            Loading Linux 6.12.100+deb13-amd64 ...
            Loading initial ramdisk ...

            Loading Linux 6.12.100+deb13-amd64  
            Loading initial ramdisk ...
            
            	EFI stub: Loaded initrd from LINUX_EFI_INITRD_MEDIA_GUID d
            	evice path
            		EFI stub: Measured initrd data into PCR 9

• Confirmed that I could still boot the machine with the old kernel 6.12.88+deb13-amd64 (During boot select Advanced options from the grub menu followed by the kernel image wanted)
  • Yes the system starts happily with the previous kernel
• Checked that /boot had enough space
  • Yes plenty of space
• Is anyone else reporting this problem?
  • Nothing jumps out on Debian s bug tracker
  • Actually not mush referenced for my search EFI stub: Measured initrd data into PCR 9 apart other than the usual rantings to turn off secure boot (on this server that currently isn t turned on bad me)

• wget each kernel package then install (dpkg -i) followed by an update-grub, checking that there was sufficient space on disks especially my small /boot partition)
• I started with image 6.12.95+deb13 and this worked
• 6.12.96+deb13 yielded the same lock up on boot as 6.12.100+deb13

Up until now I have been walking to my garage where the server is located and standing in front of a rack
with a monitor and keyboard plugged into the machine. However this machine supports IPMI so I spent a little time getting that up and running so that I can continue from the relative comfort of my desk (with lights, a chair and not needing to hold the keyboard with one hand) Great I can now grab screen shots from the confort of my desk (unfortunatly they are only screen shots not text files, but at least we can seen the early stage of boot, Post, grub menu and then initramfs before system log happens) (5) Collating information for the initial bug report Sledge had mentioned my problem in irc/#debain-kernal where iam_tj suggested that we try appending
debug earlycon=efifb to the kernal command line. This yielded 15 seconds worth of messages before the system locked up the last few messages being (vmlinuz-6.12.96+deb13-amd64):

[ 14.663477] RCU Tasks: Setting shift to 5 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=20.
[ 14.750474] RCU Tasks Rude: Setting shift to 5 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=20.
[ 14.838024] RCU Tasks Trace: Setting shift to 5 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=20.
[ 14.929752] NR_IRQS: 524544, nr_irqs: 584, preallocated irqs: 16
[ 15.016814] rcu: srcu_init: Setting srcu_struct sizes based on contention.
[ 15.104011] Console: colour dummy device 80 25
[ 15.191236] printk: legacy console [tty0] enabled
[ 15.278249] printk: legacy bootconsole [efifb0] disabled Booting the working kernel with the same kernel options yields the SAME messages with slightly differing times, but then continues to login prompt:

 [   14.697466] RCU Tasks: Setting shift to 5 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=20.
 [   14.784936] RCU Tasks Rude: Setting shift to 5 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=20.
 [   14.872067] RCU Tasks Trace: Setting shift to 5 and lim to 1 rcu_task_cb_adjust=1 rcu_task_cpu_ids=20.
 [   14.964000] NR_IRQS: 524544, nr_irqs: 584, preallocated irqs: 16
 [   15.051482] rcu: srcu_init: Setting srcu_struct sizes based on contention.
 [   15.226079] printk: legacy console [tty0] enabled
 [   15.313751] printk: legacy bootconsole [efifb0] disabled
 [   15.400831] ACPI: Core revision 20240827
 [   15.401415] clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635855245 ns
 [   15.401464] APIC: Switch to symmetric I/O mode setup
 
... and so on

[ 34.285342] BUG: kernel NULL pointer dereference, address: 0000000000000000

[6.12.96+deb13-amd64 debug earlycon=efifb keep_bootcon.tar.gz (application/gzip, attachment)]

[dmidecode.txt (text/plain, attachment)]

[lscpu.txt (text/plain, attachment)]

[lspci.txt (text/plain, attachment)]

git clone --single-branch -b linux-6.12.y https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
cd linux-stable
git checkout v6.12.95
cp /boot/config-$(uname -r) .config
yes ''   make localmodconfig
make savedefconfig
mv defconfig arch/x86/configs/my_def
test 6.12.96 to ensure this is "bad"
git checkout v6.12.96
make my_defconfig
make -j $(nproc) bindeb-pkg
  install the resulting .deb package and confirm it fails to boot and triggers the NULL pointer dereference.

git bisect start
git bisect good v6.12.95
git bisect bad v6.12.96

git checkout 977855894bca4b87afa50d21e3f3e85a5a0e901f
build and install .
fails
git bisect bad

git checkout 977855894bca4b87afa50d21e3f3e85a5a0e901f~1 ## ~1 is the commit beforehand
build and install .
fails
git bisect good The entire test tree can shown with git bisect log and this was submitted as an email to the bug report, we have found our smoking gun :-) Finally I would like to thank Carnil, Iam_tj for their time patience and fantastic support in guiding me through finding this regression. Right now kernel bugs are coming in thick and fast with a lot of AI assisted bug hunting, the increased numbers of bugs mean that the kernel team are especially busy. Hopefully our paths will cross and I ll be able to buy you some beers (or whatever) soon. thank you. Sledge also deserves thanks for putting up with me and pointing me in the right direction (as ever). Lucky for me that he lives nearby so I can provide beers on a regular basis :-)

For human developers, using coding LLMs magnifies their difference in skill levels.

• Packaging upstream software for Debian (by far the largest task)
• Writing Debian-specific code (eg, apt or the Debian installer)
• Maintaining Debian infrastructure (build systems, for instance)
• Writing documentation and translations

• Proposal A: seeks to amend the social contract, which I am opposed to for reasons already laid out above. It names some real concerns about AI that I agree with, but implies that all LLM uses and models are guilty of the problems, which is not the case with all of the claims. It also sets us behind the curve on security and stability by forbidding the use or assistance of those tools, even if run by others. It requires us to ignore reports of actual security bugs, or correct fixes, if those reports were generated with the assistance of an LLM, which I find to be absolutely untenable.
• Proposal B: This is the AI with accountability approach. It notes the real concerns with LLMs without painting with an overbroad brush. It strikes me as level-headed and sensible.
• Proposal C: It paints with an over-broad brush and makes some non-binding requests. Then it winds up largely like proposal B, though while it is worded more strongly, has fewer binding requirements (for instance, it lacks proposal B s prohibition on transmitting sensitive information to untrusted providers)
• Proposal D: Seems broadly similar to proposal B, an AI with accountability approach. I m not really clear why we need both.
• Proposal E: Largely the status quo. It is like proposals B and D in that it says humans are accountable for their contributions. It encourages disclosure of LLM use, but does not mandate it. Like proposal B, it prohibits disclosing sensitive information to third-party AI services. Note that both proposals B and D have an appropriate nuance: a local model is fine, a third-party one is not.
• Proposal F: This seems really similar to proposal E. I m not sure why we have these two.
• Proposal G: Disallows the output of generative AI as direct contributions to Debian. This is something of a weakened proposal A; it doesn t seek to amend the social contract, nor does it ban all use; it simply bans the use as a direct contribution.
• Proposal H: Ban due to climate impacts. How is this even an argument is disrespectful to reasoned conversation. I have already noted that LLMs can be and are used in ways that are not climate-harming. It explicitly contains no binding requirements at all, and is effectively a rant. While I agree with the sentiment that climate change is an urgent problem, and that some LLMs are exacerbating it, I disagree with that all LLM usage does so and therefore disagree with the conclusion.

• [1] https://etbe.coker.com.au/2025/11/09/amd-video-driver-issues/

2026-08-09T23:03:06.004792+10:00 xev kernel: amdgpu 0000:02:00.0: GPU fault detected: 147 0x00024802
2026-08-09T23:03:06.004792+10:00 xev kernel: amdgpu 0000:02:00.0: Process kscreenlocker_g pid 42037 thread kscreenloc:cs0 pid 42044
2026-08-09T23:03:06.004793+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_ADDR 0x00000800
2026-08-09T23:03:06.004794+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_STATUS 0x0F048002
2026-08-09T23:03:06.004795+10:00 xev kernel: amdgpu 0000:02:00.0: VM fault (0x02, vmid 7, pasid 130) at page 2048, write from 'TC0' (0x54433000) (72)
2026-08-09T23:03:06.008762+10:00 xev kernel: amdgpu 0000:02:00.0: GPU fault detected: 147 0x00004802
2026-08-09T23:03:06.008768+10:00 xev kernel: amdgpu 0000:02:00.0: Process kscreenlocker_g pid 42037 thread kscreenloc:cs0 pid 42044

2026-08-04T01:13:37.505839+10:00 xev kernel: ------------[ cut here ]------------ 
2026-08-04T01:13:37.505859+10:00 xev kernel: amdgpu 0000:02:00.0: [drm] drm_WARN_ON_ONCE(cur_vblank != vblank->last) 
2026-08-04T01:13:37.505862+10:00 xev kernel: WARNING: CPU: 6 PID: 210534 at drivers/gpu/drm/drm_vblank.c:362 drm_update_vblank_count+0x2f1/0x3c0 [drm] 
2026-08-04T01:13:37.505866+10:00 xev kernel: snd_intel_dspcfg wmi_bmof rc_core snd_intel_sdw_acpi drm_ttm_helper uas realtek snd_usbmidi_lib snd_hda_codec ttm mdio_devres snd_hda_core snd_seq_midi drm_kms_helper usb_storage mc snd_hwdep libphy snd_seq_midi_event intel_uncore snd_pcm_oss i2c_algo_bit serio_raw snd_rawmidi pcspkr snd_mixer_oss i2c_i801 video snd_seq snd_pcm i2c_smbus lpc_ich snd_seq_device mei_me e1000e snd_timer mei snd tpm_infineon soundcore joydev bnx2 wmi button nfsd auth_rpcgss nfs_acl lockd grace sunrpc coretemp br_netfilter bridge stp llc sg ghash_clmulni_intel loop msr i2c_dev drm efi_pstore configfs nfnetlink ip_tables x_tables autofs4 btrfs blake2b_generic dm_crypt dm_mod raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx libcrc32c xor raid6_pq raid1 raid0 md_mod ext4 crc16 mbcache jbd2 crc32c_generic virtio_blk evdev hid_generic usbhid hid sd_mod xhci_pci xhci_hcd ahci ehci_pci ehci_hcd libahci crc32c_intel libata usbcore aesni_intel nvme psmouse scsi_mod gf128mul crypto_simd nvme_core cryptd 
2026-08-04T01:13:37.505879+10:00 xev kernel: nvme_auth scsi_common usb_common efivarfs 
2026-08-04T01:13:37.505880+10:00 xev kernel: CPU: 6 UID: 1008 PID: 210534 Comm: sshd-session Tainted: G D 6.12.88+deb13-amd64 #1 Debian 6.12.88-1 
2026-08-04T01:13:37.505881+10:00 xev kernel: Tainted: [D]=DIE 
2026-08-04T01:13:37.505883+10:00 xev kernel: Hardware name: Hewlett-Packard HP Z640 Workstation/212A, BIOS M60 v02.61 03/23/2023 
2026-08-04T01:13:37.505884+10:00 xev kernel: RIP: 0010:drm_update_vblank_count+0x2f1/0x3c0 [drm] 
2026-08-04T01:13:37.505885+10:00 xev kernel: Code: 48 8b 5f 50 48 85 db 75 03 48 8b 1f e8 68 eb 2b cf 48 c7 c1 70 3e cb c0 48 89 da 48 c7 c7 f9 6f cb c0 48 89 c6 e8 af d7 a6 ce <0f> 0b e9 4b fe ff ff 48 8b 4c 24 18 e9 31 fe ff ff 31 f6 48 85 db 
2026-08-04T01:13:37.505887+10:00 xev kernel: RSP: 0000:ffffd3cc8681fca0 EFLAGS: 00010082 
2026-08-04T01:13:37.505888+10:00 xev kernel: RAX: 0000000000000000 RBX: ffff8c6b42b13710 RCX: 0000000000000027 
2026-08-04T01:13:37.505889+10:00 xev kernel: RDX: ffff8c89ef521788 RSI: 0000000000000001 RDI: ffff8c89ef521780 
2026-08-04T01:13:37.505890+10:00 xev kernel: RBP: 0000000000000000 R08: 0000000000000000 R09: ffffd3cc8681fb20 
2026-08-04T01:13:37.505891+10:00 xev kernel: R10: ffff8c8a6fef3628 R11: 0000000000000003 R12: 0000000000000000 
2026-08-04T01:13:37.505892+10:00 xev kernel: R13: ffff8c6c07853828 R14: 0000000000000003 R15: 0000000000000000 
2026-08-04T01:13:37.505893+10:00 xev kernel: FS: 00007ffaf2fd5880(0000) GS:ffff8c89ef500000(0000) knlGS:0000000000000000 
2026-08-04T01:13:37.505895+10:00 xev kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 
2026-08-04T01:13:37.505896+10:00 xev kernel: CR2: 00007fb1718c8000 CR3: 000000074521a004 CR4: 00000000003706f0 
2026-08-04T01:13:37.505897+10:00 xev kernel: Call Trace: 
2026-08-04T01:13:37.505898+10:00 xev kernel:  
2026-08-04T01:13:37.505899+10:00 xev kernel: drm_crtc_accurate_vblank_count+0x41/0xc0 [drm] 
2026-08-04T01:13:37.505900+10:00 xev kernel: dm_pflip_high_irq+0x155/0x330 [amdgpu] 
2026-08-04T01:13:37.505901+10:00 xev kernel: amdgpu_dm_irq_handler+0x85/0x1f0 [amdgpu] 
2026-08-04T01:13:37.505902+10:00 xev kernel: amdgpu_irq_dispatch+0xd2/0x230 [amdgpu] 
2026-08-04T01:13:37.505903+10:00 xev kernel: amdgpu_ih_process+0x84/0x100 [amdgpu] 
2026-08-04T01:13:37.505904+10:00 xev kernel: amdgpu_irq_handler+0x23/0x60 [amdgpu] 
2026-08-04T01:13:37.505905+10:00 xev kernel: __handle_irq_event_percpu+0x4a/0x190
2026-08-04T01:13:37.505907+10:00 xev kernel: handle_irq_event+0x38/0x80 
2026-08-04T01:13:37.505908+10:00 xev kernel: handle_edge_irq+0x8b/0x230 
2026-08-04T01:13:37.505909+10:00 xev kernel: __common_interrupt+0x45/0xe0 
2026-08-04T01:13:37.505910+10:00 xev kernel: common_interrupt+0x42/0xa0 
2026-08-04T01:13:37.505911+10:00 xev kernel: asm_common_interrupt+0x26/0x40 
2026-08-04T01:13:37.505912+10:00 xev kernel: RIP: 0033:0x7ffaf3c5fd7b 
2026-08-04T01:13:37.505913+10:00 xev kernel: Code: 70 c7 00 66 0f 6e f8 c1 ef 02 66 0f 70 f7 e0 83 c7 01 66 0f ef ff 66 0f fa f2 0f 1f 44 00 00 f3 0f 7e 01 66 0f 6f ce 83 c6 01 <48> 83 e9 08 f2 0f 70 c0 1b 66 0f 6f e0 66 0f 6f e8 66 41 0f f9 c0 
2026-08-04T01:13:37.505915+10:00 xev kernel: RSP: 002b:00007fff86a5e0e0 EFLAGS: 00000202 
2026-08-04T01:13:37.505916+10:00 xev kernel: RAX: 0000000000008000 RBX: 0000562614a04050 RCX: 0000562614982ed8 
2026-08-04T01:13:37.505946+10:00 xev kernel: RDX: 0000000000007fe2 RSI: 0000000000000fad RDI: 0000000000002000 
2026-08-04T01:13:37.505948+10:00 xev kernel: RBP: 0000000000000000 R08: 000056261498ac40 R09: 0000000000008000 
2026-08-04T01:13:37.505949+10:00 xev kernel: R10: 0000000000000066 R11: 0000000000007fe1 R12: 0000000000007efa
2026-08-04T01:13:37.505950+10:00 xev kernel: R13: 0000000000008000 R14: 0000000000008000 R15: 000000000000ffe0 
2026-08-04T01:13:37.505951+10:00 xev kernel:  
2026-08-04T01:13:37.505953+10:00 xev kernel: ---[ end trace 0000000000000000 ]--- 
2026-08-04T01:55:40.844110+10:00 xev kernel: pcieport 0000:00:03.3: AER: Multiple Correctable error message received from 0000:00:03.3 
2026-08-04T01:55:40.844130+10:00 xev kernel: pcieport 0000:00:03.3: PCIe Bus Error: severity=Correctable, type=Data Link Layer, (Receiver ID) 
2026-08-04T01:55:40.844132+10:00 xev kernel: pcieport 0000:00:03.3: device [8086:6f0b] error status/mask=00000040/00002000 
2026-08-04T01:55:40.844134+10:00 xev kernel: pcieport 0000:00:03.3: [ 6] BadTLP

2026-08-11T09:33:33.473855+10:00 xev kernel: amdgpu 0000:02:00.0: GPU fault detected: 147 0x00024802
2026-08-11T09:33:33.473871+10:00 xev kernel: amdgpu 0000:02:00.0: Process kscreenlocker_g pid 150905 thread kscreenloc:cs0 pid 150912
2026-08-11T09:33:33.473871+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_ADDR 0x00000800
2026-08-11T09:33:33.473873+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_STATUS 0x0F048002
2026-08-11T09:33:33.473873+10:00 xev kernel: amdgpu 0000:02:00.0: VM fault (0x02, vmid 7, pasid 63) at page 2048, write from 'TC0' (0x54433000) (72)
2026-08-11T09:33:33.473874+10:00 xev kernel: amdgpu 0000:02:00.0: GPU fault detected: 147 0x00004802
2026-08-11T09:33:33.473874+10:00 xev kernel: amdgpu 0000:02:00.0: Process kscreenlocker_g pid 150905 thread kscreenloc:cs0 pid 150912
2026-08-11T09:33:33.473875+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_ADDR 0x00000800
2026-08-11T09:33:33.473876+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_STATUS 0x0E048002
2026-08-11T09:33:33.473876+10:00 xev kernel: amdgpu 0000:02:00.0: VM fault (0x02, vmid 7, pasid 63) at page 2048, read from 'TC0' (0x54433000) (72)
2026-08-11T09:33:35.481863+10:00 xev kernel: amdgpu 0000:02:00.0: Dumping IP State
2026-08-11T09:33:35.481875+10:00 xev kernel: amdgpu 0000:02:00.0: Dumping IP State Completed
2026-08-11T09:33:35.481875+10:00 xev kernel: amdgpu 0000:02:00.0: [drm] AMDGPU device coredump file has been created
2026-08-11T09:33:35.481876+10:00 xev kernel: amdgpu 0000:02:00.0: [drm] Check your /sys/class/drm/card0/device/devcoredump/data
2026-08-11T09:33:35.481877+10:00 xev kernel: amdgpu 0000:02:00.0: GPU fault detected: 146 0x0110040c
2026-08-11T09:33:35.481877+10:00 xev kernel: amdgpu 0000:02:00.0: Process kscreenlocker_g pid 150905 thread kscreenloc:cs0 pid 150912
2026-08-11T09:33:35.481878+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_ADDR 0x00000022
2026-08-11T09:33:35.481879+10:00 xev kernel: amdgpu 0000:02:00.0: VM_CONTEXT1_PROTECTION_FAULT_STATUS 0x0E00400C
2026-08-11T09:33:35.481879+10:00 xev kernel: amdgpu 0000:02:00.0: VM fault (0x0c, vmid 7, pasid 63) at page 34, read from 'TC3' (0x54433300) (4)
2026-08-11T09:33:35.489845+10:00 xev kernel: amdgpu 0000:02:00.0: ring gfx timeout, signaled seq=5123619, emitted seq=5123621
2026-08-11T09:33:35.489853+10:00 xev kernel: amdgpu 0000:02:00.0: Process kscreenlocker_g pid 150905 thread kscreenloc:cs0 pid 150912
2026-08-11T09:33:35.489854+10:00 xev kernel: amdgpu 0000:02:00.0: GPU reset begin!. Source: 1
2026-08-11T09:33:35.493839+10:00 xev kernel: amdgpu 0000:02:00.0: [drm] ERROR Failed to initialize parser -125!
2026-08-11T09:33:35.737848+10:00 xev kernel: amdgpu: cp is busy, skip halt cp
2026-08-11T09:33:35.897842+10:00 xev kernel: amdgpu: rlc is busy, skip halt rlc
2026-08-11T09:33:35.897852+10:00 xev kernel: amdgpu 0000:02:00.0: BACO reset
2026-08-11T09:33:36.485849+10:00 xev kernel: amdgpu 0000:02:00.0: GPU reset succeeded, trying to resume
2026-08-11T09:33:36.485859+10:00 xev kernel: amdgpu 0000:02:00.0: [drm] PCIE GART of 256M enabled (table at 0x000000F402000000).
2026-08-11T09:33:36.485860+10:00 xev kernel: amdgpu 0000:02:00.0: VRAM is lost due to GPU reset!

Aug 11 17:01:47 ami kernel: ------------[ cut here ]------------
Aug 11 17:01:47 ami kernel: xe 0000:23:00.0: [drm] DMC 1 mmio[0]/0x5f074 incorrect (expected 0x96fc0, current 0x0)
Aug 11 17:01:47 ami kernel: WARNING: drivers/gpu/drm/i915/display/intel_dmc.c:696 at assert_dmc_loaded+0x275/0x430 [xe], CPU#0: kworker/0:3/215
Aug 11 17:01:47 ami kernel: Modules linked in: intel_rapl_msr intel_rapl_common intel_uncore_frequency intel_uncore_frequency_common xe(+) skx_edac snd_h>
Aug 11 17:01:47 ami kernel:  msr i2c_dev configfs efi_pstore efivarfs autofs4 btrfs libblake2b raid6_pq xor mpt3sas raid_class scsi_transport_sas megarai>
Aug 11 17:01:47 ami kernel: CPU: 0 UID: 0 PID: 215 Comm: kworker/0:3 Not tainted 7.1.7+deb14-amd64 #1 PREEMPT(lazy)  Debian 7.1.7-1 
Aug 11 17:01:47 ami kernel: Hardware name: HP HP Z4 G4 Workstation/81C5, BIOS P61 v03.00 04/15/2026
Aug 11 17:01:47 ami kernel: Workqueue: sync_wq local_pci_probe_callback
Aug 11 17:01:47 ami kernel: RIP: 0010:assert_dmc_loaded+0x291/0x430 [xe]
Aug 11 17:01:47 ami kernel: Code: 24 10 e8 f2 e5 a3 ce 48 8d 3d bb 85 0d 00 8b 54 24 0c 45 89 e9 45 89 e0 48 89 c6 52 8b 4c 24 2c 51 8b 4c 24 30 48 8b 54>
Aug 11 17:01:47 ami kernel: RSP: 0018:ffffd27ac0b87b80 EFLAGS: 00010282
Aug 11 17:01:47 ami kernel: RAX: ffffffffc1743dfd RBX: ffff8c5b80e54000 RCX: 0000000000000001
Aug 11 17:01:47 ami kernel: RDX: ffff8c5b81df5a10 RSI: ffffffffc1743dfd RDI: ffffffffc1605860
Aug 11 17:01:47 ami kernel: RBP: ffff8c5b86955000 R08: 0000000000000000 R09: 000000000005f074
Aug 11 17:01:47 ami kernel: R10: 0000000000000000 R11: 0000000000091050 R12: 0000000000000000
Aug 11 17:01:47 ami kernel: R13: 000000000005f074 R14: 0000000000000001 R15: 0000000000000000
Aug 11 17:01:47 ami kernel: FS:  0000000000000000(0000) GS:ffff8c673e172000(0000) knlGS:0000000000000000
Aug 11 17:01:47 ami kernel: CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Aug 11 17:01:47 ami kernel: CR2: 00007ffed1fdcd00 CR3: 0000000ae942a003 CR4: 00000000003706f0
Aug 11 17:01:47 ami kernel: Call Trace:
Aug 11 17:01:47 ami kernel:  
Aug 11 17:01:47 ami kernel:  intel_dmc_enable_pipe+0xe4/0x290 [xe]
Aug 11 17:01:47 ami kernel:  ? drm_crtc_vblank_reset+0x4d/0x120 [drm]
Aug 11 17:01:47 ami kernel:  intel_modeset_setup_hw_state+0xb50/0x1e10 [xe]
Aug 11 17:01:47 ami kernel:  ? intel_display_driver_probe_nogem+0x138/0x1a0 [xe]
Aug 11 17:01:47 ami kernel:  intel_display_driver_probe_nogem+0x138/0x1a0 [xe]
Aug 11 17:01:47 ami kernel:  xe_display_init_early+0xb2/0x140 [xe]
Aug 11 17:01:47 ami kernel:  xe_device_probe+0x3c8/0xb50 [xe]
Aug 11 17:01:47 ami kernel:  ? xe_pm_init_early+0x152/0x160 [xe]
Aug 11 17:01:47 ami kernel:  xe_pci_probe+0xc26/0x1150 [xe]
Aug 11 17:01:47 ami kernel:  local_pci_probe+0x3e/0x90
Aug 11 17:01:47 ami kernel:  local_pci_probe_callback+0x16/0x20
Aug 11 17:01:47 ami kernel:  process_one_work+0x19d/0x3a0
Aug 11 17:01:47 ami kernel:  worker_thread+0x1af/0x320
Aug 11 17:01:47 ami kernel:  ? __pfx_worker_thread+0x10/0x10
Aug 11 17:01:47 ami kernel:  kthread+0xe3/0x120
Aug 11 17:01:47 ami kernel:  ? __pfx_kthread+0x10/0x10
Aug 11 17:01:47 ami kernel:  ret_from_fork+0x2b2/0x340
Aug 11 17:01:47 ami kernel:  ? __pfx_kthread+0x10/0x10
Aug 11 17:01:47 ami kernel:  ret_from_fork_asm+0x1a/0x30
Aug 11 17:01:47 ami kernel:  
Aug 11 17:01:47 ami kernel: ---[ end trace 0000000000000000 ]---

Debian Contributions: 2026-07 Contributing to Debian is part of Freexian s mission. This article covers the latest achievements of Freexian and their collaborators. All of this is made possible by organizations subscribing to our Long Term Support contracts and consulting services.

DebConf 26 organization, by Lucas Kanashiro, Santiago Ruano Rinc n, Stefano Rivera and Antonio Terceiro The 27th Annual Debian Conference was held in Santa Fe, Argentina, and several Freexian fellows were quite busy by being involved in the organization team.

• Santiago continued helping with duties related to the local team, e.g. preparing or proof-reading some announcements, reviewing the proposed food and the menus for the different diet required.
• During the conference, Kanashiro and Santiago also carried over tasks related to the content of the conference, including updating the schedule as it became necessary during the event.
• Stefano worked within the core video team, setting up equipment in talk rooms and coordinating the live video streaming. Stefano also supported the front desk and local organisers as a website developer and conference book-keeper.
• Antonio kept working on website maintenance, specially in support of the content team. During DebConf he also ran a hands-on workshop to help interested contributors get started with developing the DebConf websites.

d-i VLAN support, by Colin Watson In environments that use IEEE 802.1Q VLANs, some hosts (such as routers attached to trunk ports) may need to apply VLAN tags themselves rather than relying on switches to do so. There has been a long-running request to add support for these to the Debian installer with a proposed patch set put together by several people over the years, and a Freexian customer asked us to help get this over the line. Colin reviewed the latest version of the patch set, applied a number of corrections, added Netplan support, spent some time testing a variety of possible paths through the installer, and landed this. There s also now documentation for this in the next version of the installation guide.

Miscellaneous contributions

• Carles wrote documentation for installing Mailman3 and migrating from Mailman2. Added it into Mailman3 upstream documentation.
• Carles, using po-debconf-manager: reviewed 2 packages, submitted 2 packages
• Carles organized Catalan translation update. Created a Debian Wiki page to have an overview of the work / coordination during next months. Reviewed and submitted some pages.
• Carles improved the documentation for building the debian.org Web in MR 1154 and MR 1557. Fixed debian-reference documentation. Added sections on Mutt Wiki page (handling of mailto, viewing HTML parts web browser), update and improve bash-completion Wiki page. Added a troubleshooting section in Signal Wiki.
• Thorsten did another upload of hplip to fix RC bugs. He also spent some time taking care of older bugs. Most of the time such bugs had been fixed in a previous upload but haven t been closed in the BTS. He also uploaded a new upstream version of foomatic-db. Last but not least, he gave some user support with the package epson-inkjet-printer-escpr. There seems to be a new software available for Epson printers. Unfortunately the license is not compatible with DFSG and so this software will never make it into Debian.
• During DebCamp 26, the Golang team had a dedicated Sprint to transition the Golang toolchain (namely on dh-golang) to make builds aware of the module defined upstream with the aim of solving important issues. To help in these efforts, Santiago made changes in the Salsa CI pipeline and documented on how to use it to check if a package requires adjustments after the toolchain update.
• Santiago continued co-mentoring Aryan Karamtoth on the Linux livepatching project, specifically providing feedback about the implementation of dlp-tools.
• Stefano reviewed and merged a migration of Debian reimbursements from wkhtmltopdf to weasyprint, unblocking an upgrade to Debian trixie.
• Stefano s cPython upstream merge request adding multiarch tags to stable ABI extensions was finally merged.
• Stefano iterated on his upstream cPython merge request to add CI coverage for Debian s multi-arch expectations.
• Stefano uploaded Python 3.15.0 beta 4 to Debian experimental.
• Stefano uploaded Python 3.13 to trixie, fixing a regression in a previous trixie point update he made.
• Helmut continued to report undeclared file conflicts.
• Helmut sent patches for three cross build failures.
• Helmut proposed a MR to port piuparts to pathlib.
• Antonio has done quite some work on Debian CI, including rebuilding the Debian CI armhf/armel worker VMs, and releasing debci 4.2, implementing a backup scheme, and several improvements to the codebase such as improving the incus-lxc backend in preparation for switching to the upcoming switch to using it by default as announced in the latest bits from the ci.debian.net operators.
• Emilio helped with transitions, particularly with Python 3.14 as default and Perl 5.42. During the Perl transition, an issue was identified with how britney schedules autopkgtests for binNMUs, and that testing was reverted for the time being.
• Colin restructured openssh-* binary packages to better support the upcoming GSS-API package split. This caused several autopkgtest regressions in other packages because openssh-server no longer depends on openssh-client, all of which have fixes either pending review or merged now.
• Lucas started a discussion around the creation of a Debian packaging video course for newcomers in the context of the Outreach team.
• Lucas reviewed some contributions to ruby3.4 and provided feedback.
• Anupa worked with Jean-Pierre Giraud on the point release announcements for Debian 13.6 and Debian 12.15.
• Anupa joined Jean-Pierre Giraud to prepare the Micronews for DebConf 26 press coverage.