LWN has had a number of articles on immutable distributions, such as Bluefin and Bazzite, in recent years. These distributions have taken a variety of approaches, including using rpm-ostree, filesystem snapshots, and bootable container (bootc) images. But those approaches, especially the latter, lead to extra complexity for a user attempting to install new software, instead of just using the existing package manager. AshOS (Any Snapshot Hierarchical OS) is an experimental AGPL-3-licensed "meta-distribution" that tried a different approach more in line with traditional package management. Although the project is no longer updated, it remains usable, and can still shed some light on a potential alternate path for users worried about adopting bootc-based approaches.

While there are several rootkits that target Linux, they have so far not fully embraced the open-source ethos typical of Linux software. Luckily, Matheus Alves has been working to remedy this lack by creating an open-source rootkit called Singularity for Linux systems. Users who feel their computers are too secure can install the Singularity kernel module in order to allow remote code execution, disable security features, and hide files and processes from normal administrative tools. Despite its many features, Singularity is not currently known to be in use in the wild — instead, it provides security researchers with a testbed to investigate new detection and evasion techniques.

Quality-of-service (QoS) mechanisms attempt to prioritize some processes (or network traffic, disk I/O, etc.) over others in order to meet a system's performance goals. This is a difficult topic to handle in the world of Linux, where workloads, hardware, and user expectations vary wildly. Qais Yousef spoke at the 2025 Linux Plumbers Conference, alongside his collaborators John Stultz, Steven Rostedt, and Vincent Guittot, about their plans for introducing a high-level QoS API for Linux in a way that leaves end users in control of its configuration. The talk focused specifically on a QoS mechanism for the scheduler, to prioritize access to CPU resources differently for different kinds of processes. (slides; video)

The Software Freedom Conservancy (SFC) is suing VIZIO over smart TVs that include software licensed under the GPL and LGPL (including the Linux kernel, FFmpeg, systemd, and others). VIZIO didn't provide the source code along with the device, and on request they only provided some of it. Unlike a typical lawsuit about enforcing the GPL, the SFC isn't suing as a copyright holder; it's suing as a normal owner of the TV in question. This approach opens some important legal questions, and after years of pre-trial maneuvering (most recently resulting in a ruling related to signing keys that is the subject of a separate article), we might finally obtain some answers when the case goes to trial on January 12. As things stand, it seems likely that the judge in the case will rule that that the GPL-enforcement lawsuits can be a matter of contract law, not just copyright law, which would be a major change to how GPL enforcement works.

The nature and role of the Linux Foundation's Technical Advisory Board (TAB) is not well-understood, though a recent LWN article shed some light on its role and history. At the 2025 Linux Plumbers Conference (LPC), the TAB held a question and answer session to address whatever it was the community wanted to know (video). Those questions ended up covering the role of large language models in kernel development, what it is like to be on the TAB, how the TAB can help grease the wheels of corporate bureaucracy, and more.

Aleksa Sarai, as the maintainer of the runc container runtime, faces a constant battle against security problems. Recently, runc has seen another instance of a security vulnerability that can be traced back to the difficulty of handling file paths on Linux. Sarai spoke at the 2025 Linux Plumbers Conference (slides; video) about some of the problems runc has had with path-traversal vulnerabilities, and to ask people to please use libpathrs, the library that he has been developing for safe path traversal.

The BPF verifier works, on a theoretical level, by considering every possible path that a BPF program could take. As a practical matter, however, it needs to do that in a reasonable amount of time. At the 2025 Linux Plumbers Conference, Mahé Tardy and Paul Chaignon gave a detailed explanation (slides; video) of the main mechanism that it uses to accomplish that: state pruning. They focused on two optimizations that help reduce the number of paths the verifier needs to check, and discussed some of the complications the optimizations introduced to the verifier's code.

The BPF verifier is complicated. It needs to check every possible path that a BPF program's execution could take. The fact that its determination of whether a BPF program is safe is based on the whole lifetime of the program, instead of simple local factors, means that the cause of a verification failure is not always obvious. Ihor Solodrai and Jordan Rome gave a presentation (slides) at the 2025 Linux Plumbers Conference in Tokyo about the BPF verifier visualizer that they have been building to make diagnosing verification failures easier.

The Internet Engineering Task Force (IETF) is the standards body responsible for the TLS encryption standard — which your browser is using right now to allow you to read LWN.net. As part of its work to keep TLS secure, the IETF has been entertaining proposals to adopt "post-quantum" cryptography (that is, cryptography that is not known to be easily broken by a quantum computer) for TLS version 1.3. Discussion of the proposal has exposed a large disagreement between participants who worried about weakened security and others who worried about weakened marketability.

Emma Smith and Kirill Podoprigora, two of Python's core developers, have opened a discussion about including Rust code in CPython, the reference implementation of the Python programming language. Initially, Rust would only be used for optional extension modules, but they would like to see Rust become a required dependency over time. The initial plan was to make Rust required by 2028, but Smith and Podoprigora indefinitely postponed that goal in response to concerns raised in the discussion.

Loris Cro has published a detailed YouTube video talking about the terminology used to discuss asynchronicity, concurrency, and parallelism in our recent article about Zig's new Io interface. Our article is not completely clear because it uses the term "asynchronous I/O" to refer to what should really be called "non-blocking I/O", and sometimes confuses asynchronicity for concurrency, among other errors of terminology, he says. Readers interested in precise details about Zig's approach and some of the motivation behind the design may find Cro's video interesting.

The designers of the Zig programming language have been working to find a suitable design for asynchronous code for some time. Zig is a carefully minimalist language, and its initial design for asynchronous I/O did not fit well with its other features. Now, the project has announced (in a Zig SHOWTIME video) a new approach to asynchronous I/O that promises to solve the function coloring problem, and allows writing code that will execute correctly using either synchronous or asynchronous I/O.

Greg Kroah-Hartman has announced the release of the 6.17.9, 6.12.59, and 6.6.117 stable kernels. As usual, he advises users of stable kernels to upgrade.