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.

Version 6.20 of the Incus container and virtual-machine management system has been released. Notable changes in this release include a new standalone command to add IncusOS servers to a cluster, qcow2-formatted volumes for clustered LVM, and reverse DNS records in OVN. See the announcement for a full list of changes.

Everyone who interacts with Debian source code should be able to do so entirely in git.

That means, more specifically:

1. All examination and edits to the source should be performed via normal git operations.
2. Source code should be transferred and exchanged as git data, not tarballs. git should be the canonical form everywhere.
3. Upstream git histories should be re-published, traceably, as part of formal git releases published by Debian.
4. No-one should have to learn about Debian Source Packages, which are bizarre, and have been obsoleted by modern version control.

This is very ambitious, but we have come a long way!

So far, we have manually built and imported an initial set of 112 packages with the help of the packages in Debian Ports. This was enough to create an initial chroot and set up the first buildd which is now churning through the build queue. Over night, the currently single buildd instance already built and uploaded 300 new packages.

The FreeBSD Foundation has a blog post about the progress it has made in 2025 on the Laptop Support & Usability Project for FreeBSD. The foundation committed $750,000 to the project in 2025 and has made progress on graphics drivers, Wi-Fi 4 and 5 support, audio improvements, sleep states, and more.

The installer for FreeBSD has gained a couple of new features that benefit laptop users. In 15.0 the installer now supports downloading and installing firmware packages after the FreeBSD base system installation is complete. Coming in 15.1 it will be possible to install the KDE graphical desktop environment during the installation process. Grateful thanks to Bjoern Zeeb and Alfonso Siciliano respectively. [...]

The project continues into 2026 with a similar sized investment and scope. Key targets include completing work on sleep states (modern standby and hibernate), adding support for graphics drivers up to Linux 6.18, Wi-Fi 6 support, USB4 and Thunderbolt support, HDMI improvements, UVC webcam support, and Bluetooth improvements.

A substantial testing program will also start in January, aiming to test all the functionality together across a range of hardware. Community testers are very welcome to help out, the Foundation will release a blog post and send an invite to help to the Desktop mailing list some time in January 2026.

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.

I will be stepping down as Linux-Next maintainer on Jan 16, 2026. Mark Brown has generously volunteered to take up the challenge. He has helped in the past filling in when I have been unavailable, so hopefully knows what he is getting in to. I hope you will all treat him with the same (or better) level of respect that I have received.

It has been a long but mostly interesting task and I hope it has been helpful to others. It seems a long time since I read Andrew Morton's "I have a dream" email and decided that I could help out there - little did I know what I was heading for.

Over the last two decades or so, the kernel's development process has evolved from an unorganized mess with irregular releases to a smooth machine with a new release every nine or ten weeks. That would not have happened without linux-next; thanks are due to Stephen for helping to make the current process possible.

Systemd v259 has been released. Notable changes include a new "--empower" option for run0 that provides elevated privileges to a user without switching to root, ability to propagate a user's home directory into a VM with systemd-vmspawn, and more. Support for System V service scripts has been deprecated, and will be removed in v260. See the release notes for other changes, feature removals, and deprecated features.

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