Linux Archive

Lennart Poettering, main developer of systemd, has announced run0, a systemd-based replacement for the well-known sudo command that fixes many of he inherent issues with the widely used tool to gain temporary elevated privileges. There are various problems with sudo, which basically come down to that it’s a large SUID binary, meaning it consists of privileged code that unprivileged users can run from their own context. This makes sudo a fairly large attack surface, and why OpenBSD uses doas instead; while doas suffers from the same main problem, it’s much smaller and reduces the attack surface considerably. SUID processes are weird concepts: they are invoked by unprivileged code and inherit the execution context intended and controlled by unprivileged code. By execution context I mean the myriad of properties that a process has on Linux these days, from environment variables, process scheduling properties, cgroup assignments, security contexts, file descriptors passed, and so on and so on. A few of these settings the kernel is nice enough to clean up automatically when a SUID binary is invoked, but much of it has to be cleaned up by the invoked suid binary. This has to be done very very carefully, and history has shown that SUID binaries are generally pretty shit at that. ↫ Lennart Poettering Poettering wants to address this problem, and has come up with run0, which behaves like sudo, but works entirely differently and is not SUID. Run0 asks the services manager to create a shell or command under the target user’s ID, creating a new PTY, sending data back and forth from the originating TTY and the new PTY. Or in other words: the target command is invoked in an isolated exec context, freshly forked off PID 1, without inheriting any context from the client (well, admittedly, we *do* propagate $TERM, but that’s an explicit exception, i.e. allowlist rather than denylist). One could say, “run0” is closer to behaviour of “ssh” than to “sudo”, in many ways. Except that it doesn’t bother with encryption or cryptographic authentication, key management and stuff, but instead relies on the kernel’s local identification mechanisms. run0 doesn’t implement a configuration language of its own btw (i.e. no equivalent of /etc/sudoers). Instead, it just uses polkit for that, i.e. how we these days usually let unpriv local clients authenticate against priv servers. ↫ Lennart Poettering This approach addresses a whole slew of attack vectors on sudo, and it comes with fun additional features like being able to give your terminal a different background tint when using it, or displaying a little red dot in the terminal window title to further indicate you’re using elevated privileges. It will ship as part of the upcoming release of systemd 256.

In February last year I wrote about running a FreeBSD desktop, and concluded that sometimes you need to give yourself permission to tinker. Well recently I’ve started tinkering with Alpine Linux! It’s been recommended to me for years, so I’m finally getting around to checking it out. There’s a lot to like if you come from BSD, which we’ll dig into here. ↫ Ruben Schade Just a quick look at this unexpectedly popular Linux distribution that really has its own identity.

Linus Torvalds really doesn’t like spaces – as in, tabs vs. spaces – and got a little annoyed that a commit removed a hidden tab because it “apparently showed breakage in some third-party kernel config parsing tool”. So, Torvalds decided to add some hidden tabs to trigger breakages like this, and is threatening to add more hidden tabs if necessary. It wasn’t clear what tool it was, but let’s make sure it gets fixed. Because if you can’t parse tabs as whitespace, you should not be parsing the kernel Kconfig files. In fact, let’s make such breakage more obvious than some esoteric ftrace record size option. If you can’t parse tabs, you can’t have page sizes. ↫ Linus Torvalds I’m not a programmer so I’m not going to wade into this debate – I have a personal Mastodon account to state it’s obviously tabs – but I did note that it seems like, at least in this commit message, Torvalds uses a double space after a period. Which is objectively the worst thing, right before Fahrenheit.

GestureX enables you to control your Linux PC using hand gestures. You can assign specific commands or functionalities to different hand gestures, allowing for hands-free interaction with your computer. ↫ GestureX GitHub page I personally see no use for any of this, but I’m sure there are some interesting accessibility uses for technology like this, which in and of itself make it a worthwhile endeavour to work on. Do note, though, that this is all beta, so there’s bound to be issues.

It’s the ext2 filesystem driver that will be marked as deprecated in the upcoming 6.9 Linux kernel. The main issue is that even if the filesystem is created with 256 byte inodes (mkfs.ext2 -I 256), the filesystem driver will stick to 32 bit dates. Because of this, the driver does not support inode timestamps beyond 03:14:07 UTC on 19 January 2038. ↫ Michael Opdenacker Kernel developer Ted T’so did state that if someone wants to add support for 64bit dates to ext2, it shouldn’t be too hard. I doubt many people still use ext2, but if someone is willing to step up, the deprecation can be made undone by adding this support.

Monogon OS is an open-source, secure, API-driven and minimal operating system unlike any other. It is based on Linux and Kubernetes, but with a clean userland rebuilt entirely from scratch. It is written in pure Go and eliminates decades worth of legacy code and unnecessary complexity. It runs on a fleet of bare metal or cloud machines and provides users with a hardened, production ready Kubernetes, without the overhead of traditional Linux distributions or configuration management systems. It does away with the scripting/YAML duct tape and configuration drift inherent to traditional deployments. Instead, it provides a stable API-driven platform free of vendor lock-in and with none of the drudgery. ↫ Monogon OS website This not exactly in my wheelhouse, but I’m pretty sure some of you will be all over this concept.

One of the limitations of AMD’s open-source Linux graphics driver has been the inability to implement HDMI 2.1+ functionality on the basis of legal requirements by the HDMI Forum. AMD engineers had been working to come up with a solution in conjunction with the HDMI Forum for being able to provide HDMI 2.1+ capabilities with their open-source Linux kernel driver, but it looks like those efforts for now have concluded and failed. ↫ Michael Larabel So dumb.

For the past few months we have been working hard to provide a fast, reliable and secure KVM backend for VirtualBox. VirtualBox is a multi-platform Virtual Machine Monitor (VMM) with a great feature set, support for a wide variety of guest operating systems, and a consistent user interface across different host operating systems. Cyberus Technology’s KVM backend allows VirtualBox to run virtual machines utilizing the Linux KVM hypervisor instead of the custom kernel module used by standard VirtualBox. Using KVM comes with a number of benefits. ↫ Florian Pester, Markus Partheymüller Excellent news. Dealing with the VirtualBox and VMware kernel modules can be a hassle if you’re using newer or custom kernels, and having the VirtualBox UI for kvm instead of things virt-manager is not something I’m unhappy about.

What follows is a letter from Hans Reiser to myself, which he wrote some two months back, and has asked me to publish, with his thoughts on the deprecation of ReiserFS from the Linux kernel. I have transcribed it to the best of my ability. Plaintext email may not be the best way to read it, as such, I have also made available PDF and HTML versions of the letter. ↫ Fredrick R. Brennan Hans Reiser is the creator of the ReiserFS file system, which used to be a serious contender for the Linux file system you’d use in the early 2000s. In 2006, Hans Reiser murdered his wife, and is currently serving a prison sentence for this crime. Hopefully, after he completes his prison sentence, he can become a contributing member of society once again, if the professionals and specialists involved in such matters deem him capable of doing so. The long letter mentioned here was actually quite a fascinating read, and details his abrasive behaviour in the Linux world, the design of ReiserFS and its place in the ecosystem at the time, and his thoughts on the removal of ReiserFS from the Linux kernel.

Flakes also are a symptom or cause of much intra-community strife between “pro-flakes” and “anti-flakes” factions, but this situation is at some level a sign of broken consensus processes and various actors trying to sidestep them, an assumption by many people that the docs are “outdated” for not using flakes, and the bizarre proliferation of flakes everywhere in blog posts or tutorials leading to a belief that they are required for everything. This post is about how to architect Nix projects in general, with a special eye on how to do so with flakes while avoiding their limitations. It tries to dispel misconceptions that can develop in such a monoculture. ↫ Jade Every time I hear about Nix and Flakes I feel like I understand all of it a little less.

Linux 6.7 has many exciting features including initial support for the Bcachefs file-system, Intel Meteor Lake graphics are stable as is the rest of the MTL platform support, initial NVIDIA GSP firmware support with the Nouveau driver, retiring of Intel Itanium support, and other new features with Linux 6.7. ↫ Michael Larabel The end of Itanium support is unforgivable. Itanium is the future, and Linux will miss the boat.

SteamOS 3 (“Holo”) is the Arch-based Linux distribution built for the Steam Deck, Valve Software’s portable PC gaming device. It’s a very interesting Linux distribution even when you only focus on how it updates itself: updates are performed atomically by downloading a new read-only root filesystem to an inactive partition, then rebooting into that partition. But consumers can also run steamos-devmode to unlock the root filesystem, put the pacman database in working order, and give them a working Linux distro with a normal package manager. This A/B atomic updates system is pretty standard for OSes these days, but there’s a lot going on in SteamOS that makes them work even with heavy customization by the end-user. I wanted to explore that while still being able to make changes to the root filesystem images. steamos-devmode is the easy way out; I wanted to make a proper fork. Here’s how I did it. ↫ iliana etaoin This article has sparked my interest to build a living room PC for Steam gaming for my wife and I, so we can play couch coop Steam games on an actual couch instead of behind our PC desk. Very detailed and in-depth, this article also teaches a lot about how SteamOS works under the hood.

PipeWire 1.0 now has all the features that are expected to move media streams inside a system. It takes advantage of advanced features of the Linux kernel to provide low latency, low footprint, and high performance while being secure. It is the perfect tool to build an embedded system or to securely share streams between containers. Linux audio and video has come a long way, and PipeWire is part of that. Excellent work.

Phoronix listed some of the major work happening in 6.7 for the RISC-V architecture: Merged last week was support for cbo.zero in user-space, support for CBOs on ACPI-based RISC-V systems, support for software shadow call stacks, improvements for the T-Head cache flushing operations, and other clean-ups and fixes. Meanwhile sent out today was a secondary pull request of more RISC-V changes for Linux 6.7. This latest pull has support for handling misaligned accesses in S-mode, performance improvements for TLB flushing, support for many new relocations in the module loader, and other enhancements. Momentum is definitely going for RISC-V.