Exploring the Next Generation of Rust-Powered Microkernels: Managarm, Asterinas, and Xous

Rumors of a Linux fork have resurfaced amid challenges such as Rust integration, new filesystems, developer conflicts, and systemd feature consolidation, but better alternatives exist.

Developer turnover is high: Rust maintainer Wedson Almeida Filho resigned, followed by Asahi Linux lead Hector Martin, GPU driver developer "Asahi Lina", and Alyssa Rosenzweig, indicating turbulence in kernel development.

The long‑awaited bcachefs has been demoted to external maintenance after a decade of work.

Recent work on GNU Hurd shows that microkernel efforts are still alive, and Minix 3 creator Andy Tanenbaum was honored with an award.

Managarm

Managarm is a multi‑platform microkernel OS that supports asynchronous processing across the system while maintaining compatibility with a large body of Linux software. It runs on x86‑64, Arm64, and is adding RISC‑V support. It supports SMP, ACPI, AHCI, NVMe, IPv4, Intel virtualization, QEMU, Wayland, X11, and hundreds of Linux binaries from GNU coreutils. It can even run games like Doom. The codebase is written in C++ and hosted on GitHub.

Asterinas

Asterinas is a radical new kernel that implements the Linux ABI but is written in Rust. It follows the "framekernel" design, which separates services from the kernel using Rust’s safety features; only a tiny core may contain unsafe Rust, while all OS services must be safe Rust, providing stronger memory safety.

The framekernel approach is compared to earlier projects such as RedLeaf OS (USENIX 14), SPIN (Modula‑3, 1990s) and HOUSE (Haskell). Modern Rust offers more momentum than those older languages, making the proposal to run existing binaries on a Rust‑based OS more attractive.

Xous

Xous is another Rust‑written microkernel, part of the larger Betrusted project. Unlike the others, it does not aim for Linux compatibility but focuses on its own hardware, the Precursor handheld device. Precursor ships with the Vault authentication app, which manages U2F/FIDO2, TOTP, and passwords, and can be used like a YubiKey for PC authentication.

Additional documentation includes the Xous Manual and the Betrusted wiki; Bunnie Huang’s blog provides further insights, especially on the PDDB (reasonably deniable database) concept.

Q&A

Q1: What special features does Managarm offer?

A: Managarm is a microkernel OS supporting asynchronous processing, extensive Linux software compatibility, multi‑platform operation (x86‑64, Arm64, upcoming RISC‑V), SMP, ACPI, AHCI, NVMe, IPv4, Wayland, X11, and hundreds of Linux binaries.

Q2: How does Asterinas differ from traditional microkernels?

A: Asterinas uses the framekernel design, separating services from the kernel via Rust’s language features. Only a minimal core may contain unsafe Rust; all other OS services must be written in safe Rust, enhancing memory safety.

Q3: What are the practical use cases for Xous?

A: Xous is part of the Betrusted project and runs on the shipped Precursor handheld device. Its flagship Vault app manages U2F/FIDO2, TOTP, and passwords, and the device can act as a pocket‑sized security token similar to a YubiKey.