TECHNOLOGY
New Project FTL Reimagines the OS as a Userspace Library for Cloud Containers
A new open-source project called FTL proposes running most operating system functions as a userspace library, aiming to give containers VM-like isolation without sacrificing performance.
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A newly surfaced open-source project called FTL is pitching a different way to build operating systems for cloud computing, moving core OS functions out of the kernel and into userspace libraries that run alongside each container.
According to its GitHub page, FTL lets each container run what the project calls a "userspace OS": a shared library implementing core operating system concepts such as Linux processes, a virtual file system, and TCP/IP networking. Rather than relying on a traditional monolithic kernel to handle these functions, FTL provides a minimal kernel interface, described as working "like a hypervisor," through which Linux system calls are implemented in userspace.
The project's stated goal is to combine strengths typically associated with two very different kernel designs. Microkernels are prized for flexibility and security, since they keep most OS code out of a privileged kernel; monolithic kernels, like Linux's, are valued for performance and simplicity. FTL's developers say they want lightweight containers that are as secure as full virtual machines while unlocking new OS-level capabilities for applications, all without the performance penalty usually associated with added isolation.
Because the OS logic lives in userspace rather than the kernel, FTL's creators say developers can extend Linux-like functionality without writing kernel code or eBPF programs. The project describes being able to add debug output, apply security patches, or introduce new features "quickly and safely," framing the operating system itself as simply another library an application links against.
FTL says it is compatible with existing Linux binaries. As a demonstration, the project notes that the website serving its own documentation is powered by a Rust-based HTTP server running as a Linux application on top of FTL. The system is also designed to support unikernel-style applications that skip POSIX abstractions entirely, isolating each container through lightweight, hardware-based user-mode protections rather than requiring dedicated bare-metal machines.
The project has published a roadmap extending into 2027, with early milestones already marked complete: a basic Linux HTTP server running on FTL, followed by support for asynchronous Rust applications using Linux threads and epoll. Upcoming goals include filesystem support, compatibility with Node.js and Go, and eventually symmetric multiprocessing, container image support, and 64-bit Arm compatibility.
The claims above come from FTL's own GitHub repository and an accompanying blog post, "Introducing FTL: A new operating system for clouds." As with many early-stage infrastructure projects announced through developer-focused channels like Hacker News, independent verification of its security and performance claims is not yet available, and readers should treat the project's self-reported benchmarks and roadmap as unverified until tested by outside parties.