Hacker News (100+) - 03 Oct 2026

What's FTL?

- You can build your own OS as a library. This userspace OS design makes it easy to add features, debug, upgrade the OS safely, as if writing applications.

- FTL kernel isolates containers (userspace OS instances) better than existing monolithic kernels, with a hypervisor-like interface based on a lightweight hardware-based isolation (user mode). You don't need bare-metal machines.

- FTL is compatible with Linux binaries. For example, the Rust-based HTTP server serving this website is a Linux application running on FTL. You can also run Unikernel-like specialized applications without POSIX abstractions.

How it works

Each container runs a userspace OS. It is a shared library which implements most of OS concepts such as Linux process, VFS, and TCP/IP. FTL kernel provides a minimal interface to implement Linux system calls in userspace, just like a hypervisor.

FTL combines the best of microkernels (flexible & secure) and monolithic kernels (performant & simple). Our goal is to make lightweight containers as secure as VMs, and unlock new OS-level abilities in applications, without sacrificing performance:

FTL Linux

Linux Linux Linux Linux

Process Process Process Process

Linux system calls

Userspace OS Linux's interface

(Process, VFS, TCP, ...)

Linux Kernel

minimal interface

process, fork/exec, memory,

FTL Kernel signals, TCP/IP, /proc,

vCPU, memory, drivers, ... /dev, drivers ...

Userspace OS design also enables you to extend most of Linux kernel features without kernel/eBPF programming. You can add printfs, apply security updates, and add new features quickly and safely. In FTL, OS is just a library. Read more.

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Original: https://ftl-os.org/