FTL is a userspace OS design that lets you build your own OS as a library, making it easy to add features, debug, and upgrade safely. Its kernel isolates containers better than monolithic kernels using a hypervisor-like interface based on lightweight hardware-based isolation. No bare-metal machines are needed, and FTL is compatible with Linux binaries. For example, the Rust-based HTTP server serving this website runs on FTL. You can also run Unikernel-like specialized applications without POSIX abstractions.
Each container runs a userspace OS implemented as a shared library, handling Linux processes, VFS, and TCP/IP. The FTL kernel provides a minimal interface to implement Linux system calls in userspace, similar to a hypervisor. It combines the flexibility and security of microkernels with the performance and simplicity of monolithic kernels. The goal is to make lightweight containers as secure as VMs while unlocking new OS-level abilities in applications without sacrificing performance.
The userspace OS design allows extending most Linux kernel features without kernel or BPF programming. You can add printfs, apply security updates, and add new features quickly and safely. In FTL, the OS is just a library. The roadmap includes running a simple Linux HTTP server by September 2026, async Rust apps by October 2026, filesystem support in November 2026, Node.js/Go support in December 2026, and SMP, container images, and 64-bit Arm support by January 2027.
Source: Hacker News · Summarized by HeadlinesBriefing