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.
Roadmap
- September 2026: Run a simple Linux HTTP server on FTL (released in v0.0.1 ✅)
- October 2026: Async Rust apps support - Linux threads, epoll, ... (released in v0.1.0 ✅)
- November 2026: Filesystem
- December 2026: Node.js / Go support
- January 2027: SMP, container images, 64-bit Arm support
