FTL
FTL is a new operating system aiming to be an alternative OS in cloud environments to Linux/BSDs/Illumos.
Container #1 (Linux compat) Container #2 (custom OS)
┌────────────────────────────────┐ ┌─────────────────┐
│ VM space VM space │ │ VmSpace │
│ ┏━━━━━━━━━━━━┓ ┏━━━━━━━━━━━━┓ │ │ ┏━━━━━━━━━━━━━┓ │
│ ┃ ┃ ┃ ┃ │ │ ┃ ┃ │
│ ┃ Linux ┃ ┃ Linux ┃ │ │ ┃ FTL native ┃ │
│ ┃ Process ┃ ┃ Process ┃ │ │ ┃ unikernel ┃ │
│ ┃ ┃ ┃ ┃ │ │ ┃ ┃ │
│ ┃ ╌╌╌╌╌╌╌╌ Linux ABI ╌╌╌╌╌╌╌╌┃ │ │ ┃╌╌╌╌╌╌╌╌╌╌╌╌╌┃ │
│ ┃ Linux compat library ┃ │ │ ┃ Your own ┃ │
│ ┃ (Process, VFS, TCP, ...) ┃◀┄┄┐ │ ┃ custom OS ┃ │
│ ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛ │ ┆ │ ┗━━━━━━━━━━━━━┛ │
└────────────────────────────────┘ ┆ └─────────────────┘
┆ Minimalistic system calls ┆
▼ ┆ user faults (syscalls)
╔════════════════════════════════════════════════════════╗
║ Small kernel ║
║ (memory, vCPU, network multiplexing, ...) ║
╚════════════════════════════════════════════════════════╝
- Secure: A small kernel provides minimalistic hypervisor-shaped system calls. OS features such as Linux system calls and TCP are implemented in a userspace library called userspace OS.
- Programmable: Key OS features are in a userspace library. You can write your OS just like unikernels, simply by patching the library (without kernel programming).
- Linux compatible: FTL aims to be a drop-in alternative to Linux in the cloud environment. Linux binary compatibilty layer is implemented as a library.
- Approachable: Easy-to-understand and testable codebase, handy end-to-end testing in TypeScript, and quick edit-compile-run cycle.
- Lightweight: Keep its footprint small to run even on constrained devices, and to develop the OS quickly.
Running locally
Install Rust toolchain, LLVM tools, and QEMU:
brew install rustup qemu # macOS
apt install rustup qemu-system # Ubuntu
Build and run:
./run.sh
You can start a specific Linux command:
./run.sh "/bin/echo Hello World"
To get an ISO image to run FTL on cloud:
ISO=1 ./build.sh
[!TIP]
Fun fact: ftl-os.org is served by FTL running on Google Compute Engine.
Design
Per-container userspace OS
Most of OS features such as the concept of Linux process is implemented in a userspace library, which we call "userspace OS". This design is similar to Exokernel where the traditional monolithic kernel features are moved to a userspace library (library OS).
FTL kernel provides hypervisor-like primitives: vCPU (thread), virtual address space (vmspace), virtual network, for example. The kernel does not interpret Linux system calls, and redirects them to the userspace OS's handler.
Each container instance has its own isolated userspace OS. This lets you run Linux containers on their own isolated Linux-like application kernels, similar to gVisor.
You can upgrade, add your own features, inject printfs for debugging, or optimize the userspace OS by simply starting a new container, without kernel programming or rebooting the machine.
Hypervisor-shaped kernel interface
FTL enables you to build your own OS best suited for your application. For example, the concept of Linux process is implemented in a userspace library, not in the kernel. VFS and TCP are also implemented in a library. This means the FTL kernel is more like a hypervisor, which multiplexes hardware resources and provides minimalistic interface like virtio.
FTL kernel interface is heavily inspired by hypervisors to narrow the attack surface, and to make userspace OS flexible. The difference from hypervisors is FTL uses the user mode to catch exceptions (not hardware-accelerated virtualization).
Linux compatibility layer
FTL is designed to support multiple personalities. The tier 1 personality is Linux which runs Linux executables without any modifications.
Foreign binary support (aka. ABI emulation) is a well-established technique that can be seen in modern operating systems, such as Windows Subsystem for Linux (WSL 1), FreeBSD's Linuxulator, and OSv, to name a few.
The key difference in FTL is that it is implemented as a userspace library, not as a in-kernel feature separate supervisor process. Each FTL container has its own isolated Linux-like application kernel.
We also aim to add our own personality to offer FTL's own system calls and features not available in Linux. That is, Linux ABI is just one of OS interfaces available on FTL.
Interceptors (planned)
Interceptor is a planned feature to control the behavior of OS components at runtime, just like middlewares in web frameworks. Rate limiting, security auditing, network packet routing, and live patching will be implemented as interceptors.
Batteries included
FTL will be more similar to BSD than Linux. We plan to provide FTL as an operating system bundled with userspace software integrated nicely.
License
FTL is dual-licensed under the MIT and Apache 2.0 licenses.
FTL 是一个用 Rust 编写的新型操作系统，目标是成为专门面向云环境的 Linux、BSD 和 Illumos 替代品。