Kerla
Kerla is a monolithic operating system kernel written from scratch in Rust which aims to be compatible with the Linux ABI, that is, it runs Linux binaries without any modifications.
- Implements *NIX process concepts: context switching, signals,
fork(2),execve(2),wait4(2), etc. - Supports commonly used system calls like
write(2),stat(2),mmap(2),pipe(2),poll(2), ... - No disk support for now: initramfs is mounted as the root file system.
- Pseudo file systems: tmpfs and devfs.
- smoltcp-based TCP/IP support.
- Implements tty and pseudo terminal (pty).
- Supports QEMU and Firecracker (with virtio-net device driver).
- Supports x86_64.
- Docker-based initramfs build system.
Check out my blog post for motivation and my thoughts on writing an OS kernel in Rust.
Demo: SSH into Kerla!
You can play with Kerla over ssh. Your login is not visible from others (except me): we automatically launch a dedicated microVM on Firecracker for each TCP connection.
$ ssh [email protected]
If you found bugs or missing features, let me know on GitHub issues :)
Running a Docker Image (experimental)
You can run a Docker image as a root file system (not as a container!) on Kerla Kernel instead of our initramfs built from initramfs directory.
For example, to run nuta/helloworld image (Dockerfile), try the following command:
$ make IMAGE=nuta/helloworld run
...
[ 0.029] syscall: execve(439398, 4393b8, 4393c8, 8, 2f2f2f2f2f2f2f2f, 8080808080808080)
[ 0.030] syscall: arch_prctl(1002, 4055d8, 0, 20000, 0, ff)
[ 0.031] syscall: set_tid_address(4057f0, 4055d8, 0, 20000, 0, ff)
[ 0.033] syscall: ioctl(1, 5413, 9ffffeed0, 1, 405040, 9ffffeef7)
_ _ _ _ _ _
| |__ ___| | | ___ __ _____ _ __| | __| | |
| '_ \ / _ \ | |/ _ \ \ \ /\ / / _ \| '__| |/ _` | |
| | | | __/ | | (_) | \ V V / (_) | | | | (_| |_|
|_| |_|\___|_|_|\___/ \_/\_/ \___/|_| |_|\__,_(_)
This feature is in a very early stage and I guess almost all images out there won't work because:
- They tend to be too large to be embedded into the kernel image.
- They might use unimplemented features (e.g. position-independent executables used in Alpine Linux).
Building and Running the OS
See Quickstart for instructions on building from source, running on emulators, etc.
Current Roadmap
Roadmap - Run a Node.js Web Application on Kerla on Firecracker on AWS
Compatibility
See here for the current status.
Contributing
Send me bug reports, feature requests, and patches on GitHub for example:
- Implementing missing features: majority of existing Linux applications won't work due to the lack of features.
- Writing documentation: I think Kerla could be good material to learn how an operating system kernel works.
- Trying to experiment with Rust-y ideas: for example currently I'm interested in GhostCell.
License
See LICENSE.md.
Related Work
Emulating Linux ABI is not a novel work. Some UNIX-like kernels like FreeBSD and NetBSD already have their own Linux emulation layers. Windows has a well-known feature called Windows Subsystem for Linux (WSL) which enables running Linux binaries seamlessly. WSL 1 implements the feature by ABI emulation. WSL 2 runs the real Linux kernel using the hardware-accelerated virtualization (Hyper-V).
Aside from general-purpose operating systems, there're some attractive projects related to the Linux ABI emualtion. OSv is a unikernel which runs unmodified Linux binaries. rCore is a teaching operating system which implements the Linux ABI in Rust. Noah suggests an intriguing approach to run unmodified Linux binaries on macOS.