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A modern experimental OS written from scratch in Rust to explore novel OS structure, state management techniques, and how to maximally leverage the power of language by shifting OS responsibilities into the compiler.

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Theseus OS

Theseus is a new OS written from scratch in Rust to experiment with novel OS structure, better state management, and how to shift OS responsibilities like resource management into the compiler.

We are continually working to improve the OS, including its fault recovery abilities for higher system availability without redundancy, as well as easier and more arbitrary live evolution and runtime flexbility. Though still an incomplete prototype, we envision that Theseus will be useful for high-end embedded systems or edge datacenter environments. See our published papers for more information about Theseus's design principles and implementation philosophy, as well as our goal to avoid the phenomenon of state spill or mitigate its effects as much as possible. Also, see Theseus's documentation for more.

Building Theseus

When you first check out the project, don't forget to checkout all the submodule repositories too:
git submodule update --init --recursive

Currently, we support building and running Theseus on the following host OSes:

  • Linux, 64-bit Debian-based distributions like Ubuntu, tested on Ubuntu 16.04, 18.04, 20.04.
    • Arch Linux has also been reported to work correctly.
  • Windows, using the Windows Subsystem for Linux (WSL), tested on the Ubuntu version of WSL and WSL2.
  • MacOS, tested on versions High Sierra (10.13) and Catalina (10.15.2).
  • Docker, atop any host OS that can run a Docker container.

Setting up the build environment

Linux or WSL (Windows Subsystem for Linux)

  • Update your system's package list:
    sudo apt-get update.
  • Install the following packages:
    sudo apt-get install nasm pkg-config grub-pc-bin mtools xorriso qemu qemu-kvm
    • Or on Arch Linux:
      sudo pacman -S nasm pkg-config grub mtools xorriso qemu

If you're on WSL, also do the following:

  • Install an X Server for Windows; we suggest using Xming.

  • Setup an X display as follows:

    • on WSL (version 1), run:
      export DISPLAY=:0.
    • on WSL2, run:
      export DISPLAY=$(cat /etc/resolv.conf | grep nameserver | awk '{print $2}'):0.

    You'll need to do this each time you open up a new WSL terminal, so it's best to add it to the end of your .bashrc file.

  • If you get this error:
    Could not initialize SDL(No available video device) - exiting
    then make sure that your X Server is running and that you have set the DISPLAY environment variable above.

  • Install a C compiler and linker toolchain, such as gcc.

  • NOTE: WSL and WSL2 do not currently support using KVM.


  • Install MacPorts and HomeBrew.
  • run the MacOS build setup script:
  • If things later go wrong, run
    rm -rf $HOME/theseus_tools_src $HOME/theseus_tools_opt /opt/local/bin/make
    and then start over.


Note: building and running Theseus within a Docker container may be slower than on a native host OS (e.g., QEMU+KVM).

  • Install Docker Engine. (Skip this if docker is already installed).
    We provide a convenience script for this on Ubuntu x86_64. Simply run:
    • After docker installs, enable your user account to run docker without root privileges:
      sudo groupadd docker; sudo usermod -aG docker $USER
      Then, log out and log back in (or restart your computer) for the user/group changes to take effet.
  • Build the docker image:
    This does not build Theseus, but rather only creates a docker image that contains all the necessary dependencies to build and run Theseus.
  • Run docker image locally as a container:
    Now you can run make run or other Theseus-specific build/run commands from within the docker container's shell.

Notes on Docker usage

  • The docker-based workflow should only require you to re-run the script multiple times (e.g., to re-build or run Theseus modifying its code). The docker installation and docker build steps are one-time only (though it won't hurt to run them again).
  • KVM doesn't currently work in docker. To run Theseus in QEMU using KVM, you can build Theseus within docker, exit the container, and then run make orun host=yes on your host machine.
  • When using docker, you can ignore the following section about installing Rust because our Dockerfile and scripts do it automatically.

Installing Rust

(Not needed if using Docker)

Install the current Rust compiler and toolchain by following the setup instructions here, which is just this command:
curl -sSf | sh

Building and Running

To build and run Theseus in QEMU, simply run:
make run

Run make help to see other make targets and the various options that can be passed to make.

Note: Rust compiler versions

Because we use the Rust nightly compiler (not stable), the Theseus Makefile checks to make sure that you're using the same version of Rust that we are. We were inspired to add this safety check when we failed to build other Rust projects put out there on Github because they used an earlier version of the nightly Rust compiler than what we had installed on our systems. To avoid this undiagnosable problem, we force you to use a specific version of rustc that is known to properly build Theseus; we also use the standard rust-toolchain file to ensure this. The Rust version is upgraded as often as possible to align with the latest Rust nightly, but this is a best-effort policy.

As such, if you see a build error about the improper version of rustc, follow the instructions displayed after the error message.

Using QEMU

QEMU allows us to run Theseus quickly and easily in its own virtual machine. To exit Theseus in QEMU, press Ctrl+Alt+G (or Ctrl+Alt on some systems), which releases your keyboard and mouse focus from the QEMU window. Then press Ctrl+C in the terminal window that you ran make run from originally to kill QEMU, or you can also quit QEMU using the GUI (x) button.

To investigate the hardware/machine state of the running QEMU VM, you can switch to the QEMU console by pressing Ctrl+Alt+2. Switch back to the main window with Ctrl+Alt+1. On Mac, manually select VGA or compact_monitor0 under View from the QEMU menu bar.

KVM Support

While not strictly required, KVM will speed up the execution of QEMU. To install KVM, run the following command:
sudo apt-get install kvm.
To enable KVM support, add host=yes to your make command, e.g.,
make run host=yes
This option is only supported on Linux hosts.


GDB has built-in support for QEMU, but it doesn't play nicely with OSes that run in long mode. In order to get it working properly with our OS in Rust, we need to patch it and build it locally. The hard part has already been done for us (details here), so we can just quickly set it up with the following commands.

First, install the following packages:
sudo apt-get install texinfo flex bison python-dev ncurses-dev

Then, from the base directory of the Theseus project, run this command to easily download and build it from an existing patched repo:
curl -sf | sh

After that, you should have a rust-os-gdb directory that contains the gdb executables and scripts.

Then, simply run make run_pause to build and run Theseus in QEMU, which will pause the OS's execution until we attach our patched GDB instance.
To attach the debugger to our paused QEMU instance, run make gdb in another terminal. QEMU will be paused until we move the debugger forward, with n to step through or c to continue running the debugger.
Try setting a breakpoint at the kernel's entry function using b nano_core::nano_core_start or at a specific file/line, e.g., b


Theseus, like the Rust language itself, includes two forms of documentation: the main source-level documentation within the code itself, and a "book" for high-level overviews of design concepts. The latter is a work in progress but may still be useful, while the former is more useful for developing on Theseus.

Documentation is currently hosted online here, but may be out of date. It's best to build it yourself, as detailed below.

Once your build environment is fully set up, you can generate Theseus's documentation in standard Rust format. To do so, simply run:
make doc

Or to view the documentation in a browser on your local machine:
make view-doc

There are similar commands for building the Theseus book:
make book

IDE Setup

Our personal preference is to use Visual Studio Code (VS Code), which has excellent cross-platform support for Rust. Other options are available here, but we don't recommend them.

For VS Code, recommended plugins are:

  • One of the following Rust language plugins. Disable the "all targets" option in either plugin's settings, such that the test target isn't used.
    • rust-analyzer, by matklad
    • Rust (RLS), by rust-lang
  • Better TOML, by bungcip
  • x86 and x86_64 Assembly, by 13xforever

Fixing Rustup, Rust Toolchain, or RLS Problems

Sometimes things just don't want to behave, especially if there were issues with the currently-chosen Rust nightly version. In that case, try the following steps to fix it:

  • Set your default Rust toolchain to the one version in the rust-toolchain file, for example:
    rustup default $(cat rust-toolchain).
  • With your newly-set default toolchain, add the necessary components:
    rustup component add rls rust-analysis rust-src.
  • In VS Code (or whatever IDE you're using), uninstall and reinstall the RLS extension, reloading the IDE each time.
  • Check your IDE's settings to make sure that no weird rust or RLS settings have been set; building Theseus doesn't require any special RLS settings.
  • If you're still having lots of issues, remove all other toolchains besides the default one and try again.
    You can see other installed toolchains with rustup toolchain list.


Booting on Real Hardware

We have tested Theseus on a variety of real machines, including Intel NUC devices, various Thinkpad laptops, and Supermicro servers. Currently, the only limiting factor is that the device support booting via USB or PXE using traditional BIOS rather than UEFI; support for UEFI is a work-in-progress.

To boot over USB, simply run make boot usb=sdc, in which sdc is the device node for the USB disk itself (not a partition like sdc2) to which you want to write the OS image. On WSL or other host environments where /dev device nodes don't exist, you can simply run make iso and burn the .iso file in the build/ directory to a USB, e.g., using Rufus on Windows.

To boot Theseus over PXE (network boot), see this set of separate instructions.


We would like to express our thanks to the OS Dev wiki and its community and to Philipp Oppermann's blog_os for serving as excellent starting points for Theseus. The early days of Theseus's development progress are indebted to these resources.


Theseus's source code is licensed under the MIT License. See the LICENSE-MIT file for more.


We adhere to similar development and style guidelines as the main Rust project.

PRs and issues are welcome from anyone; because Theseus is an experimental OS, certain features may be deprioritized or excluded from the main branch. Don't hesitate to ask or mention something though! 😄

More details to come.


A modern experimental OS written from scratch in Rust to explore novel OS structure, state management techniques, and how to maximally leverage the power of language by shifting OS responsibilities into the compiler.





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