Nix flake for mc-rtc and related project

June 2, 2026 · View on GitHub

🚧 Welcome to mc-rtc's nixpkgs flake
🚧 This repository is an ongoing effort of packaging the mc-rtc ecosystem under Nix
🚧 Flake API and overlay structure may change without notice

Current status:

Usage

Locally

Install Nix on your system
Install cachix
Enable the cachix cache (some user configuration)
Clone this repository
Navigate to the cloned folder
Run nix develop

Options

Options are provided through flakeModule to downstream packages

Override the shell's environment for local development

To override the default shell environment to use your own local version of a controller, you can do

mkdir -p nix-workspace/install nix-workspace/devel

now create a .direnv file with the following content

# Do not auto-update the flake, do so manually through nix-direnv-reload
# This avoids triggering potentially long compilations upon entering a shell
nix_direnv_manual_reload

# Use this flake
use flake https://github.com/mc-rtc/nixpkgs

# or use a local copy for development
# export MC_RTC_WITH_ROS=1
# export MC_RTC_USE_LOCAL=1
# use flake nixpkgs --impure # if you cloned it locally in ./nixpkgs

# Override LD_LIBRARY_PATH and PATH to use the local install folder for your custom controller
export LD_LIBRARY_PATH=$PWD/install/lib:$LD_LIBRARY_PATH
export LD_LIBRARY_PATH=$PWD/install/lib64:$LD_LIBRARY_PATH
export PATH=$PWD/install/bin:$PATH
# convenient cmake alias to ensure that the controller is installed in the expected local path
alias cmake_local="cmake -DCMAKE_PREFIX_PATH=$PWD/install -DMC_RTC_HONOR_INSTALL_PREFIX=ON -DCMAKE_BUILD_TYPE=RelWithDebInfo -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -G Ninja"

Then run direnv allow. Upon entering the nix-workspace folder, this will setup the environment for you.

Now if you wish to install a custom controller/...

cd nix-workspace/devel
git clone <your_controller>
cd <your_controller>

Create a .envrc file here

source_up
export MC_RTC_CONTROLLER_CONFIG="$PWD/../install/lib64/mc_controller/etc/mc_rtc.yaml:MC_RTC_CONTROLLER_CONFIG"

Then run direnv allow again. This will add your controller to the MC_RTC_CONTROLLER_CONFIG variable. To build:

mkdir build
cd build
cmake_local ..

Define your own superbuild

This is still a WIP, but the gist of it is:

define a derivation in your overlay containing all the derivations you wish to have available to mc-rtc. Runtime dependencies are passed to the robots/controllers/observers/plugins list and a corresponding mc_rtc.yaml containing the required library paths is auto-generated and added to MC_RTC_CONTROLLER_CONFIG env variable.

mc-rtc-superbuild-rolkneematics = final.mc-rtc-superbuild.overrideAttrs (old: {
  robots = [
    # note that panda-prosthesis is not strictly-speaking a robot, but it builds a robot module so we need it here as well to populate the robots runtime paths
    panda-prosthesis
    mc-panda-lirmm
    mc-panda
  ];
  controllers = [ panda-prosthesis ];
  # extra mc_rtc.yaml
  configs = [ "${panda-prosthesis}/lib/mc_controller/etc/mc_rtc.yaml" ];
  observers = [];
  plugins = [ panda-prosthesis mc-force-shoe-plugin ];
  apps = [ mc-rtc-magnum mc-franka mc-rtc-ticker sch-visualization ];
});

Full doc coming soon...

Run your own controller

# if cachix is setup correctly this should just pull binary dependencies. Otherwise
# it will build everything specified in the `mc-rtc-superbuild` derivation (and their depencencies)
nix develop
# or nix develop .#mc-rtc-superbuild-rolkneematics # if you want to use your own derivation
mc-rtc-magnum &
# By default mc_rtc_ticker will use the configuration provided by `MC_RTC_CONTROLLER_CONFIG` env variable
# This is set by the mc-rtc-superbuild derivation and devShell to contain all needed runtime depencencies
# and optionally a default controller's configuration
mc_rtc_ticker