3  Setting up Nix and Positron

3.1 Introduction

Nix officially supports only macOS and Linux distributions. Windows is technically supported via WSL2, since it runs a Linux kernel underneath. Practically, this means you can treat Linux distributions and Windows (via WSL2) as one system, and macOS as a separate system.

If you plan to use Nix on Windows, WSL2 must be installed and running first. An advantage of using WSL2 is isolation: any existing tools you have installed on Windows such as R, RStudio, Python, uv, etc., won’t interfere with Nix, allowing you to use it freely.

On Linux and macOS, however, pre-installed tools can conflict with Nix-managed tools. For example, environment managers like uv or manually installed R/Python versions may interfere with Nix environments. Ideally, you would let Nix manage all your tools, but completely removing existing installations of tools is often impractical especially if the machine you will be using to follow along is also the machine you use for work.

But I do highly recommend setting up Nix to manage everything, at least once you feel comfortable enough with Nix. However if you’re primarily an R user, you should be fine even with a system-level R installation, and you could just set up Nix on the same machine and there shouldn’t be any issue (if there are it’ll only be when trying to use Nix, not when trying to use your usual system-level installation of R).

Things can get more complicated with Python, especially if you have auto-loading of environments in your IDE.

If you prefer a safe way to experiment with Nix, you can set up a Linux virtual machine (but again, only if you are already on Linux or macOS, and only if the machine you will be using already has R or Python).

On macOS, you could use UTM¹ to set up such a machine. A simple virtualization program for Linux is Gnome Boxes². If you use those, I recommend you then get the Lubuntu iso and install Lubuntu. It’s a lightweight Ubuntu variant which is ideal for VMs. Give the VM 4 GB of RAM, and 50 GB of disk space to be safe.

You can then safely experiment in that machine without interfering with your work computer!

3.2 Windows pre-requisites

If you are on Windows, you need the Windows Subsystem for Linux 2 (WSL2) to run Nix. If you are on a recent version of Windows 10 or 11, you can simply run this as an administrator in PowerShell:

wsl --install

You can find further installation notes at this official Microsoft documentation.

We recommend to activate systemd in Ubuntu WSL2, mainly because this supports other users than root running Nix. To set this up, please do as outlined in the official Microsoft WSL documentation:

# in WSL2 Ubuntu shell

sudo -i
nano /etc/wsl.conf

This will open the /etc/wsl.conf in a nano, a command line text editor. Add the following line:

[boot]
systemd=true

Save the file with CTRL-O and then quit nano with CTRL-X. Then, type the following line in powershell:

wsl --shutdown

and then relaunch WSL (Ubuntu) from the start menu.

Then, you can follow the instructions for Linux.

3.3 Determinate Nix

Installing (and uninstalling) Nix is quite simple, thanks to the installer from Determinate Systems, a company that provides services and tools built on Nix.

Do not use your operating system’s package manager to install Nix. Instead, simply open a terminal and run the following line (on Windows, if you cannot or have decided not to activate systemd, then you have to append --init none to the command. You can find more details about this on The Determinate Nix Installer page):

curl --proto '=https' --tlsv1.2 -sSf \
    -L https://install.determinate.systems/nix | \
     sh -s -- install

This will install Nix in a matter of seconds! Restart the terminal (WSL or native on Linux) and let’s try our installation of Nix using so-called temporary shells.

3.4 Temporary shells

You now have Nix installed; before continuing, it let’s see if everything works (close all your terminals and reopen them) by dropping into a temporary shell with a tool you likely have not installed on your machine.

Open a terminal and run:

which sl

you will likely see something like this:

which: no sl in ....

now run this:

nix-shell -p sl

and then wait for Nix to do its magic. Then, run again:

which sl

this time you should see something like:

/nix/store/cndqpx74312xkrrgp842ifinkd4cg89g-sl-5.05/bin/sl

This is the path to the sl binary installed through Nix. The path starts with /nix/store: the Nix store is where all the software installed through Nix is stored.

Now type sl and see what happens!

You can find the list of available packages here.

3.5 The rstats-on-nix Cache

Next, we install the cachix client and configure our rstats-on-nix cache: this will install binary versions of many R packages which will speed up the building process of environments:

nix-env -iA cachix -f https://cachix.org/api/v1/install

then use the cache:

cachix use rstats-on-nix

You only need to do this once per machine you want to use {rix} on. Many thanks to Cachix for sponsoring the rstats-on-nix cache!

{rix} also includes a function called setup_cachix() which will configure the cache but it is recommended to use the cachix client instead. This is because setup_cachix() will not edit the files that require admin/root privileges and only edit the user-level files. This may not be enough depending on how you installed Nix. Using the cachix client takes care of everything. Use setup_cachix() when building a Docker image or if you somehow mess up the configuration file (which should be located in ~/.config/nix.conf).

On Linux, once Nix is installed, all the software that will be installed through Nix will be saved to the /nix directory on the root partition. It is common for Linux users to have a separate partition for /, which may be small. Complete development environments built with Nix can take up much space, so if the available space on your root partition is limited, we advise you to mount the /nix folder on another partition with more space (for example, a secondary hard drive). For this, edit /etc/fstab and add the following line at the end:

/home/path_to/nix /nix none bind 0 0

This will map /nix to /home/path_to/nix which can be on a larger partition. If you have enough space on your root partition, you can ignore the above instructions.

3.6 direnv

direnv will automatically load Nix shells when you open a project managed by Nix. This makes using Nix, especially with an editor (which we will configure in the next section), much more seamless and easy. If you’re using Windows, install direnv in WSL, just like Nix and cachix before. To install direnv run this command:

nix-env -f '<nixpkgs>' -iA direnv

Then, we highly recommend to install the nix-direnv extension:

nix-env -f '<nixpkgs>' -iA nix-direnv

It is not mandatory to use nix-direnv if you already have direnv, but it’ll make loading environments much faster and seamless.

Finally, if you haven’t used direnv before, don’t forget this last step to make your terminal detected and load direnv automatically. On WSL, need to add eval "$(direnv hook bash)" to a file called .bashrc, which you can find in your home/ directory (this is the directory that contains your user’s folder like Downloads and so on). This file starts with a ., which means it is hidden. You need top open it in an editor and add the line right at the bottom. If you’re comfortable with the terminal, you can do it right from WSL, if not, you can navigate to your WSL home directory from a Windows file explorer by typing \\wsl$ in the address bar, and then entering the ubuntu directory. Inside, you’ll see the home/ directory, and inside a directory named after your username. This is where .bashrc resides, and you can open it using Notepad.

On macOS, you need to add eval "$(direnv hook zsh) inside of .zshrc instead.

3.7 Installing and configuring an editor

3.7.1 Positron and VS Code

For polyglot data science projects, the recommended editor is Positron. Positron is a fork of VS Code tailored for data scientists, with first-class support for both R and Python. It makes it straightforward to select the correct interpreter for each project, whether managed by Nix or another solution. Being cross-platform, the same setup works on macOS, Windows, and Linux. Since it is based on VS Code, switching from VS Code to Positron is seamless.

Personally, I use Emacs, but Positron is more accessible for most users. If you prefer, you can also configure VS Code directly; instructions are provided below.

Installing Positron:

• Download and install the installer for your operating system.
• On Windows, even if Nix is installed under WSL, install the Windows version of Positron. It can interact with Nix on WSL via a plugin.
• In Positron, install the direnv extension³.
• On Windows, also install the Open Remote extension⁴.

Using VS Code instead of Positron:

• Add the REditorSupport extension⁵.
• Install the Python extension⁶.
• Add the {languageserver} R package to your projects as well (we’ll see how in the next chapter).

3.7.2 Emacs

For Emacs, configuration is minimal:

• Install the direnv package.
• Add python and ess for R support.

With this setup, opening a Nix-managed project automatically ensures Emacs uses the correct interpreter for that project (assuming we add an .envrc file to the project; more on this later).

---

1. https://mac.getutm.app/

2. https://apps.gnome.org/Boxes/

3. https://github.com/direnv/direnv-vscode

4. https://open-vsx.org/extension/kv9898/open-remote-wsl

5. https://marketplace.visualstudio.com/items?itemName=REditorSupport.r

6. https://marketplace.visualstudio.com/items?itemName=ms-python.python