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How to hack on Nix and try your changes

Written by Solène, on 19 August 2022.
Tags: #nix #development #nixos

Comments on Fediverse/Mastodon

1. Introduction §

Not obvious development process is hard to document. I wanted to make changes to the nix program, but I didn't know how to try them.

Fortunately, a coworker explained to me the process, and here it is!

The nix project GitHub page

2. Get the sources and compile §

First, you need to get the sources of the project, and compile it in some way to run it from the project directory:

git clone https://github.com/NixOS/nix/
cd nix
./configure --prefix=$PWD

3. Run the nix daemon §

In order to try nix, we need to stop nix-daemon.service, but also stop nix-daemon.socket to prevent it to restart the nix-daemon.

systemctl stop nix-daemon.socket
systemctl stop nix-daemon.service

Now, when you want your nix-daemon to work, just run this command from the project directory:

sudo bin/nix --extra-experimental-features nix-command daemon

Note this command doesn't fork on background.

If you need some settings in the nix.conf file, you have to create etc/nix/nix.conf relative to the project directory.

4. Restart the nix-daemon §

Once you are done with the development, exit your running daemon and restart the service and socket.

systemctl start nix-daemon.socket
systemctl start nix-daemon.service