#### TL;DR 1. Connect both NixOS systems to the same network. 2. On the host system, run: `nix run github:edolstra/nix-serve` 3. Use SSH port forwarding: `ssh -L 5000:127.0.0.1:5000 @ -N` 4. Build with: `sudo nix build .#nixosConfigurations..config.system.build.toplevel --extra-substituters 'http://localhost:5000' --no-require-sigs` 5. Switch configuration: `sudo nixos-rebuild switch --flake .#` ### Introduction In NixOS, rebuilding and redownloading packages can be time-consuming. To streamline this process, you can use another NixOS system on your home network as a binary cache. This guide will walk you through setting up a binary cache on a host machine and configuring another system to use this cache, reducing rebuild and download times for Nix flakes configurations. ### Step-by-Step Instructions #### Step 1: Connect Both Systems to the Same Network Ensure both the host and target NixOS systems are connected to the same LAN or Wi-Fi network. This setup is essential for seamless communication between the systems. #### Step 2: Run `nix-serve` on the Host Machine On the host machine, open a terminal and run the following command: ```sh nix run github:edolstra/nix-serve ``` This command launches the `nix-serve` utility, turning your host system into a binary cache server. #### Step 3: Set Up SSH Port Forwarding To avoid signature verification issues, use SSH port forwarding. Open a terminal on the target system and run: ```sh ssh -L 5000:127.0.0.1:5000 @ -N ``` Replace `` with your username and `` with the IP address of the host machine. This command forwards port 5000 on the target system to port 5000 on the host system. #### Step 4: Build the System Using `nix build` Since `nixos-rebuild` doesn't support specifying substituters directly, use `nix build`: ```sh sudo nix build .#nixosConfigurations..config.system.build.toplevel --extra-substituters 'http://localhost:5000' --no-require-sigs ``` Replace `` with the name of your NixOS configuration. This command builds the system using the binary cache on the host machine. #### Step 5: Switch to the New Configuration After building the system, switch to the new configuration using `nixos-rebuild`: ```sh sudo nixos-rebuild switch --flake .# ``` Replace `` with the appropriate configuration name. ### Conclusion By following these steps, you can effectively use another NixOS system as a binary cache on your home network, saving time on package rebuilds and downloads. This setup is particularly useful for users working with Nix flakes, enabling a more efficient and streamlined NixOS experience.

ehsan2003

Using Another NixOS System as a Binary Cache for Flake Configurations on Your Home Network

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