Nix configuration

Inspired by Dustin Lyons' repo.

Lets you have 99% the same command-line tools and configuration across macOS, Linux (nixOS) and Windows (WSL).

See Screenshots for some pictures.

Bootstrapping

You need to do this only once for a new machine.

macOS

1. Install Nix using the Determinate Systems Nix installer.

2. Install Homebrew (it's only used to install Casks and Mac App Store apps, its not in the $PATH).

3. Ensure that the current user is able to clone the private secrets repo before proceeding to the next step, by putting the SSH private key needed to clone the repo into $HOME/.ssh/id_rsa.

4. Run env FLAKE=<NAME> ./bootstrap. After a successful bootstrap, the hostname will be updated to match the flake.

5. Whenever you make configuration changes, run ./rebuild. If any files are reported as being in the way, move them out of the way and re-run.

WSL

1. Install and start up NixOS following the instructions in the NixOS-WSL repository.

2. Run sudo nix-channel --update and sudo nixos-rebuild switch to set up the base system.

3. Run the below to enter a shell with git installed:

   export NIXPKGS_ALLOW_UNFREE=1
   nix-shell --impure -p git

4. Clone this repository to /etc/nixos/nixos-config.

5. Ensure the root user has the SSH public key for cloning the secret repository referenced by the flake.nix, it should be put in /root/.ssh with appropriate permissions. Run ssh git@github.com at least once, and save the GitHub SSH key (needed to avoid the nixos-install command hanging waiting for user input when cloning the secrets repo).

6. Change to /etc/nixos/nixos-config and run env FLAKE=<NAME> ./rebuild to do the initial build. Subsequent builds will not need you to specify the hostname.

7. To change the default user from being root (after failing to use nixos), run:

   sudo -E /run/current-system/sw/bin/nixos-rebuild boot --impure --flake .#<NAME>

   Do not run ./rebuild or nixos-rebuild switch after this!

8. Then exit the NixOS shell, and run wsl -t NixOS to stop it from running.

9. Run wsl -d NixOS --user root exit.

10. Stop the distribution again with wsl -t NixOS. Now when you next start it, it will use the user created by the flake.

NixOS

1. Download the latest NixOS stable distribution, these instructions were tested with 24.05. Download the minimal distribution, not graphical.

2. Create a bootable USB.

3. Boot from the USB device.

4. Create root and boot partitions and format them with the file system of your choice, use the nixos and swap labels, as our configuration depends on these labels, and mount the file systems in /mnt and /mnt/boot, respectively.

5. Run nixos-generate-config --root /mnt, and copy the generated /etc/nixos/*.nix files to $HOME.

6. Remove /etc/nixos directory entirely.

7. Clone this repository to /mnt/etc/nixos:

   export NIXPKGS_ALLOW_UNFREE=1
   nix-shell --impure -p git
   git clone https://github.com/leonbreedt/nix-config.git /mnt/etc/nixos

8. Move the generated $HOME/hardware-configuration.nix file to the hw subdirectory of /mnt/etc/nixos if not already there, and name it after the machine host name.

   Remember, this file contains the details of the partitions specific to this machine, as well as required kernel modules, which will be needed to rebuild the system while its hardware remains the same.

   Edit it if needed. Uncomment the explicit per-interface enablement for the interfaces you want to use DHCP.

   mv $HOME/hardware-configuration.nix /mnt/etc/nixos/hw/<HOSTNAME>.nix

9. Ensure the root user has the SSH public key for cloning the secret repository referenced by the flake.nix, it should be put in /root/.ssh with appropriate permissions. Run ssh git@github.com at least once, and save the GitHub SSH key (needed to avoid the nixos-install command hanging waiting for user input when cloning the secrets repo).

10. Create a script named /root/git-askpass.sh and put the below in it:

    echo PASSWORD

    Where PASSWORD is the passworf for the GitHub user. Make it executable with chmod +x /root/git-askpass.sh.

11. Run export GIT_ASKPASS=/root/git-askpass.sh

12. Run the installer in flake installation mode, where <SYSTEM> is the name of the system in flake.nix:

    nixos-install -v --impure --flake "/mnt/etc/nixos#<SYSTEM>"

    You will be prompted for a root password, which you can use after reboot to give the normal user a password to log in if you want to use X11. Only the normal user will be able to SSH in.

    Now you have a purely flake-based NixOS installation.

13. Whenever you make changes to the configuration, you can Run env FLAKE=<SYSTEM> ./rebuild in /etc/nixos, where <SYSTEM> is the name of the system in flake.nix. This will run nixos-rebuild in flake mode, and switch to the built configuration afterwards.

Using

Whenever you make changes to the configuration, just run ./rebuild in the cloned flake directory to apply it to your system. Since the value of FLAKE defaults to the current hostname, you don't have to pass a hostname for subsequent builds, once it has been built once.

Troubleshooting

There are still some rough edges with this configuration. Mainly around first-time setup/retrieval of credentials from my private repo, you won't get access to it :)

If you remove the private repo input in flake.nix and the secrets references you can likely get it going.

Missing commands do not print derivations that resolve it

If you run a command that is not installed, and you get an error like this:

DBI connect('dbname=/nix/var/nix/profiles/per-user/root/channels/nixos/programs.sqlite','',...) failed:
unable to open database file at /run/current-system/sw/bin/command-not-found line 13.

Then you can likely resolve it by updating your Nix channels for the root user.

sudo nix-channel --update

Rust completion doesn't work in VIM

Since are using rustup instead of global native Nix Rust packages, make sure rust-analyzer is installed:

rustup component add rust-analyzer

Screenshots

macOS

Linux

WSL