# FAQ
This is more meant as a "Fully Anticipated Questions" than a "Frequently Asked Questions", as they're anticipated as common pitfalls to using NDE.

## OK, I put your snippets into my NixOS configuration, and I put my Doom Emacs configuration as well. How do I `doom sync`?

To update your Doom Emacs config, you simply run `nixos-rebuild switch` (or `home-manager switch` if you use Home-Manager standalone). Nix-Doom-Emacs will do everything else for you.

## How do I install my favourite package?

You should use the `emacsPackagesOverlay` attribute. Here's an example that installs `magit-delta` which depends on Git:

```nix
programs.doom-emacs = {
  # ...
  emacsPackagesOverlay = self: super: {
    magit-delta = super.magit-delta.overrideAttrs (esuper: {
      buildInputs = esuper.buildInputs ++ [ pkgs.git ];
    });
  }
};
```

### But what if my package is from a Git source, and isn't on ELPA?

This requires a few more lines, but it isn't by any means difficult. For an example, this installs `idris2-mode` which isn't on ELPA, but is hosted on GitHub:

```nix
programs.doom-emacs = {
  # ...
  emacsPackagesOverlay = self: super: {
    idris2-mode = self.trivialBuild {
      pname = "idris2-mode";
      ename = "idris2-mode";
      version = "0.0.0";
      buildInputs = [ self.prop-menu ];
      src = pkgs.fetchFromGitHub {
        owner = "idris-community";
        repo = "idris2-mode";
        rev = "4a3f9cdb1a155da59824e39f0ac78ccf72f2ca97";
        sha256 = "sha256-TxsGaG2fBRWWP9aas59kiNnUVD4ZdNlwwaFbM4+n81c=";
      };
    };
  }
};
```

### Help! My favourite package doesn't work after adding it in!

This usually happens when the package depends on either some ELPA package or a normal package that you need to add into the `buildInputs` to make it work. 
Let's take the above `idris2-mode` package, and I'll remove the `buildInputs` line:

**WARNING**: THIS IS ERRONEOUS CODE FOR DEMONSTRATION. DO NOT USE THIS SNIPPET, THE ABOVE ONE IS THE FUNCTIONING VERSION.
```nix
programs.doom-emacs = {
  # ...
  emacsPackagesOverlay = self: super: {
    idris2-mode = self.trivialBuild {
      pname = "idris2-mode";
      ename = "idris2-mode";
      version = "0.0.0";
      src = pkgs.fetchFromGitHub {
        owner = "idris-community";
        repo = "idris2-mode";
        rev = "4a3f9cdb1a155da59824e39f0ac78ccf72f2ca97";
        sha256 = "sha256-TxsGaG2fBRWWP9aas59kiNnUVD4ZdNlwwaFbM4+n81c=";
      };
    };
  }
};
```

This will error with (this is a part of the build log):

```
In toplevel form:
idris2-hole-list.el:27:2: Error: Cannot open load file: No such file or directory, prop-menu

In toplevel form:
idris2-info.el:29:2: Error: Cannot open load file: No such file or directory, prop-menu

In idris2-ipkg-pkgs-flags-for-current-buffer:
idris2-ipkg-mode.el:372:2: Warning: docstring wider than 80 characters

In toplevel form:
idris2-mode.el:20:2: Error: Cannot open load file: No such file or directory, prop-menu

In idris2-prover-end:
idris2-prover.el:378:2: Warning: docstring wider than 80 characters

In toplevel form:
idris2-repl.el:29:2: Error: Cannot open load file: No such file or directory, prop-menu
```

The way to fix it is by just adding the dependency it's complaining about.

## How do I enable the service?

There aren't many complications about this. If you use the Home-Manager module, it's simply `services.emacs.enable = true;`. The Home-Manager module will do the rest for you.

But if you're not, and you're using a standalone method, you'll need:

```nix
services.emacs = {
  enable = true;
  package = inputs.doom-emacs.packages.${system}.doom-emacs;
};
```

You can now run `emacsclient -c` to connect to the daemon.

## What is `trivialBuild`?

Though beyond the scope of this document, `trivialBuild` is a Nixpkgs function to trivially build Emacs packages. You can use it to build e.g. local packages or packages hosted on Git repositories. It is not a Nix-Doom-Emacs tool.

## Help! Nix-Doom-Emacs isn't working if I set DOOMDIR or EMACSDIR

You shouldn't do that. The only thing that Nix-Doom-Emacs writes in your $HOME is `~/.emacs.d/init.el`, which points to the Nix store. Make sure to remove them from your configuration, then reboot after rebuilding it. If for just the session, you can just `unset` those 2 variables.

# Help! on MacOS, it says "Too many files open"!

Running `ulimit -S -n 2048` will fix it for the duration of your shell session.