As I mentioned earlier, NixOS can only manage system-level configuration. To manage user-level configuration in the Home directory, we need to install Home Manager.
According to the official [Home Manager Manual](https://nix-community.github.io/home-manager/index.xhtml), to install Home Manager as a module of NixOS, we first need to create `/etc/nixos/home.nix`. Here's an example of its contents:
After adding `/etc/nixos/home.nix`, you need to import this new configuration file in `/etc/nixos/flake.nix` to make use of it, use the following command to generate an example in the current folder for reference:
```shell
nix flake new example -t github:nix-community/home-manager#nixos
```
After adjusting the parameters, the content of `/etc/nixos/flake.nix` is as follows:
> If your system's hostname is not `nixos-test`, you need to modify the name of `nixosConfigurations` in `flake.nix`, or use `--flake /etc/nixos#nixos-test` to specify the configuration name.
After the installation, all user-level packages and configuration can be managed through `/etc/nixos/home.nix`. When running `sudo nixos-rebuild switch`, the configuration of home-manager will be applied automatically. (**It's not necessary to run `home-manager switch` manually**!)
To find the options we can use in `home.nix`, referring to the following documents:
- [Home Manager - Appendix A. Configuration Options](https://nix-community.github.io/home-manager/options.html): A list of all options, it is recommended to search for keywords in it.
- [home-manager](https://github.com/nix-community/home-manager): Some options are not listed in the official documentation, or the documentation is not clear enough, you can directly search and read the corresponding source code in this home-manager repo.
When it comes to managing software packages and configurations, you often have the choice of using either NixOS modules (`configuration.nix`) or Home Manager (`home.nix`). This poses a dilemma: **What are the differences between putting packages or configuration in NixOS modules vs Home Manager modules, and how should you decide?**
First, let's understand the differences. Packages and configuration installed through NixOS modules are global to the entire system. Global configurations are typically stored in `/etc`, and globally installed packages are linked accordingly. Regardless of the user you switch to, you can access and use these packages and configurations.
On the other hand, everything installed through Home Manager is specific to the corresponding user. Once you switch to another user, those configurations and packages become unavailable.
Based on these characteristics, here is a general recommended approach:
- NixOS modules: Install core system components and other software packages/configurations required by all users.
- For example, if you want a package to be accessible even when you switch to the root user, or if you want a configuration to take effect globally on the system, you should install it through a NixOS module.
## How to use packages installed by Home Manager with privileged access?
The first thing that comes to mind is to switch to `root`, but then any packages installed by the current user through `home.nix` will be unavailable.
let's take `kubectl` as an example(it's pre-installed via `home.nix`):
```sh
# 1. kubectl is available
› kubectl | head
kubectl controls the Kubernetes cluster manager.
Find more information at: https://kubernetes.io/docs/reference/kubectl/
......
# 2. switch user to `root`
› sudo su
# 3. kubectl is no longer available
> kubectl
Error: nu::shell::external_command
× External command failed
╭─[entry #1:1:1]
1 │ kubectl
· ───┬───
· ╰── executable was not found
╰────
help: No such file or directory (os error 2)
/home/ryan/nix-config> exit
```
But it's possible to run those packages with privileged access without switching to `root`, by using `sudo`, we temporarily grant the current user privileged access to system resources:
