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75 lines
4.1 KiB
Markdown
75 lines
4.1 KiB
Markdown
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After learning the basics of the Nix language, we can start using it to configure our NixOS. The default configuration for NixOS is located at `/etc/nixos/configuration.nix`, which contains all the declarative configuration for the system, such as time zone, language, keyboard layout, network, users, file system, boot options, etc.
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If we want to modify the system state in a reproducible way (**which is also the most recommended way**), we need to manually edit `/etc/nixos/configuration.nix`, and then execute `sudo nixos-rebuild switch` to apply the modified configuration, it will generate a new system environment based on the configuration file we modified, sets the new environment as the default one, and also preserves & added the previous environment into the boot options of grub/sytemd-boot. This ensures we can always roll back to the old environment(even if the new environment fails to start).
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`/etc/nixos/configuration.nix` is the classic method to configure NixOS, which relies on data sources configured by `nix-channel` and has no version-locking mechanism, making it difficult to ensure the reproducibility of the system. **A better approach is to use Flakes**, which can ensure the reproducibility of the system and make it easy to manage the configuration.
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Now first, let's learn how to manage NixOS through the classic method, `/etc/nixos/configuration.nix`, and then migrate to the more advanced Flakes.
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## Configuring the system using `/etc/nixos/configuration.nix`
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As I mentioned earlier, this is the classic method to configured NixOS, and also the default method currently used by NixOS. It relies on data sources configured by `nix-channel` and has no version-locking mechanism, making it difficult to ensure the reproducibility of the system.
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For example, to enable ssh and add a user "ryan", simply add the following content into `/etc/nixos/configuration.nix`:
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```nix
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# Edit this configuration file to define what should be installed on
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# your system. Help is available in the configuration.nix(5) man page
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# and in the NixOS manual (accessible by running 'nixos-help').
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{ config, pkgs, ... }:
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{
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imports =
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[ # Include the results of the hardware scan.
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./hardware-configuration.nix
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];
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# Omit the previous configuration.......
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# add user ryan
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users.users.ryan = {
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isNormalUser = true;
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description = "ryan";
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extraGroups = [ "networkmanager" "wheel" ];
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openssh.authorizedKeys.keys = [
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# replace with your own public key
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"ssh-ed25519 <some-public-key> ryan@ryan-pc"
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];
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packages = with pkgs; [
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firefox
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# thunderbird
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];
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};
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# enable openssh-server
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services.openssh = {
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enable = true;
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permitRootLogin = "no"; # disable root login
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passwordAuthentication = false; # disable password login
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openFirewall = true;
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forwardX11 = true; # enable X11 forwarding
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};
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# omit the rest of the configuration.......
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}
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```
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In this configuration, we declared that we want to enable the openssh service, add an ssh public key for the user ryan, and disable password login.
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Now, let's run `sudo nixos-rebuild switch` to deploy the modified configuration, and then we can login to the system using ssh with the ssh keys we configured.
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Any reproducible changes to the system can be made by modifying `/etc/nixos/configuration.nix` and deploying the changes by running `sudo nixos-rebuild switch`.
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All configuration options in `/etc/nixos/configuration.nix` can be found in the following places:
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- By searching on Google, such as `Chrome NixOS`, which will provide NixOS informations related to Chrome. Generally, the NixOS Wiki and the source code of Nixpkgs will be among the top results.
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- By searching for keywords in [NixOS Options Search](https://search.nixos.org/options).
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- For system-level configuration, relevant documentation can be found in [Configuration - NixOS Manual](https://nixos.org/manual/nixos/unstable/index.html#ch-configuration).
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- By searching for keywords directly in the source code of [nixpkgs](https://github.com/NixOS/nixpkgs) on GitHub.
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## References
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- [Overview of the NixOS Linux distribution]( https://nixos.wiki/wiki/Overview_of_the_NixOS_Linux_distribution)
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