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update NixOS VM tutorial

Browse source 
- clarify prerequisites
- update Nixpkgs release to 24.05
- remove the NixOS special cases, they are not needed
- rework a few side notes

Co-authored-by: wamirez <wamirez@protonmail.com>
This commit is contained in:
Valentin Gagarin 2024-08-31 19:38:41 +02:00
parent 873f9162ef
commit d879411922
1 changed files with 45 additions and 51 deletions
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96
source/tutorials/nixos/nixos-configuration-on-vm.md
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@ -13,7 +13,9 @@ Virtual machines are a practical tool for experimenting with or debugging NixOS
## What do you need? ## What do you need?
- A working [Nix installation](https://nix.dev/manual/nix/stable/installation/installation.html) on Linux, or [NixOS](https://nixos.org/manual/nixos/stable/index.html#sec-installation), with a graphical environment - A Linux system with virtualisation support
- (optional) A graphical environment for running a graphical virtual machine
- A working [Nix installation](https://nix.dev/manual/nix/stable/installation/installation.html)
- Basic knowledge of the [Nix language](reading-nix-language) - Basic knowledge of the [Nix language](reading-nix-language)
:::{important} :::{important}
@ -23,19 +25,15 @@ For a thorough treatment of the module system, check the [](module-system-deep-d
## Starting from a default NixOS configuration ## Starting from a default NixOS configuration
In this tutorial you will use a default configuration that is shipped with NixOS. :::{note}
You can also skip this section and copy the [sample configuration](sample-nixos-config) for this tutorial into a file `configuration.nix` in the current directory. You can also skip this section and copy the [sample configuration](sample-nixos-config) for this tutorial into a file `configuration.nix` in the current directory.
:::
::::{admonition} NixOS Use the `nixos-generate-config` command to create a configuration file that contains some useful defaults and configuration suggestions.
The configuration produced from the following setup also is used for the [NixOS minimal ISO image](https://nixos.org/download#nixos-iso):
On NixOS, use the `nixos-generate-config` command to create a configuration file that contains some useful defaults and configuration suggestions.
Beware that the result of this command depends on your current NixOS configuration.
The output of `nixos-generate-config` can be made reproducible in a `nix-shell` environment.
Here we provide a configuration that is used for the [NixOS minimal ISO image](https://nixos.org/download#nixos-iso):
```shell-session ```shell-session
nix-shell -I nixpkgs=channel:nixos-23.11 -p "$(cat <<EOF nix-shell -I nixpkgs=channel:nixos-24.05 -p "$(cat <<EOF
let let
pkgs = import <nixpkgs> { config = {}; overlays = []; }; pkgs = import <nixpkgs> { config = {}; overlays = []; };
iso-config = pkgs.path + /nixos/modules/installer/cd-dvd/installation-cd-minimal.nix; iso-config = pkgs.path + /nixos/modules/installer/cd-dvd/installation-cd-minimal.nix;
@ -45,27 +43,34 @@ EOF
)" )"
``` ```
It does the following: ::::{dropdown} Detailed explanation
- Provide Nixpkgs from a [channel](ref-pinning-nixpkgs)
- Take the configuration file for the minimal ISO image from the obtained version of the Nixpkgs repository This `nix-shell` invocation creates an environment based on Nixpkgs obtained from a [channel](ref-pinning-nixpkgs) and adds to it a derivation that is described by the Nix expression passed as a string to the `-p` option.
- Evaluate that NixOS configuration with `pkgs.nixos`
- Return the derivation which produces the `nixos-generate-config` executable from the evaluated configuration That Nix expression:
- Takes the configuration file for the minimal ISO image from the obtained version of Nixpkgs found in the lookup path `<nixpkgs>`
- Evaluates that NixOS configuration with `pkgs.nixos`
- Returns the derivation which produces the `nixos-generate-config` executable from the evaluated configuration
:::
By default, the generated configuration file is written to `/etc/nixos/configuration.nix`.
To avoid overwriting this file you have to specify the output directory.
Create a NixOS configuration in your working directory: Create a NixOS configuration in your working directory:
```shell-session ```shell-session
$ nixos-generate-config --dir ./ [nix-shell:~]$ nixos-generate-config --dir ./
``` ```
:::{note}
By default, when no `--dir` is specified, the generated configuration file is written to `/etc/nixos/configuration.nix`, which typically requires `sudo` permissions.
:::
In the working directory you will then find two files: In the working directory you will then find two files:
1. `hardware-configuration.nix` is specific to the hardware `nix-generate-config` is being run on. 1. `hardware-configuration.nix` is specific to the hardware `nix-generate-config` is being run on.
You can ignore that file for this tutorial because it has no effect inside a virtual machine. You can ignore that file for this tutorial because it has no effect inside a virtual machine.
2. `configuration.nix` contains various suggestions and comments for the initial setup of a desktop computer. 2. `configuration.nix` contains various suggestions and comments for the initial setup of a desktop computer.
::::
The default NixOS configuration without comments is: The default NixOS configuration without comments is:
@ -77,7 +82,7 @@ The default NixOS configuration without comments is:
boot.loader.systemd-boot.enable = true; boot.loader.systemd-boot.enable = true;
boot.loader.efi.canTouchEfiVariables = true; boot.loader.efi.canTouchEfiVariables = true;
system.stateVersion = "23.11"; system.stateVersion = "24.05";
} }
``` ```
@ -90,17 +95,8 @@ To be able to log in, add the following lines to the returned attribute set:
}; };
``` ```
We add two lightweight programs as an example: :::{note}
A configuration generated with `nixos-generate-config` contains this user configuration commented out.
```nix
environment.systemPackages = with pkgs; [
cowsay
lolcat
];
```
:::{admonition} NixOS
On NixOS your configuration generated with `nixos-generate-config` contains this user configuration commented out.
::: :::
Additionally, you need to specify a password for this user. Additionally, you need to specify a password for this user.
@ -110,6 +106,15 @@ For the purpose of demonstration only, you specify an insecure, plain text passw
initialPassword = "test"; initialPassword = "test";
``` ```
We add two lightweight programs as an example:
```nix
environment.systemPackages = with pkgs; [
cowsay
lolcat
];
```
:::{warning} :::{warning}
Do not use plain text passwords outside of this example unless you know what you are doing. See [`initialHashedPassword`](https://nixos.org/manual/nixos/stable/options.html#opt-users.extraUsers._name_.initialHashedPassword) or [`ssh.authorizedKeys`](https://nixos.org/manual/nixos/stable/options.html#opt-users.extraUsers._name_.openssh.authorizedKeys.keys) for more secure alternatives. Do not use plain text passwords outside of this example unless you know what you are doing. See [`initialHashedPassword`](https://nixos.org/manual/nixos/stable/options.html#opt-users.extraUsers._name_.initialHashedPassword) or [`ssh.authorizedKeys`](https://nixos.org/manual/nixos/stable/options.html#opt-users.extraUsers._name_.openssh.authorizedKeys.keys) for more secure alternatives.
::: :::
@ -143,7 +148,7 @@ The complete `configuration.nix` file looks like this:
lolcat lolcat
]; ];
system.stateVersion = "23.11"; system.stateVersion = "24.05";
} }
``` ```
@ -152,10 +157,10 @@ The complete `configuration.nix` file looks like this:
A NixOS virtual machine is created with the `nix-build` command: A NixOS virtual machine is created with the `nix-build` command:
```shell-session ```shell-session
$ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-23.11 -I nixos-config=./configuration.nix $ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-24.05 -I nixos-config=./configuration.nix
``` ```
This command builds the attribute `vm` from the `nixos-23.11` release of NixOS, using the NixOS configuration as specified in the relative path. This command builds the attribute `vm` from the `nixos-24.05` release of NixOS, using the NixOS configuration as specified in the relative path.
::::{dropdown} Detailed explanation ::::{dropdown} Detailed explanation
@ -173,16 +178,6 @@ This command builds the attribute `vm` from the `nixos-23.11` release of NixOS,
Here we set `nixpkgs` to refer to a [specific version of Nixpkgs](ref-pinning-nixpkgs) and set `nix-config` to the `configuration.nix` file in the current directory. Here we set `nixpkgs` to refer to a [specific version of Nixpkgs](ref-pinning-nixpkgs) and set `nix-config` to the `configuration.nix` file in the current directory.
:::{admonition} NixOS
On NixOS the `$NIX_PATH` environment variable is usually set up automatically, and there is also [a convenience command for building virtual machines](https://nixos.org/manual/nixos/stable/#sec-changing-config).
To use the current version of `nixpkgs` to build the virtual machine:
```shell-session
nixos-rebuild build-vm -I nixos-config=./configuration.nix
```
:::
::::
## Running the virtual machine ## Running the virtual machine
The previous command created a link with the name `result` in the working directory. The previous command created a link with the name `result` in the working directory.
@ -252,12 +247,12 @@ To create a virtual machine with a graphical user interface, add the following l
These three lines activate X11, the GDM display manager (to be able to login) and Gnome as desktop manager. These three lines activate X11, the GDM display manager (to be able to login) and Gnome as desktop manager.
::::{admonition} NixOS :::{tip}
On NixOS, use `installation-cd-graphical-gnome.nix` to generate the configuration file: You can also use the `installation-cd-graphical-gnome.nix` module to generate the configuration file from scratch:
```shell-session ```shell-session
nix-shell -I nixpkgs=channel:nixos-23.11 -p "$(cat <<EOF nix-shell -I nixpkgs=channel:nixos-24.05 -p "$(cat <<EOF
let let
pkgs = import <nixpkgs> { config = {}; overlays = []; }; pkgs = import <nixpkgs> { config = {}; overlays = []; };
iso-config = pkgs.path + /nixos/modules/installer/cd-dvd/installation-cd-graphical-gnome.nix; iso-config = pkgs.path + /nixos/modules/installer/cd-dvd/installation-cd-graphical-gnome.nix;
@ -292,14 +287,14 @@ The complete `configuration.nix` file looks like this:
initialPassword = "test"; initialPassword = "test";
}; };
system.stateVersion = "23.11"; system.stateVersion = "24.05";
} }
``` ```
To get graphical output, run the virtual machine without special options: To get graphical output, run the virtual machine without special options:
```shell-session ```shell-session
$ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-23.11 -I nixos-config=./configuration.nix $ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-24.05 -I nixos-config=./configuration.nix
$ ./result/bin/run-nixos-vm $ ./result/bin/run-nixos-vm
``` ```
@ -347,7 +342,7 @@ Arguments to QEMU can also be added to the configuration file:
initialPassword = "test"; initialPassword = "test";
}; };
system.stateVersion = "23.11"; system.stateVersion = "24.05";
} }
``` ```
@ -365,7 +360,6 @@ The NixOS manual has chapters on [X11](https://nixos.org/manual/nixos/stable/#se
- [NixOS source code: `vm` attribute in `default.nix`](https://github.com/NixOS/nixpkgs/blob/master/nixos/default.nix). - [NixOS source code: `vm` attribute in `default.nix`](https://github.com/NixOS/nixpkgs/blob/master/nixos/default.nix).
- [Nix manual: `nix-build`](https://nix.dev/manual/nix/stable/command-ref/nix-build.html). - [Nix manual: `nix-build`](https://nix.dev/manual/nix/stable/command-ref/nix-build.html).
- [Nix manual: common command-line options](https://nix.dev/manual/nix/stable/command-ref/opt-common.html). - [Nix manual: common command-line options](https://nix.dev/manual/nix/stable/command-ref/opt-common.html).
- [Nix manual: `NIX_PATH` environment variable](https://nix.dev/manual/nix/stable/command-ref/env-common.html#env-NIX_PATH).
- [QEMU User Documentation](https://www.qemu.org/docs/master/system/qemu-manpage.html) for more runtime options - [QEMU User Documentation](https://www.qemu.org/docs/master/system/qemu-manpage.html) for more runtime options
- [NixOS option search: `virtualisation.qemu`](https://search.nixos.org/options?query=virtualisation.qemu) for declarative virtual machine configuration - [NixOS option search: `virtualisation.qemu`](https://search.nixos.org/options?query=virtualisation.qemu) for declarative virtual machine configuration