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https://github.com/NixOS/nix.dev.git
synced 2024-10-18 14:32:43 -04:00
update NixOS VM tutorial
- 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
parent
873f9162ef
commit
d879411922
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@ -13,7 +13,9 @@ Virtual machines are a practical tool for experimenting with or debugging NixOS
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## What do you need?
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- 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
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- A Linux system with virtualisation support
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- (optional) A graphical environment for running a graphical virtual machine
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- A working [Nix installation](https://nix.dev/manual/nix/stable/installation/installation.html)
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- Basic knowledge of the [Nix language](reading-nix-language)
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:::{important}
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@ -23,19 +25,15 @@ For a thorough treatment of the module system, check the [](module-system-deep-d
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## Starting from a default NixOS configuration
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In this tutorial you will use a default configuration that is shipped with NixOS.
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:::{note}
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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.
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:::
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::::{admonition} NixOS
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On NixOS, use the `nixos-generate-config` command to create a configuration file that contains some useful defaults and configuration suggestions.
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Beware that the result of this command depends on your current NixOS configuration.
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The output of `nixos-generate-config` can be made reproducible in a `nix-shell` environment.
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Here we provide a configuration that is used for the [NixOS minimal ISO image](https://nixos.org/download#nixos-iso):
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Use the `nixos-generate-config` command to create a configuration file that contains some useful defaults and configuration suggestions.
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The configuration produced from the following setup also is used for the [NixOS minimal ISO image](https://nixos.org/download#nixos-iso):
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```shell-session
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nix-shell -I nixpkgs=channel:nixos-23.11 -p "$(cat <<EOF
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nix-shell -I nixpkgs=channel:nixos-24.05 -p "$(cat <<EOF
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let
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pkgs = import <nixpkgs> { config = {}; overlays = []; };
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iso-config = pkgs.path + /nixos/modules/installer/cd-dvd/installation-cd-minimal.nix;
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@ -45,27 +43,34 @@ EOF
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)"
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```
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It does the following:
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- Provide Nixpkgs from a [channel](ref-pinning-nixpkgs)
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- Take the configuration file for the minimal ISO image from the obtained version of the Nixpkgs repository
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- Evaluate that NixOS configuration with `pkgs.nixos`
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- Return the derivation which produces the `nixos-generate-config` executable from the evaluated configuration
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::::{dropdown} Detailed explanation
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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.
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That Nix expression:
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- Takes the configuration file for the minimal ISO image from the obtained version of Nixpkgs found in the lookup path `<nixpkgs>`
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- Evaluates that NixOS configuration with `pkgs.nixos`
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- Returns the derivation which produces the `nixos-generate-config` executable from the evaluated configuration
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:::
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By default, the generated configuration file is written to `/etc/nixos/configuration.nix`.
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To avoid overwriting this file you have to specify the output directory.
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Create a NixOS configuration in your working directory:
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```shell-session
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$ nixos-generate-config --dir ./
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[nix-shell:~]$ nixos-generate-config --dir ./
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```
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:::{note}
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By default, when no `--dir` is specified, the generated configuration file is written to `/etc/nixos/configuration.nix`, which typically requires `sudo` permissions.
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:::
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In the working directory you will then find two files:
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1. `hardware-configuration.nix` is specific to the hardware `nix-generate-config` is being run on.
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You can ignore that file for this tutorial because it has no effect inside a virtual machine.
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2. `configuration.nix` contains various suggestions and comments for the initial setup of a desktop computer.
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::::
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The default NixOS configuration without comments is:
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@ -77,7 +82,7 @@ The default NixOS configuration without comments is:
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boot.loader.systemd-boot.enable = true;
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boot.loader.efi.canTouchEfiVariables = true;
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system.stateVersion = "23.11";
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system.stateVersion = "24.05";
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}
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```
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@ -90,6 +95,17 @@ To be able to log in, add the following lines to the returned attribute set:
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};
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```
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:::{note}
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A configuration generated with `nixos-generate-config` contains this user configuration commented out.
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:::
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Additionally, you need to specify a password for this user.
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For the purpose of demonstration only, you specify an insecure, plain text password by adding the `initialPassword` option to the user configuration:
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```nix
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initialPassword = "test";
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```
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We add two lightweight programs as an example:
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```nix
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@ -99,17 +115,6 @@ We add two lightweight programs as an example:
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];
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```
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:::{admonition} NixOS
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On NixOS your configuration generated with `nixos-generate-config` contains this user configuration commented out.
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:::
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Additionally, you need to specify a password for this user.
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For the purpose of demonstration only, you specify an insecure, plain text password by adding the `initialPassword` option to the user configuration:
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```nix
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initialPassword = "test";
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```
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:::{warning}
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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.
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:::
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@ -143,7 +148,7 @@ The complete `configuration.nix` file looks like this:
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lolcat
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];
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system.stateVersion = "23.11";
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system.stateVersion = "24.05";
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}
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```
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@ -152,10 +157,10 @@ The complete `configuration.nix` file looks like this:
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A NixOS virtual machine is created with the `nix-build` command:
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```shell-session
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$ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-23.11 -I nixos-config=./configuration.nix
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$ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-24.05 -I nixos-config=./configuration.nix
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```
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This command builds the attribute `vm` from the `nixos-23.11` release of NixOS, using the NixOS configuration as specified in the relative path.
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This command builds the attribute `vm` from the `nixos-24.05` release of NixOS, using the NixOS configuration as specified in the relative path.
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::::{dropdown} Detailed explanation
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@ -173,16 +178,6 @@ This command builds the attribute `vm` from the `nixos-23.11` release of NixOS,
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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.
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:::{admonition} NixOS
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On NixOS the `$NIX_PATH` environment variable is usually set up automatically, and there is also [a convenience command for building virtual machines](https://nixos.org/manual/nixos/stable/#sec-changing-config).
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To use the current version of `nixpkgs` to build the virtual machine:
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```shell-session
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nixos-rebuild build-vm -I nixos-config=./configuration.nix
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```
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:::
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::::
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## Running the virtual machine
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The previous command created a link with the name `result` in the working directory.
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@ -252,12 +247,12 @@ To create a virtual machine with a graphical user interface, add the following l
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These three lines activate X11, the GDM display manager (to be able to login) and Gnome as desktop manager.
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::::{admonition} NixOS
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:::{tip}
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On NixOS, use `installation-cd-graphical-gnome.nix` to generate the configuration file:
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You can also use the `installation-cd-graphical-gnome.nix` module to generate the configuration file from scratch:
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```shell-session
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nix-shell -I nixpkgs=channel:nixos-23.11 -p "$(cat <<EOF
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nix-shell -I nixpkgs=channel:nixos-24.05 -p "$(cat <<EOF
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let
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pkgs = import <nixpkgs> { config = {}; overlays = []; };
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iso-config = pkgs.path + /nixos/modules/installer/cd-dvd/installation-cd-graphical-gnome.nix;
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@ -292,14 +287,14 @@ The complete `configuration.nix` file looks like this:
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initialPassword = "test";
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};
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system.stateVersion = "23.11";
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system.stateVersion = "24.05";
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}
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```
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To get graphical output, run the virtual machine without special options:
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```shell-session
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$ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-23.11 -I nixos-config=./configuration.nix
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$ nix-build '<nixpkgs/nixos>' -A vm -I nixpkgs=channel:nixos-24.05 -I nixos-config=./configuration.nix
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$ ./result/bin/run-nixos-vm
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```
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@ -347,7 +342,7 @@ Arguments to QEMU can also be added to the configuration file:
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initialPassword = "test";
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};
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system.stateVersion = "23.11";
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system.stateVersion = "24.05";
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}
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```
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@ -365,7 +360,6 @@ The NixOS manual has chapters on [X11](https://nixos.org/manual/nixos/stable/#se
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- [NixOS source code: `vm` attribute in `default.nix`](https://github.com/NixOS/nixpkgs/blob/master/nixos/default.nix).
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- [Nix manual: `nix-build`](https://nix.dev/manual/nix/stable/command-ref/nix-build.html).
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- [Nix manual: common command-line options](https://nix.dev/manual/nix/stable/command-ref/opt-common.html).
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- [Nix manual: `NIX_PATH` environment variable](https://nix.dev/manual/nix/stable/command-ref/env-common.html#env-NIX_PATH).
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- [QEMU User Documentation](https://www.qemu.org/docs/master/system/qemu-manpage.html) for more runtime options
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- [NixOS option search: `virtualisation.qemu`](https://search.nixos.org/options?query=virtualisation.qemu) for declarative virtual machine configuration
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