NixOS:nixos-rebuild build-vm - Revision history

TornaxO7: fix sectioning

2025-09-24T09:57:43Z

fix sectioning

← Older revision		Revision as of 09:57, 24 September 2025
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	</syntaxhighlight>		</syntaxhighlight>

	== Troubleshooting ==		= Troubleshooting =
	=== Still can't login after updating configuration ===		== Still can't login after updating configuration ==
	When running a virtual machine a file called <code>$hostname.qcow2</code> is created in your current working directory. After changing your <code>/etc/nixos/configuration.nix</code> delete this file, rebuild and then start the new virtual machine. Now you should be able to login.		When running a virtual machine a file called <code>$hostname.qcow2</code> is created in your current working directory. After changing your <code>/etc/nixos/configuration.nix</code> delete this file, rebuild and then start the new virtual machine. Now you should be able to login.

	== Networking ==		= Networking =

	=== qemu ===		== qemu ==

	To enable connecting from your host to your virtual machine, you'll need to forcefully override the default networking settings to apply those from https://wiki.qemu.org/Documentation/Networking#How_to_get_SSH_access_to_a_guest instead. For example, to expose the VM's port 80 on the (unprivileged) port 8009 of the 'localhost' of the host:		To enable connecting from your host to your virtual machine, you'll need to forcefully override the default networking settings to apply those from https://wiki.qemu.org/Documentation/Networking#How_to_get_SSH_access_to_a_guest instead. For example, to expose the VM's port 80 on the (unprivileged) port 8009 of the 'localhost' of the host:
Line 93:		Line 93:
	</syntaxhighlight>		</syntaxhighlight>

	== Alternatives ==		= Alternatives =

	=== Bootable ISO ===		== Bootable ISO ==
	Build it as a [https://nix.dev/tutorials/nixos/building-bootable-iso-image bootable ISO image]:		Build it as a [https://nix.dev/tutorials/nixos/building-bootable-iso-image bootable ISO image]:

	=== VM ===		== VM ==
	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">
	{		{

TornaxO7: Restructured page, add more text more sections

2025-09-24T09:53:11Z

Restructured page, add more text more sections

← Older revision		Revision as of 09:53, 24 September 2025
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	~~A virtual machine can be created , it will use your /etc/nixos/configuration.nix to make a 'clone' of your system. Useful for testing new configurations.~~		The commands

	<code>		* <code>nixos-rebuild build-vm</code>
	nixos-rebuild build-vm		* <code>nixos-rebuild build-vm-with-bootloader</code>

			will build a virtual machine running NixOS with your system's configuration (usually <code>/etc/nixos/configuration.nix</code>) by using [[Qemu]].

			One of its usages is for testing new configurations without needing to try them on the host.

	~~nixos-rebuild build-vm -I nixos-config~~=~~./configuration.nix -I nix_path~~=~~'<nixpkgs/nixos>' --max-jobs 4 --show-trace # e.g. to specify the environment variables / cores used~~		= Usage =
	~~</code>~~

	You can also use <code>build-vm-with-bootloader</code>. From the man page: this boots using the regular boot loader of your configuration rather than booting directly into the kernel and initial ramdisk of the system.		== Create login user ==

	~~You~~ will ~~not be able~~ to login to ~~this virtual machine, as the~~ passwords are not carried over to the virtual machine ~~you build~~.		Before calling one of the commands above, you will have to create a user with an initial password first which you can login to because your passwords of your current system are not carried over to the virtual machine.

	~~You should have~~ user ~~nixosvmtest (isSystemUser or isNormalUser)~~		Here is an example for a default user which you can simply add to your system config:
	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">
	users.users.nixosvmtest.isSystemUser = true ;		users.users.nixosvmtest.isSystemUser = true;
	users.users.nixosvmtest.initialPassword = "test";		users.users.nixosvmtest.initialPassword = "test";

			users.groups.nixosvmtest = {};
			users.users.nixosvmtest.group = "nixosvmtest";
	</syntaxhighlight>		</syntaxhighlight>

	If you ~~have a user called nixosvmtest for example,~~ you can ~~add~~		See this [https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2 discourse-answer] for more information.

			== Create and run virtual machine ==
			Create the virtual machine by using of the commands above. Afterwards you will find an executable file in <code>./result/bin</code>. By executing the file qemu will open up and you can start testing the system.

	~~<syntaxhighlight lang~~=~~"nix">~~		== Examples ==
	~~users.users.nixosvmtest.group~~ = ~~"nixosvmtest";~~
	~~users.groups.nixosvmtest~~ = ~~{};~~
	~~</syntaxhighlight>~~

	~~to your~~ <~~code~~>~~/etc/~~nixos~~/configuration.nix</code>~~		<syntaxhighlight lang="bash">
			# build vm of your system config
			nixos-rebuild build-vm

	~~you should now be able~~ to ~~login and test your system with this user and password~~.		# e.g. to specify the environment variables / cores used
			nixos-rebuild build-vm\
			-I nixos-config=./configuration.nix\
			-I nix_path='<nixpkgs/nixos>'\
			--max-jobs 4\
			--show-trace

	~~https~~:~~//discourse~~.nixos~~.org/t/default~~-~~login~~-~~and~~-~~password~~-~~for-nixos/4683~~/2		# From the man page: This boots using the regular boot loader of your configuration
			# rather than booting directly into the kernel and initial ramdisk of the system.
			nixos-rebuild build-vm-with-bootloader
			</syntaxhighlight>

	== Configure Virtual Machine ==		= Configure Virtual Machine =

	By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can ~~set~~ options ~~<code>~~virtualisation.vmVariant.virtualisation.~~cores~~</code> ~~and~~ <code>virtualisation.vmVariant.virtualisation.~~memorySize~~</code> to ~~enlarge the CPU cores and memory size for the virtual machine.~~		By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with a desktop environment enabled inside. You can configure the allocated resources with either
			* [https://search.nixos.org/options?channel=25.05&show=virtualisation.vmVariant&query=virtualisation.vmVariant <code>virtualisation.vmVariant</code>]
			* [https://search.nixos.org/options?channel=25.05&show=virtualisation.vmVariantWithBootLoader&query=virtualisation.vmVariant <code>virtualisation.vmVariantWithBootloader</code>]
			by adding the following to your config:

	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">
	{		# replace `vmVariant` with `vmVariantWithBootLoader` if you are going to use `build-vm-with-bootloder`.
	virtualisation.vmVariant = {		virtualisation.vmVariant = {
	# following configuration is added only when building VM with build-vm		# the following configuration is added only when building VM with `build-vm`
	virtualisation = {		virtualisation = {
	memorySize = 2048; # ~~Use~~ 2048MiB memory.		memorySize = 2048; # use 2048MiB memory
	cores = 3;		cores = 3; # use 3 cpu cores
	};		};
	}		}
	</syntaxhighlight>		</syntaxhighlight>

	~~Use <code>virtualisation.vmVariantWithBootLoader</code> option if you used <code>build-vm-with-bootloader</code> earlier.~~

	== Troubleshooting ==		== Troubleshooting ==

TornaxO7: Add subtitle and fix formatting

2025-09-24T09:10:15Z

Add subtitle and fix formatting

← Older revision		Revision as of 09:10, 24 September 2025
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	https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2		https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2

			== Configure Virtual Machine ==

	By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can set options <code>virtualisation.vmVariant.virtualisation.cores</code> and <code>virtualisation.vmVariant.virtualisation.memorySize</code> to enlarge the CPU cores and memory size for the virtual machine.		By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can set options <code>virtualisation.vmVariant.virtualisation.cores</code> and <code>virtualisation.vmVariant.virtualisation.memorySize</code> to enlarge the CPU cores and memory size for the virtual machine.
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	</syntaxhighlight>		</syntaxhighlight>

	Use <code>virtualisation.vmVariantWithBootLoader</code> option if you used `build-vm-with-bootloader` earlier.		Use <code>virtualisation.vmVariantWithBootLoader</code> option if you used <code>build-vm-with-bootloader</code> earlier.

	== Troubleshooting ==		== Troubleshooting ==

Pigs: Add category nixos

2025-05-18T17:56:39Z

Add category nixos

← Older revision		Revision as of 17:56, 18 May 2025
Line 94:		Line 94:

	[[Category:Virtualization]]		[[Category:Virtualization]]
			[[Category:NixOS]]

Pigs: Add category virtualization

2025-05-18T17:56:07Z

Add category virtualization

← Older revision		Revision as of 17:56, 18 May 2025
Line 92:		Line 92:
	</code>		</code>
	[https://discourse.nixos.org/t/nixos-rebuild-build-vm-not-portable-across-linux-distributions/28564/4 Source]		[https://discourse.nixos.org/t/nixos-rebuild-build-vm-not-portable-across-linux-distributions/28564/4 Source]

			[[Category:Virtualization]]

Raboof: how to expose a qemu VM port to the host

2025-02-27T18:07:59Z

how to expose a qemu VM port to the host

← Older revision		Revision as of 18:07, 27 February 2025
Line 49:		Line 49:
	When running a virtual machine a file called <code>$hostname.qcow2</code> is created in your current working directory. After changing your <code>/etc/nixos/configuration.nix</code> delete this file, rebuild and then start the new virtual machine. Now you should be able to login.		When running a virtual machine a file called <code>$hostname.qcow2</code> is created in your current working directory. After changing your <code>/etc/nixos/configuration.nix</code> delete this file, rebuild and then start the new virtual machine. Now you should be able to login.

			== Networking ==

			=== qemu ===

			To enable connecting from your host to your virtual machine, you'll need to forcefully override the default networking settings to apply those from https://wiki.qemu.org/Documentation/Networking#How_to_get_SSH_access_to_a_guest instead. For example, to expose the VM's port 80 on the (unprivileged) port 8009 of the 'localhost' of the host:

			<syntaxhighlight lang="nix">
			{ config, pkgs, lib, modulesPath, ... }:

			{
			imports = [
			(modulesPath + "/virtualisation/qemu-vm.nix")
			];

			virtualisation.qemu.networkingOptions = lib.mkForce [
			"-device e1000,netdev=net0"
			"-netdev user,id=net0,hostfwd=tcp:127.0.0.1:8009-:80,\${QEMU_NET_OPTS:+,$QEMU_NET_OPTS}"
			];

			networking.firewall.allowedTCPPorts = [
			80
			];
			}
			</syntaxhighlight>

	== Alternatives ==		== Alternatives ==

imported>Ibizaman: Add some info about build-vm-with-bootloader

2023-11-18T04:07:24Z

Add some info about build-vm-with-bootloader

← Older revision		Revision as of 04:07, 18 November 2023
Line 6:		Line 6:
	nixos-rebuild build-vm -I nixos-config=./configuration.nix -I nix_path='<nixpkgs/nixos>' --max-jobs 4 --show-trace # e.g. to specify the environment variables / cores used		nixos-rebuild build-vm -I nixos-config=./configuration.nix -I nix_path='<nixpkgs/nixos>' --max-jobs 4 --show-trace # e.g. to specify the environment variables / cores used
	</code>		</code>

			You can also use <code>build-vm-with-bootloader</code>. From the man page: this boots using the regular boot loader of your configuration rather than booting directly into the kernel and initial ramdisk of the system.

	You will not be able to login to this virtual machine, as the passwords are not carried over to the virtual machine you build.		You will not be able to login to this virtual machine, as the passwords are not carried over to the virtual machine you build.
Line 39:		Line 41:
	};		};
	}		}
			</syntaxhighlight>

	</~~syntaxhighlight~~>		Use <code>virtualisation.vmVariantWithBootLoader</code> option if you used `build-vm-with-bootloader` earlier.

	== Troubleshooting ==		== Troubleshooting ==

imported>Mcdonc: Get setting names right

2023-08-06T00:36:31Z

Get setting names right

← Older revision		Revision as of 00:36, 6 August 2023
Line 28:		Line 28:
	https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2		https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2

	By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can set options <code>virtualisation.vmVariant.cores</code> and <code>virtualisation.vmVariant.memorySize</code> to enlarge the CPU cores and memory size for the virtual machine.		By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can set options <code>virtualisation.vmVariant.virtualisation.cores</code> and <code>virtualisation.vmVariant.virtualisation.memorySize</code> to enlarge the CPU cores and memory size for the virtual machine.

	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">

imported>Mcdonc: Using virtualisation.cores and virtualisation.memorySize and importing virtualisation/qemu-vm.nix effectively tells Nix your host system is a VM, and all kinds of hilarity ensues... see https://github.com/NixOS/nixpkgs/issues/247413

2023-08-06T00:16:23Z

Using virtualisation.cores and virtualisation.memorySize and importing virtualisation/qemu-vm.nix effectively tells Nix your host system is a VM, and all kinds of hilarity ensues... see https://github.com/NixOS/nixpkgs/issues/247413

← Older revision		Revision as of 00:16, 6 August 2023
Line 28:		Line 28:
	https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2		https://discourse.nixos.org/t/default-login-and-password-for-nixos/4683/2

	By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can set options <code>virtualisation.cores</code> and <code>virtualisation.memorySize</code> to enlarge the CPU cores and memory size for the virtual machine~~. Note that due to [https://github.com/NixOS/nixpkgs/issues/59219 issue 59219], you need to import an extra module in order to use these options~~.		By default, the virtual machine is configured to have 1 CPU and 1024MiB memory. It may be too small for testing with desktop environment enabled inside. You can set options <code>virtualisation.vmVariant.cores</code> and <code>virtualisation.vmVariant.memorySize</code> to enlarge the CPU cores and memory size for the virtual machine.

	<syntaxhighlight lang="nix">		<syntaxhighlight lang="nix">
Line 38:		Line 38:
	cores = 3;		cores = 3;
	};		};
	};
	}		}
	~~</syntaxhighlight>~~

	or
	~~<syntaxhighlight lang="nix">~~
	{
	~~imports = [ <nixpkgs/nixos/modules/virtualisation/qemu-vm.nix> ];~~
	~~virtualisation = {~~
	~~memorySize = 2048; # Use 2048MiB memory.~~
	~~cores = 4; # Simulate 4 cores.~~
	};
	}
	</syntaxhighlight>		</syntaxhighlight>

imported>ErnstderLage: add alternative

2023-07-06T13:48:54Z

add alternative

← Older revision		Revision as of 13:48, 6 July 2023
Line 56:		Line 56:
	=== Still can't login after updating configuration ===		=== Still can't login after updating configuration ===
	When running a virtual machine a file called <code>$hostname.qcow2</code> is created in your current working directory. After changing your <code>/etc/nixos/configuration.nix</code> delete this file, rebuild and then start the new virtual machine. Now you should be able to login.		When running a virtual machine a file called <code>$hostname.qcow2</code> is created in your current working directory. After changing your <code>/etc/nixos/configuration.nix</code> delete this file, rebuild and then start the new virtual machine. Now you should be able to login.



			== Alternatives ==

			=== Bootable ISO ===
			Build it as a [https://nix.dev/tutorials/nixos/building-bootable-iso-image bootable ISO image]:

			=== VM ===
			<syntaxhighlight lang="nix">
			{
			...
			imports = [
			<nixos/nixos/modules/virtualisation/virtualbox-image.nix> ]
			...
			</syntaxhighlight>

			<code>
			nix build -f '<nixpkgs/nixos>' -I nixos-config=./configuration.nix config.system.build.virtualBoxOVA
			</code>
			[https://discourse.nixos.org/t/nixos-rebuild-build-vm-not-portable-across-linux-distributions/28564/4 Source]