ALPHA: wire is a tool to deploy nixos systems
wire.althaea.zone/
althaea.zone
1---
2comment: true
3title: Creating a Virtual Machine
4description: Creating a NixOS virtual machine to use as a deployment target.
5---
6
7# Creating a Virtual Machine
8
9{{ $frontmatter.description }}
10
11## Creating a `vm.nix`
12
13For this step, you'll need your ssh public key, which you can obtain from
14`ssh-add -L`.
15
16Open a text editor and edit `vm.nix`. Place in it this basic NixOS
17virtual machine configuration, which enables openssh and forwards it's 22 port:
18
19```nix:line-numbers [vm.nix]
20let
21 sources = import ./npins;
22in
23{
24 imports = [ "${sources.nixpkgs}/nixos/modules/virtualisation/qemu-vm.nix" ];
25
26 networking.hostName = "wire-tutorial";
27
28 users.users.root = {
29 initialPassword = "root";
30 openssh.authorizedKeys.keys = [
31 # I made this a nix syntax error so you're forced to deal with it!
32 <your ssh public-key as a string>
33 ];
34 };
35
36 boot = {
37 loader = {
38 systemd-boot.enable = true;
39 efi.canTouchEfiVariables = true;
40 };
41
42 kernelParams = [ "console=ttyS0" ];
43
44 boot.growPartition = true;
45 };
46
47 # enable openssh
48 services = {
49 openssh = {
50 enable = true;
51 settings.PermitRootLogin = "yes";
52 };
53
54 getty.autologinUser = "root";
55 };
56
57 virtualisation = {
58 graphics = false;
59 useBootLoader = true;
60
61 # use a 5gb disk
62 diskSize = 5 * 1024;
63
64 # grow the filesystem to fit the 5 gb we reserved
65 fileSystems."/".autoResize = true;
66
67 # forward `openssh` port 22 to localhost:2222.
68 forwardPorts = [
69 {
70 from = "host";
71 host.port = 2222;
72 guest.port = 22;
73 }
74 ];
75 };
76
77 system.stateVersion = "23.11";
78}
79```
80
81If you like, you may take a moment to understand each line of this
82configuration.
83
84## Building & Running the virtual machine
85
86Open a separate Terminal tab/window/instance, ensuring you enter the development
87shell with `nix-shell`.
88Then, build the virtual machine with a bootloader,
89taking our `vm.nix` as the nixos configuration.
90
91```sh
92$ nix-shell
93[nix-shell]$ nix-build '<nixpkgs/nixos>' -A vmWithBootLoader -I nixos-config=./vm.nix
94```
95
96::: tip HELP
97
98If you got an error such as
99
100```
101error: The option `...' in `...' is already declared in `...'.
102```
103
104make sure you ran the above command in the `nix-shell`!
105
106:::
107
108Building the virtual machine can take some time, but once it completes, start it
109by running:
110
111```sh
112[nix-shell]$ ./result/bin/run-wire-tutorial-vm
113```
114
115You will see boot-up logs fly across the screen and eventually you will be placed
116into shell inside the virtual machine.
117
118```sh [Virtual Machine]
119running activation script...
120setting up /etc...
121
122Welcome to NixOS 25.11 (Xantusia)!
123
124[ OK ] Created slice Slice /system/getty.
125[ OK ] Created slice Slice /system/modprobe.
126...
127<<< Welcome to NixOS 25.11pre861972.88cef159e47c (x86_64) - hvc0 >>>
128
129Run 'nixos-help' for the NixOS manual.
130
131wire-tutorial login: root (automatic login)
132
133[root@wire-tutorial:~]#
134
135```
136
137::: details
138Further details on how the above commands work can be found at
139[nix.dev](https://nix.dev/tutorials/nixos/nixos-configuration-on-vm.html#creating-a-qemu-based-virtual-machine-from-a-nixos-configuration)
140:::
141
142## Summary
143
144Congratulations, you created a virtual machine in your terminal.
145We'll be deploying to this virtual machine, so keep the
146terminal instance open.
147
148::: info
149From now on, commands ran inside the virtual machine will be lead with the
150following prompt:
151
152```sh [Virtual Machine]
153[root@wire-tutorial:~]#
154
155```
156
157:::
158
159::: tip
160If you ever want to quit the virtual machine, run the command `poweroff`.
161:::