pyrox.dev
1.Dd January 1, 1980
2.Dt nixos-generate-config 8
3.Os
4.Sh NAME
5.Nm nixos-generate-config
6.Nd generate NixOS configuration modules
7.
8.
9.
10.Sh SYNOPSIS
11.Nm nixos-generate-config
12.Op Fl -force
13.Op Fl -root Ar root
14.Op Fl -dir Ar dir
15.Op Fl -flake
16.Op Fl -kernel Ar <lts|latest>
17.
18.
19.
20.Sh DESCRIPTION
21This command writes two NixOS configuration modules:
22.Bl -tag -width indent
23.It Pa /etc/nixos/hardware-configuration.nix
24This module sets NixOS configuration options based on your current hardware
25configuration. In particular, it sets the
26.Va fileSystem
27option to reflect all currently mounted file systems, the
28.Va swapDevices
29option to reflect active swap devices, and the
30.Va boot.initrd.*
31options to ensure that the initial ramdisk contains any kernel modules necessary
32for mounting the root file system.
33.Pp
34If this file already exists, it is overwritten. Thus, you should not modify it
35manually. Rather, you should include it from your
36.Pa /etc/nixos/configuration.nix Ns
37, and re-run
38.Nm
39to update it whenever your hardware configuration changes.
40.
41.It Pa /etc/nixos/configuration.nix
42This is the main NixOS system configuration module. If it already exists, it’s
43left unchanged. Otherwise,
44.Nm
45will write a template for you to customise.
46.El
47.
48.
49.
50.Sh OPTIONS
51.Bl -tag -width indent
52.It Fl -root Ar root
53If this option is given, treat the directory
54.Ar root
55as the root of the file system. This means that configuration files will be written to
56.Ql Ar root Ns /etc/nixos Ns
57, and that any file systems outside of
58.Ar root
59are ignored for the purpose of generating the
60.Va fileSystems
61option.
62.
63.It Fl -dir Ar dir
64If this option is given, write the configuration files to the directory
65.Ar dir
66instead of
67.Pa /etc/nixos Ns
68\&.
69.
70.It Fl -kernel Ar <lts|latest>
71Set the kernel in the generated configuration file.
72.
73.It Fl -force
74Overwrite
75.Pa /etc/nixos/configuration.nix
76(and
77.Pa /etc/nixos/flake.nix
78if --flake is passed) if already present.
79.
80.It Fl -flake
81Also generate
82.Pa /etc/nixos/flake.nix Ns
83\&.
84.
85.It Fl -no-filesystems
86Omit everything concerning file systems and swap devices from the hardware configuration.
87.
88.It Fl -show-hardware-config
89Don't generate
90.Pa configuration.nix
91or
92.Pa hardware-configuration.nix
93and print the hardware configuration to stdout only.
94.El
95.
96.
97.
98.Sh EXAMPLES
99This command is typically used during NixOS installation to write initial
100configuration modules. For example, if you created and mounted the target file
101systems on
102.Pa /mnt
103and
104.Pa /mnt/boot Ns
105, you would run:
106.Bd -literal -offset indent
107$ nixos-generate-config --root /mnt
108.Ed
109.
110.Pp
111The resulting file
112.Pa /mnt/etc/nixos/hardware-configuration.nix
113might look like this:
114.Bd -literal -offset indent
115# Do not modify this file! It was generated by 'nixos-generate-config'
116# and may be overwritten by future invocations. Please make changes
117# to /etc/nixos/configuration.nix instead.
118{ config, pkgs, ... }:
119
120{
121 imports =
122 [ <nixos/modules/installer/scan/not-detected.nix>
123 ];
124
125 boot.initrd.availableKernelModules = [ "ehci_hcd" "ahci" ];
126 boot.kernelModules = [ "kvm-intel" ];
127 boot.extraModulePackages = [ ];
128
129 fileSystems."/" =
130 { device = "/dev/disk/by-label/nixos";
131 fsType = "ext3";
132 options = [ "rw" "data=ordered" "relatime" ];
133 };
134
135 fileSystems."/boot" =
136 { device = "/dev/sda1";
137 fsType = "ext3";
138 options = [ "rw" "errors=continue" "user_xattr" "acl" "barrier=1" "data=writeback" "relatime" ];
139 };
140
141 swapDevices =
142 [ { device = "/dev/sda2"; }
143 ];
144
145 nix.maxJobs = 8;
146}
147.Ed
148.
149.Pp
150It will also create a basic
151.Pa /mnt/etc/nixos/configuration.nix Ns
152, which you should edit to customise the logical configuration of your system. \
153This file includes the result of the hardware scan as follows:
154.Bd -literal -offset indent
155imports = [ ./hardware-configuration.nix ];
156.Ed
157.
158.Pp
159After installation, if your hardware configuration changes, you can run:
160.Bd -literal -offset indent
161$ nixos-generate-config
162.Ed
163.
164.Pp
165to update
166.Pa /etc/nixos/hardware-configuration.nix Ns
167\&. Your
168.Pa /etc/nixos/configuration.nix
169will
170.Em not
171be overwritten.
172.
173.Sh AUTHORS
174.An -nosplit
175.An Eelco Dolstra
176and
177.An the Nixpkgs/NixOS contributors