nixos-generate-config8NixOSnixos-generate-configgenerate NixOS configuration modulesnixos-generate-configrootdirDescription
This command writes two NixOS configuration modules:
This module sets NixOS configuration options based on your current
hardware configuration. In particular, it sets the
option to reflect all currently mounted file
systems, the option to reflect active swap
devices, and the options to ensure that
the initial ramdisk contains any kernel modules necessary for mounting
the root file system.
If this file already exists, it is overwritten. Thus, you should not
modify it manually. Rather, you should include it from your
/etc/nixos/configuration.nix, and re-run
nixos-generate-config to update it whenever your
hardware configuration changes.
This is the main NixOS system configuration module. If it already
exists, it’s left unchanged. Otherwise,
nixos-generate-config will write a template for you
to customise.
Options
This command accepts the following options:
If this option is given, treat the directory
root as the root of the file system. This
means that configuration files will be written to
root/etc/nixos, and that
any file systems outside of root are ignored
for the purpose of generating the option.
If this option is given, write the configuration files to the directory
dir instead of
/etc/nixos.
Overwrite /etc/nixos/configuration.nix if it already
exists.
Omit everything concerning file systems and swap devices from the
hardware configuration.
Don't generate configuration.nix or
hardware-configuration.nix and print the hardware
configuration to stdout only.
Examples
This command is typically used during NixOS installation to write initial
configuration modules. For example, if you created and mounted the target
file systems on /mnt and
/mnt/boot, you would run:
$ nixos-generate-config --root /mnt
The resulting file
/mnt/etc/nixos/hardware-configuration.nix might look
like this:
# Do not modify this file! It was generated by ‘nixos-generate-config’
# and may be overwritten by future invocations. Please make changes
# to /etc/nixos/configuration.nix instead.
{ config, pkgs, ... }:
{
imports =
[ <nixos/modules/installer/scan/not-detected.nix>
];
boot.initrd.availableKernelModules = [ "ehci_hcd" "ahci" ];
boot.kernelModules = [ "kvm-intel" ];
boot.extraModulePackages = [ ];
fileSystems."/" =
{ device = "/dev/disk/by-label/nixos";
fsType = "ext3";
options = [ "rw" "data=ordered" "relatime" ];
};
fileSystems."/boot" =
{ device = "/dev/sda1";
fsType = "ext3";
options = [ "rw" "errors=continue" "user_xattr" "acl" "barrier=1" "data=writeback" "relatime" ];
};
swapDevices =
[ { device = "/dev/sda2"; }
];
nix.maxJobs = 8;
}
It will also create a basic
/mnt/etc/nixos/configuration.nix, which you should edit
to customise the logical configuration of your system. This file includes
the result of the hardware scan as follows:
imports = [ ./hardware-configuration.nix ];
After installation, if your hardware configuration changes, you can run:
$ nixos-generate-config
to update /etc/nixos/hardware-configuration.nix. Your
/etc/nixos/configuration.nix will
not be overwritten.