disko-install

disko-install enhances the normal nixos-install with disko's partitioning feature. It can be started from the NixOS installer but it can also be used to create bootable USB-Sticks from your normal workstation. Furthermore disko-install has a mount mode that will only mount but not destroy existing partitions. The mount mode can be used to mount and repair existing NixOS installations. This document provides a comprehensive guide on how to use disko-install, including examples for typical usage scenarios.

Requirements

a Linux system with Nix installed.
a target disk or partition for the NixOS installation.
a Nix flake that defines your desired NixOS configuration.

Usage

Fresh Installation

For a fresh installation, where disko-install will handle partitioning and setting up the disk, use the following syntax:

sudo nix run 'github:nix-community/disko/latest#disko-install' -- --flake <flake-url>#<flake-attr> --disk <disk-name> <disk-device>

Example:

First run nixos-generate-config --root /tmp/config --no-filesystems and edit configuration.nix to your liking.

Then add the following flake.nix inside /tmp/config/etc/nixos. In this example we assume a system that has been booted with EFI:

{
  inputs.nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
  inputs.disko.url = "github:nix-community/disko/latest";
  inputs.disko.inputs.nixpkgs.follows = "nixpkgs";

  outputs = { self, disko, nixpkgs }: {
    nixosConfigurations.mymachine = nixpkgs.legacyPackages.x86_64-linux.nixos [
      ./configuration.nix
      disko.nixosModules.disko
      {
        disko.devices = {
          disk = {
            main = {
              # When using disko-install, we will overwrite this value from the commandline
              device = "/dev/disk/by-id/some-disk-id";
              type = "disk";
              content = {
                type = "gpt";
                partitions = {
                  MBR = {
                    type = "EF02"; # for grub MBR
                    size = "1M";
                    priority = 1; # Needs to be first partition
                  };
                  ESP = {
                    type = "EF00";
                    size = "500M";
                    content = {
                      type = "filesystem";
                      format = "vfat";
                      mountpoint = "/boot";
                      mountOptions = [ "umask=0077" ];
                    };
                  };
                  root = {
                    size = "100%";
                    content = {
                      type = "filesystem";
                      format = "ext4";
                      mountpoint = "/";
                    };
                  };
                };
              };
            };
          };
        };
      }
    ];
  };
}

Identify the device name that you want to install NixOS to:

$ lsblk
NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda           8:0    1 14.9G  0 disk
└─sda1        8:1    1 14.9G  0 part
zd0         230:0    0   10G  0 disk
├─zd0p1     230:1    0  500M  0 part
└─zd0p2     230:2    0  9.5G  0 part /mnt
nvme0n1     259:0    0  1.8T  0 disk
├─nvme0n1p1 259:1    0    1G  0 part /boot
├─nvme0n1p2 259:2    0   16M  0 part
├─nvme0n1p3 259:3    0  250G  0 part
└─nvme0n1p4 259:4    0  1.6T  0 part

In our example, we want to install to a USB-stick (/dev/sda):

$ sudo nix run 'github:nix-community/disko/latest#disko-install' -- --flake '/tmp/config/etc/nixos#mymachine' --disk main /dev/sda

Afterwards you can test your USB-stick by either selecting during the boot or attaching it to a qemu-vm:

$ sudo qemu-kvm -enable-kvm -hda /dev/sda

Persisting boot entries to EFI vars flash

disko-install is designed for NixOS installations on portable storage or disks that may be transferred between computers. As such, it does not modify the host's NVRAM by default. To ensure your NixOS installation boots seamlessly on new hardware or to prioritize it in your current machine's boot order, use the --write-efi-boot-entries option:

$ sudo nix run 'github:nix-community/disko/latest#disko-install' -- --write-efi-boot-entries --flake '/tmp/config/etc/nixos#mymachine' --disk main /dev/sda

This command installs NixOS with disko-install and sets the newly installed system as the default boot option, without affecting the flexibility to boot from other devices if needed.

Using disko-install in an offline installer

If you want to use disko-install from a custom installer without internet, you need to make sure that in addition to the toplevel of your NixOS closure that you plan to install, it also needs to contain diskoScript and all the flake inputs for evaluation.

Example configuration to install

Add this to your flake.nix output:

{
  nixosConfigurations.your-machine = inputs.nixpkgs.lib.nixosSystem {
    system = "x86_64-linux";
    # to pass this flake into your configuration (see the example below)
    specialArgs = {inherit self;};
    modules = [
      {
        # TODO: add your NixOS configuration here, don't forget your hardware-configuration.nix as well!
        boot.loader.systemd-boot.enable = true;
        imports = [ self.inputs.disko.nixosModules.disko ];
        disko.devices = {
          disk = {
            vdb = {
              device = "/dev/disk/by-id/some-disk-id";
              type = "disk";
              content = {
                type = "gpt";
                partitions = {
                  ESP = {
                    type = "EF00";
                    size = "500M";
                    content = {
                      type = "filesystem";
                      format = "vfat";
                      mountpoint = "/boot";
                      mountOptions = [ "umask=0077" ];
                    };
                  };
                  root = {
                    size = "100%";
                    content = {
                      type = "filesystem";
                      format = "ext4";
                      mountpoint = "/";
                    };
                  };
                };
              };
            };
          };
        };
      }
    ];
  };
}

Example for a NixOS installer

# `self` here is referring to the flake `self`, you may need to pass it using `specialArgs` or define your NixOS installer configuration
# in the flake.nix itself to get direct access to the `self` flake variable.
{ pkgs, self, ... }:
let
  dependencies = [
    self.nixosConfigurations.your-machine.config.system.build.toplevel
    self.nixosConfigurations.your-machine.config.system.build.diskoScript
    self.nixosConfigurations.your-machine.config.system.build.diskoScript.drvPath
    self.nixosConfigurations.your-machine.pkgs.stdenv.drvPath

    # https://github.com/NixOS/nixpkgs/blob/f2fd33a198a58c4f3d53213f01432e4d88474956/nixos/modules/system/activation/top-level.nix#L342
    self.nixosConfigurations.your-machine.pkgs.perlPackages.ConfigIniFiles
    self.nixosConfigurations.your-machine.pkgs.perlPackages.FileSlurp

    (self.nixosConfigurations.your-machine.pkgs.closureInfo { rootPaths = [ ]; }).drvPath
  ] ++ builtins.map (i: i.outPath) (builtins.attrValues self.inputs);

  closureInfo = pkgs.closureInfo { rootPaths = dependencies; };
in
# Now add `closureInfo` to your NixOS installer
{
  environment.etc."install-closure".source = "${closureInfo}/store-paths";

  environment.systemPackages = [
    (pkgs.writeShellScriptBin "install-nixos-unattended" ''
      set -eux
      # Replace "/dev/disk/by-id/some-disk-id" with your actual disk ID
      exec ${pkgs.disko}/bin/disko-install --flake "${self}#your-machine" --disk vdb "/dev/disk/by-id/some-disk-id"
    '')
  ];
}

Also see the NixOS test of disko-install that also runs without internet.

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