Difference between revisions of "Creating a NixOS live CD"

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(isos do now have zfs again)
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==Motivation==
+
== Motivation ==
 
Creating a modified NixOS LiveCD out of an existing working NixOS installation has a number of benefits:
 
Creating a modified NixOS LiveCD out of an existing working NixOS installation has a number of benefits:
 
* Ensures authenticity.
 
* Ensures authenticity.
Line 5: Line 5:
 
* It is easy to add your own packages and configuration changes to the image.
 
* It is easy to add your own packages and configuration changes to the image.
  
−
==Building==
+
== Building ==
 +
 
 +
Building minimal NixOS installation CD with the <code>nix-build</code> command by creating this <code>iso.nix</code>-file. In this example with [[Neovim]] preinstalled.
  
−
Create a file <tt>iso.nix</tt>:
 
 
<syntaxhighlight lang="nix">
 
<syntaxhighlight lang="nix">
−
# This module defines a small NixOS installation CD.  It does not
+
{ config, pkgs, ... }:
−
# contain any graphical stuff.
 
−
{config, pkgs, ...}:
 
 
{
 
{
 
   imports = [
 
   imports = [
Line 20: Line 19:
 
     <nixpkgs/nixos/modules/installer/cd-dvd/channel.nix>
 
     <nixpkgs/nixos/modules/installer/cd-dvd/channel.nix>
 
   ];
 
   ];
 +
  environment.systemPackages = [ pkgs.neovim ];
 
}
 
}
 
</syntaxhighlight>
 
</syntaxhighlight>
Line 27: Line 27:
 
<syntaxhighlight lang="bash">
 
<syntaxhighlight lang="bash">
 
nix-build '<nixpkgs/nixos>' -A config.system.build.isoImage -I nixos-config=iso.nix
 
nix-build '<nixpkgs/nixos>' -A config.system.build.isoImage -I nixos-config=iso.nix
 +
</syntaxhighlight>
 +
 +
Alternativley, use Nix [[Flakes]] to generate a ISO installation image, using the <code>23.11-beta</code> branch as nixpkgs source:
 +
 +
{{file|flake.nix|nix|<nowiki>
 +
{
 +
  description = "Minimal NixOS installation media";
 +
  inputs.nixos.url = "nixpkgs/23.11-beta";
 +
  outputs = { self, nixos }: {
 +
    nixosConfigurations = {
 +
      exampleIso = nixos.lib.nixosSystem {
 +
        system = "x86_64-linux";
 +
        modules = [
 +
          "${nixos}/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix"
 +
          ({ pkgs, ... }: {
 +
            environment.systemPackages = [ pkgs.neovim ];
 +
          })
 +
        ];
 +
      };
 +
    };
 +
  };
 +
}
 +
</nowiki>}}
 +
 +
The following commands will generate the iso-image
 +
 +
<syntaxhighlight lang="console">
 +
# git init
 +
# git add flake.nix
 +
# nix build .#nixosConfigurations.exampleIso.config.system.build.isoImage
 
</syntaxhighlight>
 
</syntaxhighlight>
  
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</syntaxhighlight>
 
</syntaxhighlight>
  
 +
=== Testing the image ===
 +
 +
To inspect the contents of the ISO image:
 +
 +
<syntaxhighlight lang="console">
 +
$ mkdir mnt
 +
$ sudo mount -o loop result/iso/nixos-*.iso mnt
 +
$ ls mnt
 +
boot  EFI  isolinux  nix-store.squashfs  version.txt
 +
$ umount mnt
 +
</syntaxhighlight>
 +
 +
To boot the ISO image in an emulator:
 +
 +
<syntaxhighlight lang="console">
 +
$ nix-shell -p qemu
 +
$ qemu-system-x86_64 -enable-kvm -m 256 -cdrom result/iso/nixos-*.iso
 +
</syntaxhighlight>
  
 
===SSH===
 
===SSH===
Line 72: Line 120:
 
</syntaxhighlight>
 
</syntaxhighlight>
  
 +
=== Building faster ===
 +
The build process is slow because of compression.
 +
 +
Here are some timings for <code>nix-build</code>:
 +
 +
{| class="wikitable" style="margin:auto"
 +
|+ Compression results
 +
|-
 +
! squashfsCompression !! Time !! Size
 +
|-
 +
| <code>lz4</code> || 100s || 59%
 +
|-
 +
| <code>gzip -Xcompression-level 1</code> || 105s || 52%
 +
|-
 +
| <code>gzip</code> || 210s || 49%
 +
|-
 +
| <code>xz -Xdict-size 100%</code> (default) || 450s || 43%
 +
|}
 +
 +
See also: [https://gist.github.com/baryluk/70a99b5f26df4671378dd05afef97fce mksquashfs benchmarks]
 +
 +
If you don't care about file size, you can use a faster compression
 +
by adding this to your <code>iso.nix</code>:
 +
 +
<syntaxhighlight lang="nix">
 +
{
 +
  isoImage.squashfsCompression = "gzip -Xcompression-level 1";
 +
}
 +
</syntaxhighlight>
  
 
==See also==
 
==See also==
−
* [https://nixos.org/nixos/manual/index.html#sec-building-cd NixOS Manual: Building your own CD].
+
* [https://nixos.org/manual/nixos/stable/index.html#sec-building-image NixOS Manual: Building a NixOS (Live) ISO].
  
 
[[Category:NixOS]]
 
[[Category:NixOS]]
 
[[Category:Installation]]
 
[[Category:Installation]]
 
[[Category:Deployment]]
 
[[Category:Deployment]]
−
[[Category:Guide]]
+
[[Category:Cookbook]]

Latest revision as of 10:53, 6 April 2024

Motivation

Creating a modified NixOS LiveCD out of an existing working NixOS installation has a number of benefits:

  • Ensures authenticity.
  • No need for internet access.
  • It is easy to add your own packages and configuration changes to the image.

Building

Building minimal NixOS installation CD with the nix-build command by creating this iso.nix-file. In this example with Neovim preinstalled. 

{ config, pkgs, ... }:
{
  imports = [
    <nixpkgs/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix>

    # Provide an initial copy of the NixOS channel so that the user
    # doesn't need to run "nix-channel --update" first.
    <nixpkgs/nixos/modules/installer/cd-dvd/channel.nix>
  ];
  environment.systemPackages = [ pkgs.neovim ];
}

Build the image via: 

nix-build '<nixpkgs/nixos>' -A config.system.build.isoImage -I nixos-config=iso.nix

Alternativley, use Nix Flakes to generate a ISO installation image, using the 23.11-beta branch as nixpkgs source:

Breeze-text-x-plain.png
flake.nix

{
  description = "Minimal NixOS installation media";
  inputs.nixos.url = "nixpkgs/23.11-beta";
  outputs = { self, nixos }: {
    nixosConfigurations = {
      exampleIso = nixos.lib.nixosSystem {
        system = "x86_64-linux";
        modules = [
          "${nixos}/nixos/modules/installer/cd-dvd/installation-cd-minimal.nix"
          ({ pkgs, ... }: {
            environment.systemPackages = [ pkgs.neovim ];
          })
        ];
      };
    };
  };
}


The following commands will generate the iso-image 

# git init
# git add flake.nix
# nix build .#nixosConfigurations.exampleIso.config.system.build.isoImage

The resulting image can be found in result: 

$ ls result/iso/
nixos-17.09.git.158ec57-x86_64-linux.iso

Testing the image

To inspect the contents of the ISO image: 

$ mkdir mnt
$ sudo mount -o loop result/iso/nixos-*.iso mnt
$ ls mnt
boot  EFI  isolinux  nix-store.squashfs  version.txt
$ umount mnt

To boot the ISO image in an emulator: 

$ nix-shell -p qemu
$ qemu-system-x86_64 -enable-kvm -m 256 -cdrom result/iso/nixos-*.iso

SSH

In your iso.nix: 

{
  ...
  # Enable SSH in the boot process.
  systemd.services.sshd.wantedBy = pkgs.lib.mkForce [ "multi-user.target" ];
  users.users.root.openssh.authorizedKeys.keys = [
    "ssh-ed25519 AaAeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee username@host"
  ];
  ...
}

Static IP Address

Static IP addresses can be set in the image itself. This can be useful for VPS installation. 

{
  ...
  networking = {
    usePredictableInterfaceNames = false;
    interfaces.eth0.ip4 = [{
      address = "64.137.201.46";
      prefixLength = 24;
    }];
    defaultGateway = "64.137.201.1";
    nameservers = [ "8.8.8.8" ];
  };
  ...
}

Building faster

The build process is slow because of compression.

Here are some timings for nix-build:

Compression results
squashfsCompression Time Size
lz4 100s 59%
gzip -Xcompression-level 1 105s 52%
gzip 210s 49%
xz -Xdict-size 100% (default) 450s 43%

See also: mksquashfs benchmarks

If you don't care about file size, you can use a faster compression by adding this to your iso.nix: 

{
  isoImage.squashfsCompression = "gzip -Xcompression-level 1";
}

See also

Retrieved from "https://nixos.wiki/index.php?title=Creating_a_NixOS_live_CD&oldid=12319"