pyrox.dev
1# This module creates netboot media containing the given NixOS
2# configuration.
3
4{ config, lib, pkgs, ... }:
5
6with lib;
7
8{
9 options = {
10
11 netboot.squashfsCompression = mkOption {
12 default = with pkgs.stdenv.hostPlatform; "xz -Xdict-size 100% "
13 + lib.optionalString isx86 "-Xbcj x86"
14 # Untested but should also reduce size for these platforms
15 + lib.optionalString isAarch "-Xbcj arm"
16 + lib.optionalString (isPower && is32bit && isBigEndian) "-Xbcj powerpc"
17 + lib.optionalString (isSparc) "-Xbcj sparc";
18 description = lib.mdDoc ''
19 Compression settings to use for the squashfs nix store.
20 '';
21 example = "zstd -Xcompression-level 6";
22 type = types.str;
23 };
24
25 netboot.storeContents = mkOption {
26 example = literalExpression "[ pkgs.stdenv ]";
27 description = lib.mdDoc ''
28 This option lists additional derivations to be included in the
29 Nix store in the generated netboot image.
30 '';
31 };
32
33 };
34
35 config = {
36 # Don't build the GRUB menu builder script, since we don't need it
37 # here and it causes a cyclic dependency.
38 boot.loader.grub.enable = false;
39
40 # !!! Hack - attributes expected by other modules.
41 environment.systemPackages = [ pkgs.grub2_efi ]
42 ++ (lib.optionals (pkgs.stdenv.hostPlatform.system != "aarch64-linux") [pkgs.grub2 pkgs.syslinux]);
43
44 fileSystems."/" = mkImageMediaOverride
45 { fsType = "tmpfs";
46 options = [ "mode=0755" ];
47 };
48
49 # In stage 1, mount a tmpfs on top of /nix/store (the squashfs
50 # image) to make this a live CD.
51 fileSystems."/nix/.ro-store" = mkImageMediaOverride
52 { fsType = "squashfs";
53 device = "../nix-store.squashfs";
54 options = [ "loop" ];
55 neededForBoot = true;
56 };
57
58 fileSystems."/nix/.rw-store" = mkImageMediaOverride
59 { fsType = "tmpfs";
60 options = [ "mode=0755" ];
61 neededForBoot = true;
62 };
63
64 fileSystems."/nix/store" = mkImageMediaOverride
65 { fsType = "overlay";
66 device = "overlay";
67 options = [
68 "lowerdir=/nix/.ro-store"
69 "upperdir=/nix/.rw-store/store"
70 "workdir=/nix/.rw-store/work"
71 ];
72
73 depends = [
74 "/nix/.ro-store"
75 "/nix/.rw-store/store"
76 "/nix/.rw-store/work"
77 ];
78 };
79
80 boot.initrd.availableKernelModules = [ "squashfs" "overlay" ];
81
82 boot.initrd.kernelModules = [ "loop" "overlay" ];
83
84 # Closures to be copied to the Nix store, namely the init
85 # script and the top-level system configuration directory.
86 netboot.storeContents =
87 [ config.system.build.toplevel ];
88
89 # Create the squashfs image that contains the Nix store.
90 system.build.squashfsStore = pkgs.callPackage ../../../lib/make-squashfs.nix {
91 storeContents = config.netboot.storeContents;
92 comp = config.netboot.squashfsCompression;
93 };
94
95
96 # Create the initrd
97 system.build.netbootRamdisk = pkgs.makeInitrdNG {
98 inherit (config.boot.initrd) compressor;
99 prepend = [ "${config.system.build.initialRamdisk}/initrd" ];
100
101 contents =
102 [ { object = config.system.build.squashfsStore;
103 symlink = "/nix-store.squashfs";
104 }
105 ];
106 };
107
108 system.build.netbootIpxeScript = pkgs.writeTextDir "netboot.ipxe" ''
109 #!ipxe
110 # Use the cmdline variable to allow the user to specify custom kernel params
111 # when chainloading this script from other iPXE scripts like netboot.xyz
112 kernel ${pkgs.stdenv.hostPlatform.linux-kernel.target} init=${config.system.build.toplevel}/init initrd=initrd ${toString config.boot.kernelParams} ''${cmdline}
113 initrd initrd
114 boot
115 '';
116
117 # A script invoking kexec on ./bzImage and ./initrd.gz.
118 # Usually used through system.build.kexecTree, but exposed here for composability.
119 system.build.kexecScript = pkgs.writeScript "kexec-boot" ''
120 #!/usr/bin/env bash
121 if ! kexec -v >/dev/null 2>&1; then
122 echo "kexec not found: please install kexec-tools" 2>&1
123 exit 1
124 fi
125 SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
126 kexec --load ''${SCRIPT_DIR}/bzImage \
127 --initrd=''${SCRIPT_DIR}/initrd.gz \
128 --command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
129 kexec -e
130 '';
131
132 # A tree containing initrd.gz, bzImage and a kexec-boot script.
133 system.build.kexecTree = pkgs.linkFarm "kexec-tree" [
134 {
135 name = "initrd.gz";
136 path = "${config.system.build.netbootRamdisk}/initrd";
137 }
138 {
139 name = "bzImage";
140 path = "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}";
141 }
142 {
143 name = "kexec-boot";
144 path = config.system.build.kexecScript;
145 }
146 ];
147
148 boot.loader.timeout = 10;
149
150 boot.postBootCommands =
151 ''
152 # After booting, register the contents of the Nix store
153 # in the Nix database in the tmpfs.
154 ${config.nix.package}/bin/nix-store --load-db < /nix/store/nix-path-registration
155
156 # nixos-rebuild also requires a "system" profile and an
157 # /etc/NIXOS tag.
158 touch /etc/NIXOS
159 ${config.nix.package}/bin/nix-env -p /nix/var/nix/profiles/system --set /run/current-system
160 '';
161
162 };
163
164}