installer: simple PXE bootable NixOS installer

The Nix store squashfs is stored inside the initrd instead of separately

(cherry picked from commit 976fd407796877b538c470d3a5253ad3e1f7bc68)
Signed-off-by: Domen Kožar <domen@dev.si>

1 files changed, 91 insertions, 0 deletions

diff --git a/nixos/modules/installer/netboot/netboot.nix b/nixos/modules/installer/netboot/netboot.nix
new file mode 100644
index 00000000000..366591a8114
--- /dev/null
+++ b/nixos/modules/installer/netboot/netboot.nix
@@ -0,0 +1,91 @@
+# This module creates netboot media containing the given NixOS
+# configuration.
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  options = {
+
+    netboot.storeContents = mkOption {
+      example = literalExample "[ pkgs.stdenv ]";
+      description = ''
+        This option lists additional derivations to be included in the
+        Nix store in the generated netboot image.
+      '';
+    };
+
+  };
+
+  config = {
+
+    boot.loader.grub.version = 2;
+
+    # Don't build the GRUB menu builder script, since we don't need it
+    # here and it causes a cyclic dependency.
+    boot.loader.grub.enable = false;
+
+    boot.initrd.postMountCommands = ''
+      mkdir -p /mnt-root/nix/store
+      mount -t squashfs /nix-store.squashfs /mnt-root/nix/store
+    '';
+
+    # !!! Hack - attributes expected by other modules.
+    system.boot.loader.kernelFile = "bzImage";
+    environment.systemPackages = [ pkgs.grub2 pkgs.grub2_efi pkgs.syslinux ];
+
+    boot.consoleLogLevel = mkDefault 7;
+
+    fileSystems."/" =
+      { fsType = "tmpfs";
+        options = [ "mode=0755" ];
+      };
+
+    boot.initrd.availableKernelModules = [ "squashfs" ];
+
+    boot.initrd.kernelModules = [ "loop" ];
+
+    # Closures to be copied to the Nix store, namely the init
+    # script and the top-level system configuration directory.
+   netboot.storeContents =
+      [ config.system.build.toplevel ];
+
+    # Create the squashfs image that contains the Nix store.
+    system.build.squashfsStore = import ../../../lib/make-squashfs.nix {
+      inherit (pkgs) stdenv squashfsTools perl pathsFromGraph;
+      storeContents = config.netboot.storeContents;
+    };
+
+
+    # Create the initrd
+    system.build.netbootRamdisk = pkgs.makeInitrd {
+      inherit (config.boot.initrd) compressor;
+      prepend = [ "${config.system.build.initialRamdisk}/initrd" ];
+
+      contents =
+        [ { object = config.system.build.squashfsStore;
+            symlink = "/nix-store.squashfs";
+          }
+        ];
+    };
+
+    system.build.netbootIpxeScript = pkgs.writeTextDir "netboot.ipxe" "#!ipxe\nkernel bzImage init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}\ninitrd initrd\nboot";
+
+    boot.loader.timeout = 10;
+
+    boot.postBootCommands =
+      ''
+        # After booting, register the contents of the Nix store
+        # in the Nix database in the tmpfs.
+        ${config.nix.package}/bin/nix-store --load-db < /nix/store/nix-path-registration
+
+        # nixos-rebuild also requires a "system" profile and an
+        # /etc/NIXOS tag.
+        touch /etc/NIXOS
+        ${config.nix.package}/bin/nix-env -p /nix/var/nix/profiles/system --set /run/current-system
+      '';
+
+  };
+
+}