nixpkgs/nixos/modules/installer/netboot/netboot.nix

152 lines
4.6 KiB
Nix

# This module creates netboot media containing the given NixOS
# configuration.
{ config, lib, pkgs, ... }:
with lib;
{
options = {
netboot.storeContents = mkOption {
example = literalExpression "[ pkgs.stdenv ]";
description = lib.mdDoc ''
This option lists additional derivations to be included in the
Nix store in the generated netboot image.
'';
};
};
config = {
# 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;
# !!! Hack - attributes expected by other modules.
environment.systemPackages = [ pkgs.grub2_efi ]
++ (if pkgs.stdenv.hostPlatform.system == "aarch64-linux"
then []
else [ pkgs.grub2 pkgs.syslinux ]);
fileSystems."/" = mkImageMediaOverride
{ fsType = "tmpfs";
options = [ "mode=0755" ];
};
# In stage 1, mount a tmpfs on top of /nix/store (the squashfs
# image) to make this a live CD.
fileSystems."/nix/.ro-store" = mkImageMediaOverride
{ fsType = "squashfs";
device = "../nix-store.squashfs";
options = [ "loop" ];
neededForBoot = true;
};
fileSystems."/nix/.rw-store" = mkImageMediaOverride
{ fsType = "tmpfs";
options = [ "mode=0755" ];
neededForBoot = true;
};
fileSystems."/nix/store" = mkImageMediaOverride
{ fsType = "overlay";
device = "overlay";
options = [
"lowerdir=/nix/.ro-store"
"upperdir=/nix/.rw-store/store"
"workdir=/nix/.rw-store/work"
];
depends = [
"/nix/.ro-store"
"/nix/.rw-store/store"
"/nix/.rw-store/work"
];
};
boot.initrd.availableKernelModules = [ "squashfs" "overlay" ];
boot.initrd.kernelModules = [ "loop" "overlay" ];
# 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 = pkgs.callPackage ../../../lib/make-squashfs.nix {
storeContents = config.netboot.storeContents;
};
# Create the initrd
system.build.netbootRamdisk = pkgs.makeInitrdNG {
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
# Use the cmdline variable to allow the user to specify custom kernel params
# when chainloading this script from other iPXE scripts like netboot.xyz
kernel ${pkgs.stdenv.hostPlatform.linux-kernel.target} init=${config.system.build.toplevel}/init initrd=initrd ${toString config.boot.kernelParams} ''${cmdline}
initrd initrd
boot
'';
# A script invoking kexec on ./bzImage and ./initrd.gz.
# Usually used through system.build.kexecTree, but exposed here for composability.
system.build.kexecScript = pkgs.writeScript "kexec-boot" ''
#!/usr/bin/env bash
if ! kexec -v >/dev/null 2>&1; then
echo "kexec not found: please install kexec-tools" 2>&1
exit 1
fi
SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
kexec --load ''${SCRIPT_DIR}/bzImage \
--initrd=''${SCRIPT_DIR}/initrd.gz \
--command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
kexec -e
'';
# A tree containing initrd.gz, bzImage and a kexec-boot script.
system.build.kexecTree = pkgs.linkFarm "kexec-tree" [
{
name = "initrd.gz";
path = "${config.system.build.netbootRamdisk}/initrd";
}
{
name = "bzImage";
path = "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}";
}
{
name = "kexec-boot";
path = config.system.build.kexecScript;
}
];
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
'';
};
}