148 lines
4.6 KiB
Nix
148 lines
4.6 KiB
Nix
# This module creates netboot media containing the given NixOS
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# configuration.
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{ config, lib, pkgs, ... }:
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with lib;
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{
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options = {
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netboot.squashfsCompression = mkOption {
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default = "zstd -Xcompression-level 19";
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description = ''
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Compression settings to use for the squashfs nix store.
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'';
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example = "zstd -Xcompression-level 6";
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type = types.str;
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};
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netboot.storeContents = mkOption {
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example = literalExpression "[ pkgs.stdenv ]";
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description = ''
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This option lists additional derivations to be included in the
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Nix store in the generated netboot image.
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'';
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};
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};
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config = {
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# Don't build the GRUB menu builder script, since we don't need it
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# here and it causes a cyclic dependency.
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boot.loader.grub.enable = false;
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fileSystems."/" = mkImageMediaOverride
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{ fsType = "tmpfs";
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options = [ "mode=0755" ];
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};
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# In stage 1, mount a tmpfs on top of /nix/store (the squashfs
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# image) to make this a live CD.
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fileSystems."/nix/.ro-store" = mkImageMediaOverride
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{ fsType = "squashfs";
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device = "../nix-store.squashfs";
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options = [ "loop" ] ++ lib.optional (config.boot.kernelPackages.kernel.kernelAtLeast "6.2") "threads=multi";
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neededForBoot = true;
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};
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fileSystems."/nix/.rw-store" = mkImageMediaOverride
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{ fsType = "tmpfs";
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options = [ "mode=0755" ];
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neededForBoot = true;
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};
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fileSystems."/nix/store" = mkImageMediaOverride
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{ overlay = {
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lowerdir = [ "/nix/.ro-store" ];
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upperdir = "/nix/.rw-store/store";
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workdir = "/nix/.rw-store/work";
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};
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neededForBoot = true;
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};
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boot.initrd.availableKernelModules = [ "squashfs" "overlay" ];
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boot.initrd.kernelModules = [ "loop" "overlay" ];
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# Closures to be copied to the Nix store, namely the init
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# script and the top-level system configuration directory.
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netboot.storeContents =
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[ config.system.build.toplevel ];
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# Create the squashfs image that contains the Nix store.
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system.build.squashfsStore = pkgs.callPackage ../../../lib/make-squashfs.nix {
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storeContents = config.netboot.storeContents;
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comp = config.netboot.squashfsCompression;
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};
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# Create the initrd
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system.build.netbootRamdisk = pkgs.makeInitrdNG {
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inherit (config.boot.initrd) compressor;
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prepend = [ "${config.system.build.initialRamdisk}/initrd" ];
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contents =
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[ { source = config.system.build.squashfsStore;
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target = "/nix-store.squashfs";
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}
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];
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};
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system.build.netbootIpxeScript = pkgs.writeTextDir "netboot.ipxe" ''
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#!ipxe
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# Use the cmdline variable to allow the user to specify custom kernel params
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# when chainloading this script from other iPXE scripts like netboot.xyz
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kernel ${pkgs.stdenv.hostPlatform.linux-kernel.target} init=${config.system.build.toplevel}/init initrd=initrd ${toString config.boot.kernelParams} ''${cmdline}
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initrd initrd
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boot
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'';
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# A script invoking kexec on ./bzImage and ./initrd.gz.
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# Usually used through system.build.kexecTree, but exposed here for composability.
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system.build.kexecScript = pkgs.writeScript "kexec-boot" ''
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#!/usr/bin/env bash
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if ! kexec -v >/dev/null 2>&1; then
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echo "kexec not found: please install kexec-tools" 2>&1
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exit 1
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fi
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SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
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kexec --load ''${SCRIPT_DIR}/bzImage \
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--initrd=''${SCRIPT_DIR}/initrd.gz \
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--command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
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kexec -e
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'';
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# A tree containing initrd.gz, bzImage and a kexec-boot script.
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system.build.kexecTree = pkgs.linkFarm "kexec-tree" [
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{
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name = "initrd.gz";
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path = "${config.system.build.netbootRamdisk}/initrd";
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}
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{
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name = "bzImage";
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path = "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}";
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}
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{
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name = "kexec-boot";
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path = config.system.build.kexecScript;
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}
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];
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boot.loader.timeout = 10;
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boot.postBootCommands =
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''
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# After booting, register the contents of the Nix store
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# in the Nix database in the tmpfs.
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${config.nix.package}/bin/nix-store --load-db < /nix/store/nix-path-registration
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# nixos-rebuild also requires a "system" profile and an
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# /etc/NIXOS tag.
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touch /etc/NIXOS
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${config.nix.package}/bin/nix-env -p /nix/var/nix/profiles/system --set /run/current-system
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'';
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};
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}
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