64589bcefa
Previously, `makeInitrd` added the whole closure of the squashfs derivation to initrd. This closure contains the squashfs.img and some store paths which are still referenced by the compressed squashfs.img. These extra store paths are unused in stage 1. With `makeInitrdNG` only the squashfs.img is added to the initrd. (`makeInitrdNG` only resolves shared library references instead of the whole closure). This shrinks the netboot ramdisk by ~6% for a minimal system and significantly decreases the size of the uncompressed root filesystem in stage 1.
121 lines
3.5 KiB
Nix
121 lines
3.5 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.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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# !!! Hack - attributes expected by other modules.
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environment.systemPackages = [ pkgs.grub2_efi ]
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++ (if pkgs.stdenv.hostPlatform.system == "aarch64-linux"
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then []
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else [ pkgs.grub2 pkgs.syslinux ]);
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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" ];
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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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{ fsType = "overlay";
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device = "overlay";
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options = [
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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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depends = [
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"/nix/.ro-store"
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"/nix/.rw-store/store"
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"/nix/.rw-store/work"
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];
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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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};
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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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[ { object = config.system.build.squashfsStore;
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symlink = "/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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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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