{ config, lib, pkgs, ... }: let keysDirectory = "/var/keys"; user = "builder"; keyType = "ed25519"; cfg = config.virtualisation.darwin-builder; in { imports = [ ../virtualisation/qemu-vm.nix # Avoid a dependency on stateVersion { disabledModules = [ ../virtualisation/nixos-containers.nix ../services/x11/desktop-managers/xterm.nix ]; config = { }; options.boot.isContainer = lib.mkOption { default = false; internal = true; }; } ]; options.virtualisation.darwin-builder = with lib; { diskSize = mkOption { default = 20 * 1024; type = types.int; example = 30720; description = "The maximum disk space allocated to the runner in MB"; }; memorySize = mkOption { default = 3 * 1024; type = types.int; example = 8192; description = "The runner's memory in MB"; }; min-free = mkOption { default = 1024 * 1024 * 1024; type = types.int; example = 1073741824; description = '' The threshold (in bytes) of free disk space left at which to start garbage collection on the runner ''; }; max-free = mkOption { default = 3 * 1024 * 1024 * 1024; type = types.int; example = 3221225472; description = '' The threshold (in bytes) of free disk space left at which to stop garbage collection on the runner ''; }; workingDirectory = mkOption { default = "."; type = types.str; example = "/var/lib/darwin-builder"; description = '' The working directory to use to run the script. When running as part of a flake will need to be set to a non read-only filesystem. ''; }; hostPort = mkOption { default = 22; type = types.int; example = 31022; description = '' The localhost host port to forward TCP to the guest port. ''; }; }; config = { # The builder is not intended to be used interactively documentation.enable = false; environment.etc = { "ssh/ssh_host_ed25519_key" = { mode = "0600"; source = ./keys/ssh_host_ed25519_key; }; "ssh/ssh_host_ed25519_key.pub" = { mode = "0644"; source = ./keys/ssh_host_ed25519_key.pub; }; }; # DNS fails for QEMU user networking (SLiRP) on macOS. See: # # https://github.com/utmapp/UTM/issues/2353 # # This works around that by using a public DNS server other than the DNS # server that QEMU provides (normally 10.0.2.3) networking.nameservers = [ "8.8.8.8" ]; nix.settings = { auto-optimise-store = true; min-free = cfg.min-free; max-free = cfg.max-free; trusted-users = [ "root" user ]; }; services = { getty.autologinUser = user; openssh = { enable = true; authorizedKeysFiles = [ "${keysDirectory}/%u_${keyType}.pub" ]; }; }; system.build.macos-builder-installer = let privateKey = "/etc/nix/${user}_${keyType}"; publicKey = "${privateKey}.pub"; # This installCredentials script is written so that it's as easy as # possible for a user to audit before confirming the `sudo` installCredentials = hostPkgs.writeShellScript "install-credentials" '' KEYS="''${1}" INSTALL=${hostPkgs.coreutils}/bin/install "''${INSTALL}" -g nixbld -m 600 "''${KEYS}/${user}_${keyType}" ${privateKey} "''${INSTALL}" -g nixbld -m 644 "''${KEYS}/${user}_${keyType}.pub" ${publicKey} ''; hostPkgs = config.virtualisation.host.pkgs; script = hostPkgs.writeShellScriptBin "create-builder" ( # When running as non-interactively as part of a DarwinConfiguration the working directory # must be set to a writeable directory. (if cfg.workingDirectory != "." then '' ${hostPkgs.coreutils}/bin/mkdir --parent "${cfg.workingDirectory}" cd "${cfg.workingDirectory}" '' else "") + '' KEYS="''${KEYS:-./keys}" ${hostPkgs.coreutils}/bin/mkdir --parent "''${KEYS}" PRIVATE_KEY="''${KEYS}/${user}_${keyType}" PUBLIC_KEY="''${PRIVATE_KEY}.pub" if [ ! -e "''${PRIVATE_KEY}" ] || [ ! -e "''${PUBLIC_KEY}" ]; then ${hostPkgs.coreutils}/bin/rm --force -- "''${PRIVATE_KEY}" "''${PUBLIC_KEY}" ${hostPkgs.openssh}/bin/ssh-keygen -q -f "''${PRIVATE_KEY}" -t ${keyType} -N "" -C 'builder@localhost' fi if ! ${hostPkgs.diffutils}/bin/cmp "''${PUBLIC_KEY}" ${publicKey}; then (set -x; sudo --reset-timestamp ${installCredentials} "''${KEYS}") fi KEYS="$(${hostPkgs.nix}/bin/nix-store --add "$KEYS")" ${config.system.build.vm}/bin/run-nixos-vm ''); in script.overrideAttrs (old: { meta = (old.meta or { }) // { platforms = lib.platforms.darwin; }; }); system = { # To prevent gratuitous rebuilds on each change to Nixpkgs nixos.revision = null; stateVersion = lib.mkDefault (throw '' The macOS linux builder should not need a stateVersion to be set, but a module has accessed stateVersion nonetheless. Please inspect the trace of the following command to figure out which module has a dependency on stateVersion. nix-instantiate --attr darwin.builder --show-trace ''); }; users.users."${user}" = { isNormalUser = true; }; security.polkit.enable = true; security.polkit.extraConfig = '' polkit.addRule(function(action, subject) { if (action.id === "org.freedesktop.login1.power-off" && subject.user === "${user}") { return "yes"; } else { return "no"; } }) ''; virtualisation = { diskSize = cfg.diskSize; memorySize = cfg.memorySize; forwardPorts = [ { from = "host"; guest.port = 22; host.port = cfg.hostPort; } ]; # Disable graphics for the builder since users will likely want to run it # non-interactively in the background. graphics = false; sharedDirectories.keys = { source = "\"$KEYS\""; target = keysDirectory; }; # If we don't enable this option then the host will fail to delegate builds # to the guest, because: # # - The host will lock the path to build # - The host will delegate the build to the guest # - The guest will attempt to lock the same path and fail because # the lockfile on the host is visible on the guest # # Snapshotting the host's /nix/store as an image isolates the guest VM's # /nix/store from the host's /nix/store, preventing this problem. useNixStoreImage = true; # Obviously the /nix/store needs to be writable on the guest in order for it # to perform builds. writableStore = true; # This ensures that anything built on the guest isn't lost when the guest is # restarted. writableStoreUseTmpfs = false; }; }; }