nixpkgs/nixos/modules/profiles/macos-builder.nix
2023-04-07 05:10:49 +02:00

240 lines
7.0 KiB
Nix

{ 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;
};
};
}