Merge pull request #334526 from ElvishJerricco/revert-boot-counting-again-sadface

- `hardware.display` is a new module implementing workarounds for misbehaving monitors

  through setting up custom EDID files and forcing kernel/framebuffer modes.

- NixOS now has support for *automatic boot assessment* (see [here](https://systemd.io/AUTOMATIC_BOOT_ASSESSMENT/)) for detailed description of the feature) for `systemd-boot` users. Available as [boot.loader.systemd-boot.bootCounting](#opt-boot.loader.systemd-boot.bootCounting.enable).

- A new display-manager `services.displayManager.ly` was added.

  It is a tui based replacement of sddm and lightdm for window manager users.

  Users can use it by `services.displayManager.ly.enable` and config it by

{ config, lib, extendModules, noUserModules, ... }:

{ config, lib, pkgs, extendModules, noUserModules, ... }:

let

  inherit (lib)

    attrNames

    concatStringsSep

    filter

    length

    mapAttrs

    mapAttrsToList

    match

    mkOption

    types

    ;

  };

  config = {

    assertions = [(

      let

        invalidNames = filter (name: match "[[:alnum:]_]+" name == null) (attrNames config.specialisation);

      in

      {

        assertion = length invalidNames == 0;

        message = ''

          Specialisation names can only contain alphanumeric characters and underscores

          Invalid specialisation names: ${concatStringsSep ", " invalidNames}

        '';

      }

    )];

    system.systemBuilderCommands = ''

      mkdir $out/specialisation

      ${concatStringsSep "\n"

# Automatic boot assessment with systemd-boot {#sec-automatic-boot-assessment}

## Overview {#sec-automatic-boot-assessment-overview}

Automatic boot assessment (or boot-counting) is a feature of `systemd-boot` that allows for automatically detecting invalid boot entries.

When the feature is active, each boot entry has an associated counter with a user defined number of trials. Whenever `systemd-boot` boots an entry, its counter is decreased by one, ultimately being marked as *bad* if the counter ever reaches zero. However, if an entry is successfully booted, systemd will permanently mark it as *good* and remove the counter altogether. Whenever an entry is marked as *bad*, it is sorted last in the `systemd-boot` menu.

A complete explanation of how that feature works can be found [here](https://systemd.io/AUTOMATIC_BOOT_ASSESSMENT/).

## Enabling the feature {#sec-automatic-boot-assessment-enable}

The feature can be enabled by toogling the [boot.loader.systemd-boot.bootCounting](#opt-boot.loader.systemd-boot.bootCounting.enable) option.

## The boot-complete.target unit {#sec-automatic-boot-assessment-boot-complete-target}

A *successful boot* for an entry is defined in terms of the `boot-complete.target` synchronisation point. It is up to the user to schedule all necessary units for the machine to be considered successfully booted before that synchronisation point.

For example, if you are running `docker` on a machine and you want to be sure that a *good* entry is an entry where docker is started successfully.

A configuration for that NixOS machine could look like that:

```

boot.loader.systemd-boot.bootCounting.enable = true;

services.docker.enable = true;

systemd.services.docker = {

  before = [ "boot-complete.target" ];

  wantedBy = [ "boot-complete.target" ];

  unitConfig.FailureAction = "reboot";

};

```

The systemd service type must be of type `notify` or `oneshot` for systemd to dectect the startup error properly.

## Interaction with specialisations {#sec-automatic-boot-assessment-specialisations}

When the boot-counting feature is enabled, `systemd-boot` will still try the boot entries in the same order as they are displayed in the boot menu. This means that the specialisations of a given generation will be tried directly after that generation, but that behavior is customizable with the [boot.loader.systemd-boot.sortKey](#opt-boot.loader.systemd-boot.sortKey) option.

## Limitations {#sec-automatic-boot-assessment-limitations}

This feature has to be used wisely to not risk any data integrity issues. Rollbacking into past generations can sometimes be dangerous, for example if some of the services may have undefined behaviors in the presence of unrecognized data migrations from future versions of themselves.

import sys

import warnings

import json

from typing import NamedTuple, Any, Type

from typing import NamedTuple, Any

from dataclasses import dataclass

from pathlib import Path

# These values will be replaced with actual values during the package build

EFI_SYS_MOUNT_POINT = "@efiSysMountPoint@"

GRACEFUL = "@graceful@"

COPY_EXTRA_FILES = "@copyExtraFiles@"

CHECK_MOUNTPOINTS = "@checkMountpoints@"

BOOT_COUNTING_TRIES = "@bootCountingTries@"

BOOT_COUNTING = "@bootCounting@" == "True"

@dataclass

class BootSpec:

    devicetree: str | None = None  # noqa: N815

    initrdSecrets: str | None = None  # noqa: N815

@dataclass

class Entry:

    profile: str | None

    generation_number: int

    specialisation: str | None

    @classmethod

    def from_path(cls: Type["Entry"], path: Path) -> "Entry":

        filename = path.name

        # Matching nixos-$profile-generation-*.conf

        rex_profile = re.compile(r"^nixos-(.*)-generation-.*\.conf$")

        # Matching nixos*-generation-$number*.conf

        rex_generation = re.compile(r"^nixos.*-generation-([0-9]+).*\.conf$")

        # Matching nixos*-generation-$number-specialisation-$specialisation_name*.conf

        rex_specialisation = re.compile(r"^nixos.*-generation-([0-9]+)-specialisation-([a-zA-Z0-9_]+).*\.conf$")

        profile = rex_profile.sub(r"\1", filename) if rex_profile.match(filename) else None

        specialisation = rex_specialisation.sub(r"\2", filename) if rex_specialisation.match(filename) else None

        try:

            generation_number = int(rex_generation.sub(r"\1", filename))

        except ValueError:

            raise

        return cls(profile, generation_number, specialisation)

@dataclass

class DiskEntry:

    entry: Entry

    default: bool

    counters: str | None

    title: str | None

    description: str | None

    kernel: str

    initrd: str

    kernel_params: str | None

    machine_id: str | None

    sort_key: str

    devicetree: str | None

    @classmethod

    def from_path(cls: Type["DiskEntry"], path: Path) -> "DiskEntry":

        entry = Entry.from_path(path)

        data = path.read_text().splitlines()

        if '' in data:

            data.remove('')

        entry_map = dict(lines.split(' ', 1) for lines in data)

        assert "linux" in entry_map

        assert "initrd" in entry_map

        filename = path.name

        # Matching nixos*-generation-*$counters.conf

        rex_counters = re.compile(r"^nixos.*-generation-.*(\+\d(-\d)?)\.conf$")

        counters = rex_counters.sub(r"\1", filename) if rex_counters.match(filename) else None

        disk_entry = cls(

            entry=entry,

            default=(entry_map.get("sort-key") == "default"),

            counters=counters,

            title=entry_map.get("title"),

            description=entry_map.get("version"),

            kernel=entry_map["linux"],

            initrd=entry_map["initrd"],

            kernel_params=entry_map.get("options"),

            machine_id=entry_map.get("machine-id"),

            sort_key=entry_map.get("sort_key", "nixos"),

            devicetree=entry_map.get("devicetree"),

        )

        return disk_entry

    def write(self, sorted_first: str) -> None:

        # Compute a sort-key sorted before sorted_first

        # This will compute something like: nixos -> nixor-default to make sure we come before other nixos entries,

        # while allowing users users can pre-pend their own entries before.

        default_sort_key = sorted_first[:-1] + chr(ord(sorted_first[-1])-1) + "-default"

        tmp_path = self.path.with_suffix(".tmp")

        with tmp_path.open('w') as f:

            # We use "sort-key" to sort the default generation first.

            # The "default" string is sorted before "non-default" (alphabetically)

            boot_entry = [

                f"title {self.title}" if self.title is not None else None,

                f"version {self.description}" if self.description is not None else None,

                f"linux {self.kernel}",

                f"initrd  {self.initrd}",

                f"options {self.kernel_params}" if self.kernel_params is not None else None,

                f"machine-id {self.machine_id}" if self.machine_id is not None else None,

                f"sort-key {default_sort_key if self.default else self.sort_key}",

                f"devicetree {self.devicetree}" if self.devicetree is not None else None,

            ]

            f.write("\n".join(filter(None, boot_entry)))

            f.flush()

            os.fsync(f.fileno())

        tmp_path.rename(self.path)

    @property

    def path(self) -> Path:

        pieces = [

            "nixos",

            self.entry.profile or None,

            "generation",

            str(self.entry.generation_number),

            f"specialisation-{self.entry.specialisation}" if self.entry.specialisation else None,

        ]

        prefix = "-".join(p for p in pieces if p)

        return Path(f"{BOOT_MOUNT_POINT}/loader/entries/{prefix}{self.counters if self.counters else ''}.conf")

libc = ctypes.CDLL("libc.so.6")

    else:

        return d

def write_loader_conf(profile: str | None) -> None:

    with open(f"{EFI_SYS_MOUNT_POINT}/loader/loader.conf.tmp", 'w') as f:

BOOT_ENTRY = """title {title}

sort-key {sort_key}

version Generation {generation} {description}

linux {kernel}

initrd {initrd}

options {kernel_params}

"""

def generation_conf_filename(profile: str | None, generation: int, specialisation: str | None) -> str:

    pieces = [

        "nixos",

        profile or None,

        "generation",

        str(generation),

        f"specialisation-{specialisation}" if specialisation else None,

    ]

    return "-".join(p for p in pieces if p) + ".conf"

def write_loader_conf(profile: str | None, generation: int, specialisation: str | None) -> None:

    with open(f"{LOADER_CONF}.tmp", 'w') as f:

        f.write(f"timeout {TIMEOUT}\n")

        if profile:

            f.write("default nixos-%s-generation-*\n" % profile)

        else:

            f.write("default nixos-generation-*\n")

        f.write("default %s\n" % generation_conf_filename(profile, generation, specialisation))

        if not EDITOR:

            f.write("editor 0\n")

        if REBOOT_FOR_BITLOCKER:

        os.fsync(f.fileno())

    os.rename(f"{LOADER_CONF}.tmp", LOADER_CONF)

def scan_entries() -> list[DiskEntry]:

    """

    Scan all entries in $ESP/loader/entries/*

    Does not support Type 2 entries as we do not support them for now.

    Returns a generator of Entry.

    """

    entries = []

    for path in Path(f"{EFI_SYS_MOUNT_POINT}/loader/entries/").glob("nixos*-generation-[1-9]*.conf"):

        try:

            entries.append(DiskEntry.from_path(path))

        except ValueError:

            continue

    return entries

def get_bootspec(profile: str | None, generation: int) -> BootSpec:

    system_directory = system_dir(profile, generation, None)

        copy_if_not_exists(store_file_path, f"{BOOT_MOUNT_POINT}{efi_file_path}")

    return efi_file_path

def write_entry(profile: str | None,

                generation: int,

                specialisation: str | None,

                machine_id: str,

                bootspec: BootSpec,

                entries: list[DiskEntry],

                sorted_first: str,

                current: bool) -> None:

def write_entry(profile: str | None, generation: int, specialisation: str | None,

                machine_id: str, bootspec: BootSpec, current: bool) -> None:

    if specialisation:

        bootspec = bootspec.specialisations[specialisation]

    kernel = copy_from_file(bootspec.kernel)

                  f'for "{title} - Configuration {generation}", an older generation', file=sys.stderr)

            print("note: this is normal after having removed "

                  "or renamed a file in `boot.initrd.secrets`", file=sys.stderr)

    entry_file = f"{BOOT_MOUNT_POINT}/loader/entries/%s" % (

        generation_conf_filename(profile, generation, specialisation))

    tmp_path = "%s.tmp" % (entry_file)

    kernel_params = "init=%s " % bootspec.init

    kernel_params = kernel_params + " ".join(bootspec.kernelParams)

    build_time = int(os.path.getctime(system_dir(profile, generation, specialisation)))

    build_date = datetime.datetime.fromtimestamp(build_time).strftime('%F')

    counters = f"+{BOOT_COUNTING_TRIES}" if BOOT_COUNTING else ""

    entry = Entry(profile, generation, specialisation)

    # We check if the entry we are writing is already on disk

    # and we update its "default entry" status

    for entry_on_disk in entries:

        if entry == entry_on_disk.entry:

            entry_on_disk.default = current

            entry_on_disk.write(sorted_first)

            return

    DiskEntry(

        entry=entry,

        title=title,

    with open(tmp_path, 'w') as f:

        f.write(BOOT_ENTRY.format(title=title,

                    sort_key=bootspec.sortKey,

                    generation=generation,

                    kernel=kernel,

                    initrd=initrd,

        counters=counters,

                    kernel_params=kernel_params,

        machine_id=machine_id,

        description=f"Generation {generation} {bootspec.label}, built on {build_date}",

        sort_key=bootspec.sortKey,

        devicetree=devicetree,

        default=current

    ).write(sorted_first)

                    description=f"{bootspec.label}, built on {build_date}"))

        if machine_id is not None:

            f.write("machine-id %s\n" % machine_id)

        if devicetree is not None:

            f.write("devicetree %s\n" % devicetree)

        f.flush()

        os.fsync(f.fileno())

    os.rename(tmp_path, entry_file)

def get_generations(profile: str | None = None) -> list[SystemIdentifier]:

    gen_list = run(

    return configurations[-configurationLimit:]

def remove_old_entries(gens: list[SystemIdentifier], disk_entries: list[DiskEntry]) -> None:

def remove_old_entries(gens: list[SystemIdentifier]) -> None:

    rex_profile = re.compile(r"^" + re.escape(BOOT_MOUNT_POINT) + r"/loader/entries/nixos-(.*)-generation-.*\.conf$")

    rex_generation = re.compile(r"^" + re.escape(BOOT_MOUNT_POINT) + r"/loader/entries/nixos.*-generation-([0-9]+)(-specialisation-.*)?\.conf$")

    known_paths = []

    for gen in gens:

        bootspec = get_bootspec(gen.profile, gen.generation)

        known_paths.append(copy_from_file(bootspec.kernel, True))

        known_paths.append(copy_from_file(bootspec.initrd, True))

    for disk_entry in disk_entries:

        if (disk_entry.entry.profile, disk_entry.entry.generation_number, None) not in gens:

            os.unlink(disk_entry.path)

    for path in glob.iglob(f"{EFI_SYS_MOUNT_POINT}/efi/nixos/*"):

    for path in glob.iglob(f"{BOOT_MOUNT_POINT}/loader/entries/nixos*-generation-[1-9]*.conf"):

        if rex_profile.match(path):

            prof = rex_profile.sub(r"\1", path)

        else:

            prof = None

        try:

            gen_number = int(rex_generation.sub(r"\1", path))

        except ValueError:

            continue

        if (prof, gen_number, None) not in gens:

            os.unlink(path)

    for path in glob.iglob(f"{BOOT_MOUNT_POINT}/{NIXOS_DIR}/*"):

        if path not in known_paths and not os.path.isdir(path):

            os.unlink(path)

def cleanup_esp() -> None:

    for path in glob.iglob(f"{EFI_SYS_MOUNT_POINT}/loader/entries/nixos*"):

        os.unlink(path)

def install_bootloader(args: argparse.Namespace) -> None:

    try:

        with open("/etc/machine-id") as machine_file:

            machine_id = machine_file.readlines()[0].strip()

            machine_id = machine_file.readlines()[0]

    except IOError as e:

        if e.errno != errno.ENOENT:

            raise

    gens = get_generations()

    for profile in get_profiles():

        gens += get_generations(profile)

    entries = scan_entries()

    remove_old_entries(gens, entries)

    # Compute the sort-key that will be sorted first.

    sorted_first = ""

    for gen in gens:

        try:

            bootspec = get_bootspec(gen.profile, gen.generation)

            if bootspec.sortKey < sorted_first or sorted_first == "":

                sorted_first = bootspec.sortKey

        except OSError as e:

            # See https://github.com/NixOS/nixpkgs/issues/114552

            if e.errno == errno.EINVAL:

                profile = f"profile '{gen.profile}'" if gen.profile else "default profile"

                print("ignoring {} in the list of boot entries because of the following error:\n{}".format(profile, e), file=sys.stderr)

            else:

                raise e

    remove_old_entries(gens)

    for gen in gens:

        try:

            bootspec = get_bootspec(gen.profile, gen.generation)

            is_default = os.path.dirname(bootspec.init) == args.default_config

            write_entry(*gen, machine_id, bootspec, entries, sorted_first, current=is_default)

            write_entry(*gen, machine_id, bootspec, current=is_default)

            for specialisation in bootspec.specialisations.keys():

                write_entry(gen.profile, gen.generation, specialisation, machine_id, bootspec, entries, sorted_first, current=(is_default and bootspec.specialisations[specialisation].sortKey == bootspec.sortKey))

                write_entry(gen.profile, gen.generation, specialisation, machine_id, bootspec, current=is_default)

            if is_default:

                write_loader_conf(gen.profile)

                write_loader_conf(*gen)

        except OSError as e:

            # See https://github.com/NixOS/nixpkgs/issues/114552

            if e.errno == errno.EINVAL:

        ${pkgs.coreutils}/bin/install -D $empty_file "${bootMountPoint}/${nixosDir}/.extra-files/loader/entries/"${escapeShellArg n}

      '') cfg.extraEntries)}

    '';

    bootCountingTries = cfg.bootCounting.tries;

    bootCounting = if cfg.bootCounting.enable then "True" else "False";

  };

  finalSystemdBootBuilder = pkgs.writeScript "install-systemd-boot.sh" ''

  '';

in {

  meta = {

    maintainers = with lib.maintainers; [ julienmalka ];

    doc = ./boot-counting.md;

  };

  meta.maintainers = with lib.maintainers; [ julienmalka ];

  imports =

    [ (mkRenamedOptionModule [ "boot" "loader" "gummiboot" "enable" ] [ "boot" "loader" "systemd-boot" "enable" ])

      '';

    };

    bootCounting = {

      enable = mkEnableOption "automatic boot assessment";

      tries = mkOption {

        default = 3;

        type = types.int;

        description = "number of tries each entry should start with";

      };

    };

    rebootForBitlocker = mkOption {

      default = false;