nixpkgs/nixos/modules/misc/version.nix
pennae fc614c37c6 nixos/documentation: split options doc build
most modules can be evaluated for their documentation in a very
restricted environment that doesn't include all of nixpkgs. this
evaluation can then be cached and reused for subsequent builds, merging
only documentation that has changed into the cached set. since nixos
ships with a large number of modules of which only a few are used in any
given config this can save evaluation a huge percentage of nixos
options available in any given config.

in tests of this caching, despite having to copy most of nixos/, saves
about 80% of the time needed to build the system manual, or about two
second on the machine used for testing. build time for a full system
config shrank from 9.4s to 7.4s, while turning documentation off
entirely shortened the build to 7.1s.
2022-01-02 19:46:13 +01:00

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{ config, lib, options, pkgs, ... }:
with lib;
let
cfg = config.system.nixos;
opt = options.system.nixos;
in
{
imports = [
(mkRenamedOptionModule [ "system" "nixosVersion" ] [ "system" "nixos" "version" ])
(mkRenamedOptionModule [ "system" "nixosVersionSuffix" ] [ "system" "nixos" "versionSuffix" ])
(mkRenamedOptionModule [ "system" "nixosRevision" ] [ "system" "nixos" "revision" ])
(mkRenamedOptionModule [ "system" "nixosLabel" ] [ "system" "nixos" "label" ])
];
options.system = {
nixos.version = mkOption {
internal = true;
type = types.str;
description = "The full NixOS version (e.g. <literal>16.03.1160.f2d4ee1</literal>).";
};
nixos.release = mkOption {
readOnly = true;
type = types.str;
default = trivial.release;
description = "The NixOS release (e.g. <literal>16.03</literal>).";
};
nixos.versionSuffix = mkOption {
internal = true;
type = types.str;
default = trivial.versionSuffix;
description = "The NixOS version suffix (e.g. <literal>1160.f2d4ee1</literal>).";
};
nixos.revision = mkOption {
internal = true;
type = types.nullOr types.str;
default = trivial.revisionWithDefault null;
description = "The Git revision from which this NixOS configuration was built.";
};
nixos.codeName = mkOption {
readOnly = true;
type = types.str;
default = trivial.codeName;
description = "The NixOS release code name (e.g. <literal>Emu</literal>).";
};
stateVersion = mkOption {
type = types.str;
default = cfg.release;
defaultText = literalExpression "config.${opt.release}";
description = ''
Every once in a while, a new NixOS release may change
configuration defaults in a way incompatible with stateful
data. For instance, if the default version of PostgreSQL
changes, the new version will probably be unable to read your
existing databases. To prevent such breakage, you should set the
value of this option to the NixOS release with which you want
to be compatible. The effect is that NixOS will use
defaults corresponding to the specified release (such as using
an older version of PostgreSQL).
Its perfectly fine and recommended to leave this value at the
release version of the first install of this system.
Changing this option will not upgrade your system. In fact it
is meant to stay constant exactly when you upgrade your system.
You should only bump this option, if you are sure that you can
or have migrated all state on your system which is affected
by this option.
'';
};
defaultChannel = mkOption {
internal = true;
type = types.str;
default = "https://nixos.org/channels/nixos-unstable";
description = "Default NixOS channel to which the root user is subscribed.";
};
configurationRevision = mkOption {
type = types.nullOr types.str;
default = null;
description = "The Git revision of the top-level flake from which this configuration was built.";
};
};
config = {
system.nixos = {
# These defaults are set here rather than up there so that
# changing them would not rebuild the manual
version = mkDefault (cfg.release + cfg.versionSuffix);
};
# Generate /etc/os-release. See
# https://www.freedesktop.org/software/systemd/man/os-release.html for the
# format.
environment.etc.os-release.text =
''
NAME=NixOS
ID=nixos
VERSION="${cfg.release} (${cfg.codeName})"
VERSION_CODENAME=${toLower cfg.codeName}
VERSION_ID="${cfg.release}"
BUILD_ID="${cfg.version}"
PRETTY_NAME="NixOS ${cfg.release} (${cfg.codeName})"
LOGO="nix-snowflake"
HOME_URL="https://nixos.org/"
DOCUMENTATION_URL="https://nixos.org/learn.html"
SUPPORT_URL="https://nixos.org/community.html"
BUG_REPORT_URL="https://github.com/NixOS/nixpkgs/issues"
'';
};
# uses version info nixpkgs, which requires a full nixpkgs path
meta.buildDocsInSandbox = false;
}