{ config, lib, pkgs, ... }: with lib; let cfg = config.system; releaseFile = "${toString pkgs.path}/.version"; suffixFile = "${toString pkgs.path}/.version-suffix"; revisionFile = "${toString pkgs.path}/.git-revision"; gitRepo = "${toString pkgs.path}/.git"; gitCommitId = lib.substring 0 7 (commitIdFromGitRepo gitRepo); in { options.system = { stateVersion = mkOption { type = types.str; default = cfg.nixosRelease; 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 can set the value of this option to the NixOS release with which you want to be compatible. The effect is that NixOS will option defaults corresponding to the specified release (such as using an older version of PostgreSQL). ''; }; nixosLabel = mkOption { type = types.str; description = '' NixOS version name to be used in the names of generated outputs and boot labels. If you ever wanted to influence the labels in your GRUB menu, this is option is for you. Can be set directly or with NIXOS_LABEL environment variable for nixos-rebuild, e.g.: #!/bin/sh today=`date +%Y%m%d` branch=`(cd nixpkgs ; git branch 2>/dev/null | sed -n '/^\* / { s|^\* ||; p; }')` revision=`(cd nixpkgs ; git rev-parse HEAD)` export NIXOS_LABEL="$today.$branch-''${revision:0:7}" nixos-rebuild switch ''; }; nixosVersion = mkOption { internal = true; type = types.str; description = "NixOS version."; }; nixosRelease = mkOption { readOnly = true; type = types.str; default = readFile releaseFile; description = "NixOS release."; }; nixosVersionSuffix = mkOption { internal = true; type = types.str; default = if pathExists suffixFile then readFile suffixFile else "pre-git"; description = "NixOS version suffix."; }; nixosRevision = mkOption { internal = true; type = types.str; default = if pathExists revisionFile then readFile revisionFile else "master"; description = "NixOS Git revision hash."; }; nixosCodeName = mkOption { readOnly = true; type = types.str; description = "NixOS release code name."; }; defaultChannel = mkOption { internal = true; type = types.str; default = https://nixos.org/channels/nixos-unstable; description = "Default NixOS channel to which the root user is subscribed."; }; }; config = { system = { # These defaults are set here rather than up there so that # changing them would not rebuild the manual nixosLabel = mkDefault (maybeEnv "NIXOS_LABEL" cfg.nixosVersion); nixosVersion = mkDefault (maybeEnv "NIXOS_VERSION" (cfg.nixosRelease + cfg.nixosVersionSuffix)); nixosRevision = mkIf (pathExists gitRepo) (mkDefault gitCommitId); nixosVersionSuffix = mkIf (pathExists gitRepo) (mkDefault (".git." + gitCommitId)); # Note: code names must only increase in alphabetical order. nixosCodeName = "Flounder"; }; # Generate /etc/os-release. See # http://0pointer.de/public/systemd-man/os-release.html for the # format. environment.etc."os-release".text = '' NAME=NixOS ID=nixos VERSION="${config.system.nixosVersion} (${config.system.nixosCodeName})" VERSION_ID="${config.system.nixosVersion}" PRETTY_NAME="NixOS ${config.system.nixosVersion} (${config.system.nixosCodeName})" HOME_URL="http://nixos.org/" ''; }; }