nixpkgs/nixos/modules/misc/version.nix
Eelco Dolstra d166c854b6 Add option system.stateVersion
This option requests compatibility with older NixOS releases with
respect to stateful data, in cases where new releases have defaults
that might be incompatible with system state of existing NixOS
deployments. For instance, if we change the default version of
PostgreSQL, existing deployments will break if the new version can't
read databases created by the old version.

So for example, setting

  system.stateVersion = "15.07";

requests that options like services.postgresql.package use defaults
corresponding to the 15.07 release branch. Note that
nixos-generate-config emits this option. (In the future, NixOps may
set system.stateVersion to the NixOS release in use when the machine
was created.)

See also #7939 for another motivating example.
2015-07-27 20:30:09 +02:00

96 lines
2.7 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
{
options = {
system.stateVersion = mkOption {
type = types.str;
default = config.system.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).
'';
};
system.nixosVersion = mkOption {
internal = true;
type = types.str;
description = "NixOS version.";
};
system.nixosRelease = mkOption {
internal = true;
type = types.str;
default = readFile "${toString pkgs.path}/.version";
description = "NixOS release.";
};
system.nixosVersionSuffix = mkOption {
internal = true;
type = types.str;
description = "NixOS version suffix.";
};
system.nixosRevision = mkOption {
internal = true;
type = types.str;
description = "NixOS Git revision hash.";
};
system.nixosCodeName = mkOption {
internal = true;
type = types.str;
description = "NixOS release code name.";
};
system.defaultChannel = mkOption {
internal = true;
type = types.str;
default = https://nixos.org/channels/nixos-unstable;
description = "Default NixOS channel to which the root user is subscribed.";
};
};
config = {
system.nixosVersion = mkDefault (config.system.nixosRelease + config.system.nixosVersionSuffix);
system.nixosVersionSuffix =
let suffixFile = "${toString pkgs.path}/.version-suffix"; in
mkDefault (if pathExists suffixFile then readFile suffixFile else "pre-git");
system.nixosRevision =
let fn = "${toString pkgs.path}/.git-revision"; in
mkDefault (if pathExists fn then readFile fn else "master");
# Note: code names must only increase in alphabetical order.
system.nixosCodeName = "Dingo";
# Generate /etc/os-release. See
# http://0pointer.de/public/systemd-man/os-release.html for the
# format.
environment.etc."os-release".text =
''
NAME=NixOS
ID=nixos
VERSION="${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/"
'';
};
}