Add a way to pin a NixOS version within the module system.

This modification add a way to re-evaluate the module system with a
different version of NixOS, or with a different set of arguments.
This commit is contained in:
Nicolas B. Pierron 2015-11-18 00:26:00 +00:00
parent bd33a41493
commit a5992ad61b
9 changed files with 259 additions and 4 deletions

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@ -1,12 +1,20 @@
{ configuration ? import ./lib/from-env.nix "NIXOS_CONFIG" <nixos-config>
, system ? builtins.currentSystem
, extraModules ? []
# This attribute is used to specify a different nixos version, a different
# system or additional modules which might be set conditionally.
, reEnter ? false
}:
let
reEnterModule = {
config.nixos.path = with (import ../lib); mkIf reEnter (mkForce null);
config.nixos.configuration = configuration;
};
eval = import ./lib/eval-config.nix {
inherit system;
modules = [ configuration ];
modules = [ configuration reEnterModule ] ++ extraModules;
};
inherit (eval) pkgs;
@ -14,14 +22,14 @@ let
# This is for `nixos-rebuild build-vm'.
vmConfig = (import ./lib/eval-config.nix {
inherit system;
modules = [ configuration ./modules/virtualisation/qemu-vm.nix ];
modules = [ configuration reEnterModule ./modules/virtualisation/qemu-vm.nix ] ++ extraModules;
}).config;
# This is for `nixos-rebuild build-vm-with-bootloader'.
vmWithBootLoaderConfig = (import ./lib/eval-config.nix {
inherit system;
modules =
[ configuration
[ configuration reEnterModule
./modules/virtualisation/qemu-vm.nix
{ virtualisation.useBootLoader = true; }
];
@ -30,7 +38,7 @@ let
in
{
inherit (eval) config options;
inherit (eval.config.nixos.reflect) config options;
system = eval.config.system.build.toplevel;

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@ -26,6 +26,7 @@ effect after you run <command>nixos-rebuild</command>.</para>
<!-- FIXME: auto-include NixOS module docs -->
<xi:include href="postgresql.xml" />
<xi:include href="nixos.xml" />
<!-- Apache; libvirtd virtualisation -->

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@ -55,6 +55,7 @@ let
cp -prd $sources/* . # */
chmod -R u+w .
cp ${../../modules/services/databases/postgresql.xml} configuration/postgresql.xml
cp ${../../modules/misc/nixos.xml} configuration/nixos.xml
ln -s ${optionsDocBook} options-db.xml
echo "${version}" > version
'';

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@ -6,6 +6,26 @@
<title>Unstable</title>
<para>In addition to numerous new and upgraded packages, this release
has the following highlights:</para>
<itemizedlist>
<listitem>
<para>You can now pin a specific version of NixOS in your <filename>configuration.nix</filename>
by setting:
<programlisting>
nixos.path = ./nixpkgs-unstable-2015-12-06/nixos;
</programlisting>
This will make NixOS re-evaluate your configuration with the modules of
the specified NixOS version at the given path. For more details, see
<xref linkend="module-misc-nixos" /></para>
</listitem>
</itemizedlist>
<para>When upgrading from a previous release, please be aware of the
following incompatible changes:</para>

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@ -0,0 +1,82 @@
{ config, options, lib, ... }:
# This modules is used to inject a different NixOS version as well as its
# argument such that one can pin a specific version with the versionning
# system of the configuration.
let
nixosReentry = import config.nixos.path {
inherit (config.nixos) configuration extraModules;
inherit (config.nixpkgs) system;
reEnter = true;
};
in
with lib;
{
options = {
nixos.path = mkOption {
default = null;
example = literalExample "./nixpkgs-15.09/nixos";
type = types.nullOr types.path;
description = ''
This option give the ability to evaluate the current set of modules
with a different version of NixOS. This option can be used version
the version of NixOS with the configuration without relying on the
<literal>NIX_PATH</literal> environment variable.
'';
};
nixos.system = mkOption {
example = "i686-linux";
type = types.uniq types.str;
description = ''
Name of the system used to compile NixOS.
'';
};
nixos.extraModules = mkOption {
default = [];
example = literalExample "mkIf config.services.openssh.enable [ ./sshd-config.nix ]";
type = types.listOf types.unspecified;
description = ''
Define additional modules which would be loaded to evaluate the
configuration.
'';
};
nixos.configuration = mkOption {
type = types.unspecified;
internal = true;
description = ''
Option used by <filename>nixos/default.nix</filename> to re-inject
the same configuration module as the one used for the current
execution.
'';
};
nixos.reflect = mkOption {
default = { inherit config options; };
type = types.unspecified;
internal = true;
description = ''
Provides <literal>config</literal> and <literal>options</literal>
computed by the module system and given as argument to all
modules. These are used for introspection of options and
configuration by tools such as <literal>nixos-option</literal>.
'';
};
};
config = mkMerge [
(mkIf (config.nixos.path != null) (mkForce {
system.build.toplevel = nixosReentry.system;
system.build.vm = nixosReentry.vm;
nixos.reflect = { inherit (nixosReentry) config options; };
}))
{ meta.maintainers = singleton lib.maintainers.pierron;
meta.doc = ./nixos.xml;
}
];
}

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@ -0,0 +1,84 @@
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:xi="http://www.w3.org/2001/XInclude"
version="5.0"
xml:id="module-misc-nixos">
<title>NixOS Reentry</title>
<!-- FIXME: render nicely -->
<!-- FIXME: source can be added automatically -->
<para><emphasis>Source:</emphasis> <filename>modules/misc/nixos.nix</filename></para>
<!-- FIXME: more stuff, like maintainer? -->
<para>NixOS reentry can be used for both pinning the evaluation to a
specific version of NixOS, and to dynamically add additional modules into
the Module evaluation.</para>
<section><title>NixOS Version Pinning</title>
<para>To pin a specific version of NixOS, you need a version that you can
either clone localy, or that you can fetch remotely.</para>
<para>If you already have a cloned version of NixOS in the directory
<filename>/etc/nixos/nixpkgs-16-03</filename>, then you can specify the
<option>nixos.path</option> with either the path or the relative path of
your NixOS clone. For example, you can add the following to your
<filename>/etc/nixos/configuration.nix</filename> file:
<programlisting>
nixos.path = ./nixpkgs-16-03/nixos;
</programlisting>
</para>
<para>Another option is to fetch a specific version of NixOS, with either
the <literal>fetchTarball</literal> builtin, or the
<literal>pkgs.fetchFromGithub</literal> function and use the result as an
input.
<programlisting>
nixos.path = "${builtins.fetchTarball https://github.com/NixOS/nixpkgs/archive/1f27976e03c15183191d1b4aa1a40d1f14666cd2.tar.gz}/nixos";
</programlisting>
</para>
</section>
<section><title>Adding Module Dynamically</title>
<para>To add additional module, the recommended way is to use statically
known modules in the list of imported arguments as described in <xref
linkend="sec-modularity" />. Unfortunately, this recommended method has
limitation, such that the list of imported files cannot be selected based on
the content of the configuration.
Fortunately, NixOS reentry system can be used as an alternative to register
new imported modules based on the content of the configuration. To do so,
one should define both <option>nixos.path</option> and
<option>nixos.extraModules</option> options.
<programlisting>
nixos.path = &lt;nixos&gt;;
nixos.extraModules =
if config.networking.hostName == "server" then
[ ./server.nix ] else [ ./client.nix ];
</programlisting>
Also note, that the above can be reimplemented in a different way which is
not as expensive, by using <literal>mkIf</literal> at the top each
configuration if both modules are present on the file system (see <xref
linkend="sec-option-definitions" />) and by always inmporting both
modules.</para>
</section>
<section><title>Options</title>
<para>FIXME: auto-generated list of module options.</para>
</section>
</chapter>

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@ -52,6 +52,7 @@
./misc/lib.nix
./misc/locate.nix
./misc/meta.nix
./misc/nixos.nix
./misc/nixpkgs.nix
./misc/passthru.nix
./misc/version.nix

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@ -276,6 +276,7 @@ in rec {
tests.networkingProxy = callTest tests/networking-proxy.nix {};
tests.nfs3 = callTest tests/nfs.nix { version = 3; };
tests.nfs4 = callTest tests/nfs.nix { version = 4; };
tests.nixosPinVersion = callTest tests/nixos-pin-version.nix {};
tests.nsd = callTest tests/nsd.nix {};
tests.openssh = callTest tests/openssh.nix {};
tests.panamax = hydraJob (import tests/panamax.nix { system = "x86_64-linux"; });

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@ -0,0 +1,57 @@
{ system ? builtins.currentSystem }:
with import ../lib/testing.nix { inherit system; };
let
in
pkgs.stdenv.mkDerivation rec {
name = "nixos-pin-version";
src = ../..;
buildInputs = with pkgs; [ nix gnugrep ];
withoutPath = pkgs.writeText "configuration.nix" ''
{
nixos.extraModules = [ ({lib, ...}: { system.nixosRevision = lib.mkForce "ABCDEF"; }) ];
}
'';
withPath = pkgs.writeText "configuration.nix" ''
{
nixos.path = ${src}/nixos ;
nixos.extraModules = [ ({lib, ...}: { system.nixosRevision = lib.mkForce "ABCDEF"; }) ];
}
'';
phases = "buildPhase";
buildPhase = ''
datadir="${pkgs.nix}/share"
export TEST_ROOT=$(pwd)/test-tmp
export NIX_STORE_DIR=$TEST_ROOT/store
export NIX_LOCALSTATE_DIR=$TEST_ROOT/var
export NIX_LOG_DIR=$TEST_ROOT/var/log/nix
export NIX_STATE_DIR=$TEST_ROOT/var/nix
export NIX_DB_DIR=$TEST_ROOT/db
export NIX_CONF_DIR=$TEST_ROOT/etc
export NIX_MANIFESTS_DIR=$TEST_ROOT/var/nix/manifests
export NIX_BUILD_HOOK=
export PAGER=cat
cacheDir=$TEST_ROOT/binary-cache
nix-store --init
export NIX_PATH="nixpkgs=$src:nixos=$src/nixos:nixos-config=${withoutPath}" ;
if test $(nix-instantiate $src/nixos -A config.system.nixosRevision --eval-only) != '"ABCDEF"' ; then :;
else
echo "Unexpected re-entry without the nixos.path option defined.";
exit 1;
fi;
export NIX_PATH="nixpkgs=$src:nixos=$src/nixos:nixos-config=${withPath}" ;
if test $(nix-instantiate $src/nixos -A config.system.nixosRevision --eval-only) = '"ABCDEF"' ; then :;
else
echo "Expected a re-entry when the nixos.path option is defined.";
exit 1;
fi;
touch $out;
'';
}