nixpkgs/nixos/modules/profiles/clone-config.nix

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{ config, lib, pkgs, modules, ... }:
with lib;
let
# Location of the repository on the harddrive
nixosPath = toString ../..;
# Check if the path is from the NixOS repository
isNixOSFile = path:
let s = toString path; in
removePrefix nixosPath s != s;
# Copy modules given as extra configuration files. Unfortunately, we
# cannot serialized attribute set given in the list of modules (that's why
# you should use files).
moduleFiles =
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# FIXME: use typeOf (Nix 1.6.1).
filter (x: !isAttrs x && !builtins.isFunction x) modules;
# Partition module files because between NixOS and non-NixOS files. NixOS
# files may change if the repository is updated.
partitionedModuleFiles =
let p = partition isNixOSFile moduleFiles; in
{ nixos = p.right; others = p.wrong; };
# Path transformed to be valid on the installation device. Thus the
# device configuration could be rebuild.
relocatedModuleFiles =
let
relocateNixOS = path:
"<nixpkgs/nixos" + removePrefix nixosPath (toString path) + ">";
relocateOthers = null;
in
{ nixos = map relocateNixOS partitionedModuleFiles.nixos;
others = []; # TODO: copy the modules to the install-device repository.
};
# A dummy /etc/nixos/configuration.nix in the booted CD that
# rebuilds the CD's configuration (and allows the configuration to
# be modified, of course, providing a true live CD). Problem is
# that we don't really know how the CD was built - the Nix
# expression language doesn't allow us to query the expression being
# evaluated. So we'll just hope for the best.
configClone = pkgs.writeText "configuration.nix"
''
{ config, pkgs, ... }:
{
imports = [ ${toString config.installer.cloneConfigIncludes} ];
}
'';
in
{
options = {
installer.cloneConfig = mkOption {
default = true;
description = ''
Try to clone the installation-device configuration by re-using it's
profile from the list of imported modules.
'';
};
installer.cloneConfigIncludes = mkOption {
default = [];
example = [ "./nixos/modules/hardware/network/rt73.nix" ];
description = ''
List of modules used to re-build this installation device profile.
'';
};
};
config = {
installer.cloneConfigIncludes =
relocatedModuleFiles.nixos ++ relocatedModuleFiles.others;
boot.postBootCommands =
''
# Provide a mount point for nixos-install.
mkdir -p /mnt
${optionalString config.installer.cloneConfig ''
# Provide a configuration for the CD/DVD itself, to allow users
# to run nixos-rebuild to change the configuration of the
# running system on the CD/DVD.
if ! [ -e /etc/nixos/configuration.nix ]; then
cp ${configClone} /etc/nixos/configuration.nix
fi
''}
'';
};
}