436 lines
		
	
	
		
			15 KiB
		
	
	
	
		
			Nix
		
	
	
	
	
	
			
		
		
	
	
			436 lines
		
	
	
		
			15 KiB
		
	
	
	
		
			Nix
		
	
	
	
	
	
{ config, lib, pkgs, ... }:
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with lib;
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let
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  cfg = config.nix;
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  nix = cfg.package;
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  makeNixBuildUser = nr:
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    { name = "nixbld${toString nr}";
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      description = "Nix build user ${toString nr}";
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      /* For consistency with the setgid(2), setuid(2), and setgroups(2)
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         calls in `libstore/build.cc', don't add any supplementary group
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         here except "nixbld".  */
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      uid = builtins.add config.ids.uids.nixbld nr;
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      group = "nixbld";
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      extraGroups = [ "nixbld" ];
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    };
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  nixbldUsers = map makeNixBuildUser (range 1 cfg.nrBuildUsers);
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  nixConf =
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    let
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      # If we're using a chroot for builds, then provide /bin/sh in
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      # the chroot as a bind-mount to bash. This means we also need to
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      # include the entire closure of bash.
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      sh = pkgs.stdenv.shell;
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      binshDeps = pkgs.writeReferencesToFile sh;
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    in
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      pkgs.runCommand "nix.conf" {extraOptions = cfg.extraOptions; } ''
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        extraPaths=$(for i in $(cat ${binshDeps}); do if test -d $i; then echo $i; fi; done)
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        cat > $out <<END
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        # WARNING: this file is generated from the nix.* options in
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        # your NixOS configuration, typically
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        # /etc/nixos/configuration.nix.  Do not edit it!
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        build-users-group = nixbld
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        build-max-jobs = ${toString (cfg.maxJobs)}
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        build-cores = ${toString (cfg.buildCores)}
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        build-use-chroot = ${if cfg.useChroot then "true" else "false"}
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        build-chroot-dirs = ${toString cfg.chrootDirs} /bin/sh=${sh} $(echo $extraPaths)
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        binary-caches = ${toString cfg.binaryCaches}
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        trusted-binary-caches = ${toString cfg.trustedBinaryCaches}
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        binary-cache-public-keys = ${toString cfg.binaryCachePublicKeys}
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        ${optionalString cfg.requireSignedBinaryCaches ''
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          signed-binary-caches = *
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        ''}
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        trusted-users = ${toString cfg.trustedUsers}
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        allowed-users = ${toString cfg.allowedUsers}
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        $extraOptions
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        END
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      '';
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in
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{
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  ###### interface
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  options = {
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    nix = {
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      package = mkOption {
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        type = types.package;
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        default = pkgs.nix;
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        defaultText = "pkgs.nix";
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        description = ''
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          This option specifies the Nix package instance to use throughout the system.
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        '';
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      };
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      maxJobs = mkOption {
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        type = types.int;
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        default = 1;
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        example = 64;
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        description = ''
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          This option defines the maximum number of jobs that Nix will try
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          to build in parallel.  The default is 1.  You should generally
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          set it to the total number of logical cores in your system (e.g., 16
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          for two CPUs with 4 cores each and hyper-threading).
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        '';
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      };
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      buildCores = mkOption {
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        type = types.int;
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        default = 1;
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        example = 64;
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        description = ''
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          This option defines the maximum number of concurrent tasks during
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          one build. It affects, e.g., -j option for make. The default is 1.
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          The special value 0 means that the builder should use all
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          available CPU cores in the system. Some builds may become
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          non-deterministic with this option; use with care! Packages will
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          only be affected if enableParallelBuilding is set for them.
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        '';
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      };
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      useChroot = mkOption {
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        type = types.bool;
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        default = false;
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        description = "
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          If set, Nix will perform builds in a chroot-environment that it
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          will set up automatically for each build.  This prevents
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          impurities in builds by disallowing access to dependencies
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          outside of the Nix store.
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        ";
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      };
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      chrootDirs = mkOption {
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        type = types.listOf types.str;
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        default = [];
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        example = [ "/dev" "/proc" ];
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        description =
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          ''
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            Directories from the host filesystem to be included
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            in the chroot.
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          '';
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      };
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      extraOptions = mkOption {
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        type = types.lines;
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        default = "";
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        example = ''
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          gc-keep-outputs = true
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          gc-keep-derivations = true
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        '';
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        description = "Additional text appended to <filename>nix.conf</filename>.";
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      };
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      distributedBuilds = mkOption {
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        type = types.bool;
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        default = false;
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        description = ''
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          Whether to distribute builds to the machines listed in
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          <option>nix.buildMachines</option>.
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        '';
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      };
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      daemonNiceLevel = mkOption {
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        type = types.int;
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        default = 0;
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        description = ''
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          Nix daemon process priority. This priority propagates to build processes.
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          0 is the default Unix process priority, 19 is the lowest.
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        '';
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      };
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      daemonIONiceLevel = mkOption {
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        type = types.int;
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        default = 0;
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        description = ''
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          Nix daemon process I/O priority. This priority propagates to build processes.
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          0 is the default Unix process I/O priority, 7 is the lowest.
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        '';
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      };
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      buildMachines = mkOption {
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        type = types.listOf types.attrs;
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        default = [];
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        example = [
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          { hostName = "voila.labs.cs.uu.nl";
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            sshUser = "nix";
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            sshKey = "/root/.ssh/id_buildfarm";
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            system = "powerpc-darwin";
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            maxJobs = 1;
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          }
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          { hostName = "linux64.example.org";
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            sshUser = "buildfarm";
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            sshKey = "/root/.ssh/id_buildfarm";
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            system = "x86_64-linux";
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            maxJobs = 2;
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            supportedFeatures = "kvm";
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            mandatoryFeatures = "perf";
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          }
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        ];
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        description = ''
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          This option lists the machines to be used if distributed
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          builds are enabled (see
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          <option>nix.distributedBuilds</option>).  Nix will perform
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          derivations on those machines via SSH by copying the inputs
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          to the Nix store on the remote machine, starting the build,
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          then copying the output back to the local Nix store.  Each
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          element of the list should be an attribute set containing
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          the machine's host name (<varname>hostname</varname>), the
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          user name to be used for the SSH connection
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          (<varname>sshUser</varname>), the Nix system type
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          (<varname>system</varname>, e.g.,
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          <literal>"i686-linux"</literal>), the maximum number of
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          jobs to be run in parallel on that machine
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          (<varname>maxJobs</varname>), the path to the SSH private
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          key to be used to connect (<varname>sshKey</varname>), a
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          list of supported features of the machine
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          (<varname>supportedFeatures</varname>) and a list of
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          mandatory features of the machine
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          (<varname>mandatoryFeatures</varname>). The SSH private key
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          should not have a passphrase, and the corresponding public
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          key should be added to
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          <filename>~<replaceable>sshUser</replaceable>/authorized_keys</filename>
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          on the remote machine.
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        '';
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      };
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      # Environment variables for running Nix.
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      envVars = mkOption {
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        type = types.attrs;
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        internal = true;
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        default = {};
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        description = "Environment variables used by Nix.";
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      };
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      nrBuildUsers = mkOption {
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        type = types.int;
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        description = ''
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          Number of <literal>nixbld</literal> user accounts created to
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          perform secure concurrent builds.  If you receive an error
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          message saying that “all build users are currently in use”,
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          you should increase this value.
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        '';
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      };
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      readOnlyStore = mkOption {
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        type = types.bool;
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        default = true;
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        description = ''
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          If set, NixOS will enforce the immutability of the Nix store
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          by making <filename>/nix/store</filename> a read-only bind
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          mount.  Nix will automatically make the store writable when
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          needed.
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        '';
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      };
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      binaryCaches = mkOption {
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        type = types.listOf types.str;
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        default = [ https://cache.nixos.org/ ];
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        description = ''
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          List of binary cache URLs used to obtain pre-built binaries
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          of Nix packages.
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        '';
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      };
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      trustedBinaryCaches = mkOption {
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        type = types.listOf types.str;
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        default = [ ];
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        example = [ http://hydra.nixos.org/ ];
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        description = ''
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          List of binary cache URLs that non-root users can use (in
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          addition to those specified using
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          <option>nix.binaryCaches</option> by passing
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          <literal>--option binary-caches</literal> to Nix commands.
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        '';
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      };
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      requireSignedBinaryCaches = mkOption {
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        type = types.bool;
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        default = true;
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        description = ''
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          If enabled (the default), Nix will only download binaries from binary caches if
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          they are cryptographically signed with any of the keys listed in
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          <option>nix.binaryCachePublicKeys</option>. If disabled, signatures are neither
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          required nor checked, so it's strongly recommended that you use only
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          trustworthy caches and https to prevent man-in-the-middle attacks.
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        '';
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      };
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      binaryCachePublicKeys = mkOption {
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        type = types.listOf types.str;
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        example = [ "hydra.nixos.org-1:CNHJZBh9K4tP3EKF6FkkgeVYsS3ohTl+oS0Qa8bezVs=" ];
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        description = ''
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          List of public keys used to sign binary caches. If
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          <option>nix.requireSignedBinaryCaches</option> is enabled,
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          then Nix will use a binary from a binary cache if and only
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          if it is signed by <emphasis>any</emphasis> of the keys
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          listed here. By default, only the key for
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          <uri>cache.nixos.org</uri> is included.
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        '';
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      };
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      trustedUsers = mkOption {
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        type = types.listOf types.str;
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        default = [ "root" ];
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        example = [ "root" "alice" "@wheel" ];
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        description = ''
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          A list of names of users that have additional rights when
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          connecting to the Nix daemon, such as the ability to specify
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          additional binary caches, or to import unsigned NARs. You
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          can also specify groups by prefixing them with
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          <literal>@</literal>; for instance,
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          <literal>@wheel</literal> means all users in the wheel
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          group.
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        '';
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      };
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      allowedUsers = mkOption {
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        type = types.listOf types.str;
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        default = [ "*" ];
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        example = [ "@wheel" "@builders" "alice" "bob" ];
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        description = ''
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          A list of names of users (separated by whitespace) that are
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          allowed to connect to the Nix daemon. As with
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          <option>nix.trustedUsers</option>, you can specify groups by
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          prefixing them with <literal>@</literal>. Also, you can
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          allow all users by specifying <literal>*</literal>. The
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          default is <literal>*</literal>. Note that trusted users are
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          always allowed to connect.
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        '';
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      };
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      nixPath = mkOption {
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        type = types.listOf types.str;
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        default =
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          [ "/nix/var/nix/profiles/per-user/root/channels/nixos"
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            "nixos-config=/etc/nixos/configuration.nix"
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            "/nix/var/nix/profiles/per-user/root/channels"
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          ];
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        description = ''
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          The default Nix expression search path, used by the Nix
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          evaluator to look up paths enclosed in angle brackets
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          (e.g. <literal><nixpkgs></literal>).
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        '';
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      };
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    };
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  };
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  ###### implementation
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  config = {
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    nix.binaryCachePublicKeys = [ "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=" ];
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    environment.etc."nix/nix.conf".source = nixConf;
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    # List of machines for distributed Nix builds in the format
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    # expected by build-remote.pl.
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    environment.etc."nix/machines" =
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      { enable = cfg.buildMachines != [];
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        text =
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          concatMapStrings (machine:
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            "${if machine ? sshUser then "${machine.sshUser}@" else ""}${machine.hostName} "
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            + machine.system or (concatStringsSep "," machine.systems)
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            + " ${machine.sshKey or "-"} ${toString machine.maxJobs or 1} "
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            + toString (machine.speedFactor or 1)
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            + " "
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            + concatStringsSep "," (machine.mandatoryFeatures or [] ++ machine.supportedFeatures or [])
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            + " "
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            + concatStringsSep "," machine.mandatoryFeatures or []
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            + "\n"
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          ) cfg.buildMachines;
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      };
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    systemd.packages = [ nix ];
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    systemd.sockets.nix-daemon.wantedBy = [ "sockets.target" ];
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    systemd.services.nix-daemon =
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      { path = [ nix pkgs.openssl pkgs.utillinux config.programs.ssh.package ]
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          ++ optionals cfg.distributedBuilds [ pkgs.gzip ];
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        environment = cfg.envVars
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          // { CURL_CA_BUNDLE = "/etc/ssl/certs/ca-certificates.crt"; }
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          // config.networking.proxy.envVars;
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        unitConfig.RequiresMountsFor = "/nix/store";
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        serviceConfig =
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          { Nice = cfg.daemonNiceLevel;
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            IOSchedulingPriority = cfg.daemonIONiceLevel;
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            LimitNOFILE = 4096;
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          };
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        restartTriggers = [ nixConf ];
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      };
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    nix.envVars =
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      { NIX_CONF_DIR = "/etc/nix";
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        # Enable the copy-from-other-stores substituter, which allows
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        # builds to be sped up by copying build results from remote
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        # Nix stores.  To do this, mount the remote file system on a
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        # subdirectory of /run/nix/remote-stores.
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        NIX_OTHER_STORES = "/run/nix/remote-stores/*/nix";
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      }
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      // optionalAttrs cfg.distributedBuilds {
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        NIX_BUILD_HOOK = "${nix}/libexec/nix/build-remote.pl";
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        NIX_REMOTE_SYSTEMS = "/etc/nix/machines";
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        NIX_CURRENT_LOAD = "/run/nix/current-load";
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      };
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    # Set up the environment variables for running Nix.
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    environment.sessionVariables = cfg.envVars //
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      { NIX_PATH = concatStringsSep ":" cfg.nixPath;
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      };
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    environment.extraInit =
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      ''
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        # Set up secure multi-user builds: non-root users build through the
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        # Nix daemon.
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        if [ "$USER" != root -o ! -w /nix/var/nix/db ]; then
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            export NIX_REMOTE=daemon
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        fi
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      '';
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    nix.nrBuildUsers = mkDefault (lib.max 10 cfg.maxJobs);
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    users.extraUsers = nixbldUsers;
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    services.xserver.displayManager.hiddenUsers = map ({ name, ... }: name) nixbldUsers;
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    system.activationScripts.nix = stringAfter [ "etc" "users" ]
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      ''
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        # Nix initialisation.
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        mkdir -m 0755 -p \
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          /nix/var/nix/gcroots \
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          /nix/var/nix/temproots \
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          /nix/var/nix/manifests \
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          /nix/var/nix/userpool \
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          /nix/var/nix/profiles \
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          /nix/var/nix/db \
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          /nix/var/log/nix/drvs \
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          /nix/var/nix/channel-cache
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        mkdir -m 1777 -p \
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          /nix/var/nix/gcroots/per-user \
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          /nix/var/nix/profiles/per-user \
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          /nix/var/nix/gcroots/tmp
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      '';
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  };
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}
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