Using pkgs.lib on the spine of module evaluation is problematic because the pkgs argument depends on the result of module evaluation. To prevent an infinite recursion, pkgs and some of the modules are evaluated twice, which is inefficient. Using ‘with lib’ prevents this problem.
		
			
				
	
	
		
			62 lines
		
	
	
		
			1.2 KiB
		
	
	
	
		
			Nix
		
	
	
	
	
	
			
		
		
	
	
			62 lines
		
	
	
		
			1.2 KiB
		
	
	
	
		
			Nix
		
	
	
	
	
	
{ config, lib, pkgs, ... }:
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with lib;
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let
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  cfg = config.nix.gc;
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in
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{
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  ###### interface
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  options = {
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    nix.gc = {
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      automatic = mkOption {
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        default = false;
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        type = types.bool;
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        description = "Automatically run the garbage collector at a specific time.";
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      };
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      dates = mkOption {
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        default = "03:15";
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        type = types.str;
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        description = ''
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          Specification (in the format described by
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          <citerefentry><refentrytitle>systemd.time</refentrytitle>
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          <manvolnum>5</manvolnum></citerefentry>) of the time at
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          which the garbage collector will run.
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        '';
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      };
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      options = mkOption {
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        default = "";
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        example = "--max-freed $((64 * 1024**3))";
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        type = types.str;
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        description = ''
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          Options given to <filename>nix-collect-garbage</filename> when the
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          garbage collector is run automatically.
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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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    systemd.services.nix-gc =
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      { description = "Nix Garbage Collector";
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        script = "exec ${config.nix.package}/bin/nix-collect-garbage ${cfg.options}";
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        startAt = optionalString cfg.automatic cfg.dates;
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      };
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  };
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}
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