Power Management: Difference between revisions

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~~{{expansion}}~~

This article covers configurations related to power management in terms of energy saving modes of various devices and components.

== ~~Suspend~~ ==

== Configuration ==

=== Hard drive power management ===

Following snippet configures [[Udev]] rules which automatically run the program <code>hdparm</code> to enable power saving modes for hard disks, especially rotational drives mapped to <code>/dev/sd*</code>.<syntaxhighlight lang="nix">

services.udev.extraRules =

let

mkRule = as: lib.concatStringsSep ", " as;

mkRules = rs: lib.concatStringsSep "\n" rs;

in mkRules ([( mkRule [

''ACTION=="add|change"''

''SUBSYSTEM=="block"''

''KERNEL=="sd[a-z]"''

''ATTR{queue/rotational}=="1"''

''RUN+="${pkgs.hdparm}/bin/hdparm -B 90 -S 41 /dev/%k"''

])]);

</syntaxhighlight>The <code>hdparm</code> parameters <code>-B</code> and <code>-S</code> define power saving modes and in case of <code>-S</code> the standby (spindown) timeout. The number 41 means therefore: Turn off the motor after 205 = 41*5 seconds.

=== Suspend hooks ===

NixOS provides the {{nixos:option|powerManagement.resumeCommands}} option which defines commands that are added to a global script that will be executed after resuming.

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</syntaxhighlight>

== Hibernation ==

=== Hibernation ===

Hibernation requires a configured swap device. See [https://nixos.org/manual/nixos/stable/#ch-installation installation instructions] on how to create a swap partition. An example configuration could look like this:<syntaxhighlight lang="nix">

swapDevices = [

@@ Line 1: / Line 1: @@
-{{expansion}}
+This article covers configurations related to power management in terms of energy saving modes of various devices and components.
-== Suspend ==
+== Configuration ==
+=== Hard drive power management ===
+Following snippet configures [[Udev]] rules which automatically run the program <code>hdparm</code> to enable power saving modes for hard disks, especially rotational drives mapped to <code>/dev/sd*</code>.<syntaxhighlight lang="nix">
+services.udev.extraRules =
+  let
+    mkRule = as: lib.concatStringsSep ", " as;
+    mkRules = rs: lib.concatStringsSep "\n" rs;
+  in mkRules ([( mkRule [
+    ''ACTION=="add|change"''
+    ''SUBSYSTEM=="block"''
+    ''KERNEL=="sd[a-z]"''
+    ''ATTR{queue/rotational}=="1"''
+    ''RUN+="${pkgs.hdparm}/bin/hdparm -B 90 -S 41 /dev/%k"''
+  ])]);
+</syntaxhighlight>The <code>hdparm</code> parameters <code>-B</code> and <code>-S</code> define power saving modes and in case of <code>-S</code> the standby (spindown) timeout. The number 41 means therefore: Turn off the motor after 205 = 41*5 seconds.
 === Suspend hooks ===
 NixOS provides the {{nixos:option|powerManagement.resumeCommands}} option which defines commands that are added to a global script that will be executed after resuming.
@@ Line 27: / Line 41: @@
 </syntaxhighlight>
-== Hibernation ==
+=== Hibernation ===
 Hibernation requires a configured swap device. See [https://nixos.org/manual/nixos/stable/#ch-installation installation instructions] on how to create a swap partition. An example configuration could look like this:<syntaxhighlight lang="nix">
 swapDevices = [