4630ad4d26
Useful for setting up raid0-like load balancing for swap. By giving multiple swap devices the same prio.
125 lines
3.5 KiB
Nix
125 lines
3.5 KiB
Nix
{ config, pkgs, utils, ... }:
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with pkgs.lib;
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with utils;
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{
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###### interface
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options = {
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swapDevices = mkOption {
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default = [];
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example = [
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{ device = "/dev/hda7"; }
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{ device = "/var/swapfile"; }
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{ label = "bigswap"; }
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];
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description = ''
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The swap devices and swap files. These must have been
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initialised using <command>mkswap</command>. Each element
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should be an attribute set specifying either the path of the
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swap device or file (<literal>device</literal>) or the label
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of the swap device (<literal>label</literal>, see
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<command>mkswap -L</command>). Using a label is
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recommended.
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'';
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type = types.listOf types.optionSet;
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options = {config, options, ...}: {
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options = {
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device = mkOption {
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example = "/dev/sda3";
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type = types.uniq types.string;
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description = "Path of the device.";
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};
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label = mkOption {
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example = "swap";
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type = types.uniq types.string;
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description = ''
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Label of the device. Can be used instead of <varname>device</varname>.
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'';
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};
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size = mkOption {
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default = null;
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example = 2048;
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type = types.nullOr types.int;
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description = ''
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If this option is set, ‘device’ is interpreted as the
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path of a swapfile that will be created automatically
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with the indicated size (in megabytes) if it doesn't
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exist.
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'';
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};
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priority = mkOption {
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default = null;
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example = 2048;
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type = types.nullOr types.int;
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description = ''
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Specify the priority of the swap device. Priority is a value between 0 and 32767.
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Higher numbers indicate higher priority.
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null lets the kernel choose a priority, which will show up as a negative value.
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'';
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};
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};
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config = {
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device =
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if options.label.isDefined then
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"/dev/disk/by-label/${config.label}"
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else
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mkNotdef;
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};
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};
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};
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};
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config = mkIf ((length config.swapDevices) != 0) {
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system.requiredKernelConfig = with config.lib.kernelConfig; [
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(isYes "SWAP")
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];
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# Create missing swapfiles.
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# FIXME: support changing the size of existing swapfiles.
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systemd.services =
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let
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createSwapDevice = sw:
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assert sw.device != "";
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let device' = escapeSystemdPath sw.device; in
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nameValuePair "mkswap-${escapeSystemdPath sw.device}"
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{ description = "Initialisation of Swapfile ${sw.device}";
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wantedBy = [ "${device'}.swap" ];
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before = [ "${device'}.swap" ];
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path = [ pkgs.utillinux ];
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script =
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''
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if [ ! -e "${sw.device}" ]; then
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fallocate -l ${toString sw.size}M "${sw.device}" ||
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dd if=/dev/zero of="${sw.device}" bs=1M count=${toString sw.size}
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mkswap ${sw.device}
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fi
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'';
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unitConfig.RequiresMountsFor = [ "${dirOf sw.device}" ];
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unitConfig.DefaultDependencies = false; # needed to prevent a cycle
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serviceConfig.Type = "oneshot";
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};
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in listToAttrs (map createSwapDevice (filter (sw: sw.size != null) config.swapDevices));
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};
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}
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