{ config, pkgs, ... }: with pkgs.lib; { ###### interface options = { swapDevices = mkOption { default = []; example = [ { device = "/dev/hda7"; } { device = "/var/swapfile"; } { label = "bigswap"; } ]; description = '' The swap devices and swap files. These must have been initialised using mkswap. Each element should be an attribute set specifying either the path of the swap device or file (device) or the label of the swap device (label, see mkswap -L). Using a label is recommended. ''; type = types.list types.optionSet; options = {config, options, ...}: { options = { device = mkOption { example = "/dev/sda3"; type = types.uniq types.string; description = "Path of the device."; }; label = mkOption { example = "swap"; type = types.uniq types.string; description = '' Label of the device. Can be used instead of device. ''; }; size = mkOption { default = null; example = 2048; type = types.nullOr types.int; description = '' If this option is set, ‘device’ is interpreted as the path of a swapfile that will be created automatically with the indicated size (in megabytes) if it doesn't exist. ''; }; }; config = { device = if options.label.isDefined then "/dev/disk/by-label/${config.label}" else mkNotdef; }; }; }; }; config = mkIf ((length config.swapDevices) != 0) { system.requiredKernelConfig = with config.lib.kernelConfig; [ (isYes "SWAP") ]; # Create missing swapfiles. # FIXME: support changing the size of existing swapfiles. boot.systemd.services = let escapePath = s: # FIXME: slow replaceChars ["/" "-"] ["-" "\\x2d"] (substring 1 (stringLength s) s); createSwapDevice = sw: assert sw.device != ""; nameValuePair "mkswap-${escapePath sw.device}" { description = "Initialisation of Swapfile ${sw.device}"; wantedBy = [ "${escapePath sw.device}.swap" ]; before = [ "${escapePath sw.device}.swap" ]; path = [ pkgs.utillinux ]; script = '' if [ ! -e "${sw.device}" ]; then fallocate -l ${toString sw.size}M "${sw.device}" || dd if=/dev/zero of="${sw.device}" bs=1M count=${toString sw.size} mkswap ${sw.device} fi ''; unitConfig.RequiresMountsFor = "${dirOf sw.device}"; unitConfig.DefaultDependencies = false; # needed to prevent a cycle serviceConfig.Type = "oneshot"; serviceConfig.RemainAfterExit = true; }; in listToAttrs (map createSwapDevice (filter (sw: sw.size != null) config.swapDevices)); }; }