306 lines
10 KiB
Nix
306 lines
10 KiB
Nix
{ config, lib, pkgs, utils, ... }:
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let
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inherit (lib) mkIf mkOption types;
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randomEncryptionCoerce = enable: { inherit enable; };
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randomEncryptionOpts = { ... }: {
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options = {
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enable = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Encrypt swap device with a random key. This way you won't have a persistent swap device.
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WARNING: Don't try to hibernate when you have at least one swap partition with
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this option enabled! We have no way to set the partition into which hibernation image
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is saved, so if your image ends up on an encrypted one you would lose it!
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WARNING #2: Do not use /dev/disk/by-uuid/… or /dev/disk/by-label/… as your swap device
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when using randomEncryption as the UUIDs and labels will get erased on every boot when
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the partition is encrypted. Best to use /dev/disk/by-partuuid/…
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'';
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};
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cipher = mkOption {
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default = "aes-xts-plain64";
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example = "serpent-xts-plain64";
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type = types.str;
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description = ''
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Use specified cipher for randomEncryption.
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Hint: Run "cryptsetup benchmark" to see which one is fastest on your machine.
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'';
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};
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keySize = mkOption {
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default = null;
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example = "512";
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type = types.nullOr types.int;
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description = ''
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Set the encryption key size for the plain device.
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If not specified, the amount of data to read from `source` will be
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determined by cryptsetup.
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See `cryptsetup-open(8)` for details.
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'';
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};
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sectorSize = mkOption {
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default = null;
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example = "4096";
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type = types.nullOr types.int;
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description = ''
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Set the sector size for the plain encrypted device type.
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If not specified, the default sector size is determined from the
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underlying block device.
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See `cryptsetup-open(8)` for details.
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'';
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};
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source = mkOption {
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default = "/dev/urandom";
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example = "/dev/random";
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type = types.str;
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description = ''
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Define the source of randomness to obtain a random key for encryption.
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'';
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};
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allowDiscards = mkOption {
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default = false;
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type = types.bool;
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description = ''
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Whether to allow TRIM requests to the underlying device. This option
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has security implications; please read the LUKS documentation before
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activating it.
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'';
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};
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};
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};
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swapCfg = {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.nonEmptyStr;
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description = "Path of the device or swap file.";
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};
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label = mkOption {
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example = "swap";
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type = types.str;
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description = ''
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Label of the device. Can be used instead of {var}`device`.
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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).
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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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randomEncryption = mkOption {
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default = false;
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example = {
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enable = true;
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cipher = "serpent-xts-plain64";
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source = "/dev/random";
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};
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type = types.coercedTo types.bool randomEncryptionCoerce (types.submodule randomEncryptionOpts);
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description = ''
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Encrypt swap device with a random key. This way you won't have a persistent swap device.
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HINT: run "cryptsetup benchmark" to test cipher performance on your machine.
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WARNING: Don't try to hibernate when you have at least one swap partition with
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this option enabled! We have no way to set the partition into which hibernation image
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is saved, so if your image ends up on an encrypted one you would lose it!
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WARNING #2: Do not use /dev/disk/by-uuid/… or /dev/disk/by-label/… as your swap device
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when using randomEncryption as the UUIDs and labels will get erased on every boot when
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the partition is encrypted. Best to use /dev/disk/by-partuuid/…
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'';
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};
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discardPolicy = mkOption {
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default = null;
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example = "once";
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type = types.nullOr (types.enum ["once" "pages" "both" ]);
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description = ''
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Specify the discard policy for the swap device. If "once", then the
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whole swap space is discarded at swapon invocation. If "pages",
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asynchronous discard on freed pages is performed, before returning to
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the available pages pool. With "both", both policies are activated.
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See swapon(8) for more information.
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'';
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};
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options = mkOption {
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default = [ "defaults" ];
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example = [ "nofail" ];
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type = types.listOf types.nonEmptyStr;
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description = ''
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Options used to mount the swap.
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'';
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};
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deviceName = mkOption {
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type = types.str;
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internal = true;
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};
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realDevice = mkOption {
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type = types.path;
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internal = true;
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};
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};
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config = {
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device = mkIf options.label.isDefined
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"/dev/disk/by-label/${config.label}";
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deviceName = lib.replaceStrings ["\\"] [""] (utils.escapeSystemdPath config.device);
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realDevice = if config.randomEncryption.enable then "/dev/mapper/${config.deviceName}" else config.device;
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};
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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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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`. 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 (`device`) or the label
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of the swap device (`label`, see
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{command}`mkswap -L`). Using a label is
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recommended.
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'';
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type = types.listOf (types.submodule swapCfg);
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};
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};
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config = mkIf ((lib.length config.swapDevices) != 0) {
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assertions = lib.map (sw: {
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assertion = sw.randomEncryption.enable -> builtins.match "/dev/disk/by-(uuid|label)/.*" sw.device == null;
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message = ''
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You cannot use swap device "${sw.device}" with randomEncryption enabled.
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The UUIDs and labels will get erased on every boot when the partition is encrypted.
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Use /dev/disk/by-partuuid/… instead.
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'';
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}) config.swapDevices;
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warnings =
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lib.concatMap (sw:
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if sw.size != null && lib.hasPrefix "/dev/" sw.device
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then [ "Setting the swap size of block device ${sw.device} has no effect" ]
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else [ ])
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config.swapDevices;
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system.requiredKernelConfig = [
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(config.lib.kernelConfig.isYes "SWAP")
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];
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# Create missing swapfiles.
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systemd.services =
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let
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createSwapDevice = sw:
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let realDevice' = utils.escapeSystemdPath sw.realDevice;
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in lib.nameValuePair "mkswap-${sw.deviceName}"
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{ description = "Initialisation of swap device ${sw.device}";
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# The mkswap service fails for file-backed swap devices if the
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# loop module has not been loaded before the service runs.
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# We add an ordering constraint to run after systemd-modules-load to
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# avoid this race condition.
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after = [ "systemd-modules-load.service" ];
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wantedBy = [ "${realDevice'}.swap" ];
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before = [ "${realDevice'}.swap" "shutdown.target"];
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conflicts = [ "shutdown.target" ];
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path = [ pkgs.util-linux pkgs.e2fsprogs ]
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++ lib.optional sw.randomEncryption.enable pkgs.cryptsetup;
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environment.DEVICE = sw.device;
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script =
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''
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${lib.optionalString (sw.size != null) ''
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currentSize=$(( $(stat -c "%s" "$DEVICE" 2>/dev/null || echo 0) / 1024 / 1024 ))
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if [[ ! -b "$DEVICE" && "${toString sw.size}" != "$currentSize" ]]; then
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# Disable CoW for CoW based filesystems like BTRFS.
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truncate --size 0 "$DEVICE"
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chattr +C "$DEVICE" 2>/dev/null || true
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echo "Creating swap file using dd and mkswap."
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dd if=/dev/zero of="$DEVICE" bs=1M count=${toString sw.size} status=progress
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${lib.optionalString (!sw.randomEncryption.enable) "mkswap ${sw.realDevice}"}
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fi
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''}
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${lib.optionalString sw.randomEncryption.enable ''
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cryptsetup plainOpen -c ${sw.randomEncryption.cipher} -d ${sw.randomEncryption.source} \
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${lib.concatStringsSep " \\\n" (lib.flatten [
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(lib.optional (sw.randomEncryption.sectorSize != null) "--sector-size=${toString sw.randomEncryption.sectorSize}")
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(lib.optional (sw.randomEncryption.keySize != null) "--key-size=${toString sw.randomEncryption.keySize}")
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(lib.optional sw.randomEncryption.allowDiscards "--allow-discards")
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])} ${sw.device} ${sw.deviceName}
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mkswap ${sw.realDevice}
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''}
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'';
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unitConfig.RequiresMountsFor = [ "${dirOf sw.device}" ];
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unitConfig.DefaultDependencies = false; # needed to prevent a cycle
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serviceConfig = {
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Type = "oneshot";
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RemainAfterExit = sw.randomEncryption.enable;
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UMask = "0177";
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ExecStop = lib.optionalString sw.randomEncryption.enable "${pkgs.cryptsetup}/bin/cryptsetup luksClose ${sw.deviceName}";
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};
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restartIfChanged = false;
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};
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in lib.listToAttrs (lib.map createSwapDevice (lib.filter (sw: sw.size != null || sw.randomEncryption.enable) config.swapDevices));
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};
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}
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