pyrox.dev
lol
nixos/btrfs: add services.btrfs.autoScrub for automatic regular scrubbing of mounted btrfs filesystems, similar to what's already there for zfs.
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nixos/doc/manual/release-notes/rl-1803.xml
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nixos/doc/manual/release-notes/rl-1803.xml
···
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Previously the default behaviour was to listen on all interfaces.
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</para>
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</listitem>
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<listitem>
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<para>
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<literal>services.btrfs.autoScrub</literal> has been added, to
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periodically check btrfs filesystems for data corruption.
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If there's a correct copy available, it will automatically repair
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corrupted blocks.
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</para>
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</listitem>
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</itemizedlist>
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</section>
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nixos/modules/tasks/filesystems/btrfs.nix
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nixos/modules/tasks/filesystems/btrfs.nix
···
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{ config, lib, pkgs, ... }:
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with lib;
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let
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inInitrd = any (fs: fs == "btrfs") config.boot.initrd.supportedFilesystems;
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in
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{
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config = mkIf (any (fs: fs == "btrfs") config.boot.supportedFilesystems) {
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system.fsPackages = [ pkgs.btrfs-progs ];
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boot.initrd.kernelModules = mkIf inInitrd [ "btrfs" "crc32c" ];
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boot.initrd.extraUtilsCommands = mkIf inInitrd
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''
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copy_bin_and_libs ${pkgs.btrfs-progs}/bin/btrfs
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ln -sv btrfs $out/bin/btrfsck
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ln -sv btrfsck $out/bin/fsck.btrfs
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'';
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boot.initrd.extraUtilsCommandsTest = mkIf inInitrd
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''
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$out/bin/btrfs --version
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'';
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boot.initrd.postDeviceCommands = mkIf inInitrd
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''
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btrfs device scan
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'';
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};
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}
···
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{ config, lib, pkgs, utils, ... }:
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with lib;
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let
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inInitrd = any (fs: fs == "btrfs") config.boot.initrd.supportedFilesystems;
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inSystem = any (fs: fs == "btrfs") config.boot.supportedFilesystems;
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cfgScrub = config.services.btrfs.autoScrub;
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enableAutoScrub = cfgScrub.enable;
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enableBtrfs = inInitrd || inSystem || enableAutoScrub;
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in
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{
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options = {
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# One could also do regular btrfs balances, but that shouldn't be necessary
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# during normal usage and as long as the filesystems aren't filled near capacity
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services.btrfs.autoScrub = {
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enable = mkEnableOption "Enable regular btrfs scrub";
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fileSystems = mkOption {
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type = types.listOf types.path;
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example = [ "/" ];
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description = ''
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List of paths to btrfs filesystems to regularily call <command>btrfs scrub</command> on.
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Defaults to all mount points with btrfs filesystems.
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If you mount a filesystem multiple times or additionally mount subvolumes,
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you need to manually specify this list to avoid scrubbing multiple times.
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'';
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};
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interval = mkOption {
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default = "monthly";
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type = types.str;
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example = "weekly";
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description = ''
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Systemd calendar expression for when to scrub btrfs filesystems.
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The recommended period is a month but could be less
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(<citerefentry><refentrytitle>btrfs-scrub</refentrytitle>
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<manvolnum>8</manvolnum></citerefentry>).
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See
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<citerefentry><refentrytitle>systemd.time</refentrytitle>
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<manvolnum>7</manvolnum></citerefentry>
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for more information on the syntax.
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'';
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};
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};
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};
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config = mkMerge [
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(mkIf enableBtrfs {
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system.fsPackages = [ pkgs.btrfs-progs ];
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boot.initrd.kernelModules = mkIf inInitrd [ "btrfs" "crc32c" ];
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boot.initrd.extraUtilsCommands = mkIf inInitrd
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''
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copy_bin_and_libs ${pkgs.btrfs-progs}/bin/btrfs
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ln -sv btrfs $out/bin/btrfsck
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ln -sv btrfsck $out/bin/fsck.btrfs
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'';
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boot.initrd.extraUtilsCommandsTest = mkIf inInitrd
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''
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$out/bin/btrfs --version
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'';
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boot.initrd.postDeviceCommands = mkIf inInitrd
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''
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btrfs device scan
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'';
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})
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(mkIf enableAutoScrub {
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assertions = [
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{
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assertion = cfgScrub.enable -> (cfgScrub.fileSystems != []);
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message = ''
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If 'services.btrfs.autoScrub' is enabled, you need to have at least one
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btrfs file system mounted via 'fileSystems' or specify a list manually
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in 'services.btrfs.autoScrub.fileSystems'.
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'';
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}
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];
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# This will yield duplicated units if the user mounts a filesystem multiple times
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# or additionally mounts subvolumes, but going the other way around via devices would
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# yield duplicated units when a filesystem spans multiple devices.
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# This way around seems like the more sensible default.
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services.btrfs.autoScrub.fileSystems = mkDefault (mapAttrsToList (name: fs: fs.mountPoint)
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(filterAttrs (name: fs: fs.fsType == "btrfs") config.fileSystems));
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# TODO: Did not manage to do it via the usual btrfs-scrub@.timer/.service
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# template units due to problems enabling the parameterized units,
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# so settled with many units and templating via nix for now.
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# https://github.com/NixOS/nixpkgs/pull/32496#discussion_r156527544
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systemd.timers = let
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scrubTimer = fs: let
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fs' = utils.escapeSystemdPath fs;
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in nameValuePair "btrfs-scrub-${fs'}" {
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description = "regular btrfs scrub timer on ${fs}";
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wantedBy = [ "timers.target" ];
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timerConfig = {
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OnCalendar = cfgScrub.interval;
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AccuracySec = "1d";
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Persistent = true;
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};
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};
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in listToAttrs (map scrubTimer cfgScrub.fileSystems);
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systemd.services = let
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scrubService = fs: let
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fs' = utils.escapeSystemdPath fs;
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in nameValuePair "btrfs-scrub-${fs'}" {
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description = "btrfs scrub on ${fs}";
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serviceConfig = {
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Type = "oneshot";
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Nice = 19;
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IOSchedulingClass = "idle";
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ExecStart = "${pkgs.btrfs-progs}/bin/btrfs scrub start -B ${fs}";
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};
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};
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in listToAttrs (map scrubService cfgScrub.fileSystems);
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})
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];
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}