path: root/nixos/modules/tasks/filesystems/zfs.nix

{ config, lib, options, pkgs, utils, ... }:
#
# TODO: zfs tunables

with utils;
with lib;

let

  cfgZfs = config.boot.zfs;
  optZfs = options.boot.zfs;
  cfgExpandOnBoot = config.services.zfs.expandOnBoot;
  cfgSnapshots = config.services.zfs.autoSnapshot;
  cfgSnapFlags = cfgSnapshots.flags;
  cfgScrub = config.services.zfs.autoScrub;
  cfgTrim = config.services.zfs.trim;
  cfgZED = config.services.zfs.zed;

  inInitrd = any (fs: fs == "zfs") config.boot.initrd.supportedFilesystems;
  inSystem = any (fs: fs == "zfs") config.boot.supportedFilesystems;

  autosnapPkg = pkgs.zfstools.override {
    zfs = cfgZfs.package;
  };

  zfsAutoSnap = "${autosnapPkg}/bin/zfs-auto-snapshot";

  datasetToPool = x: elemAt (splitString "/" x) 0;

  fsToPool = fs: datasetToPool fs.device;

  zfsFilesystems = filter (x: x.fsType == "zfs") config.system.build.fileSystems;

  allPools = unique ((map fsToPool zfsFilesystems) ++ cfgZfs.extraPools);

  rootPools = unique (map fsToPool (filter fsNeededForBoot zfsFilesystems));

  dataPools = unique (filter (pool: !(elem pool rootPools)) allPools);

  snapshotNames = [ "frequent" "hourly" "daily" "weekly" "monthly" ];

  # When importing ZFS pools, there's one difficulty: These scripts may run
  # before the backing devices (physical HDDs, etc.) of the pool have been
  # scanned and initialized.
  #
  # An attempted import with all devices missing will just fail, and can be
  # retried, but an import where e.g. two out of three disks in a three-way
  # mirror are missing, will succeed. This is a problem: When the missing disks
  # are later discovered, they won't be automatically set online, rendering the
  # pool redundancy-less (and far slower) until such time as the system reboots.
  #
  # The solution is the below. poolReady checks the status of an un-imported
  # pool, to see if *every* device is available -- in which case the pool will be
  # in state ONLINE, as opposed to DEGRADED, FAULTED or MISSING.
  #
  # The import scripts then loop over this, waiting until the pool is ready or a
  # sufficient amount of time has passed that we can assume it won't be. In the
  # latter case it makes one last attempt at importing, allowing the system to
  # (eventually) boot even with a degraded pool.
  importLib = {zpoolCmd, awkCmd, cfgZfs}: ''
    for o in $(cat /proc/cmdline); do
      case $o in
        zfs_force|zfs_force=1|zfs_force=y)
          ZFS_FORCE="-f"
          ;;
      esac
    done
    poolReady() {
      pool="$1"
      state="$("${zpoolCmd}" import 2>/dev/null | "${awkCmd}" "/pool: $pool/ { found = 1 }; /state:/ { if (found == 1) { print \$2; exit } }; END { if (found == 0) { print \"MISSING\" } }")"
      if [[ "$state" = "ONLINE" ]]; then
        return 0
      else
        echo "Pool $pool in state $state, waiting"
        return 1
      fi
    }
    poolImported() {
      pool="$1"
      "${zpoolCmd}" list "$pool" >/dev/null 2>/dev/null
    }
    poolImport() {
      pool="$1"
      "${zpoolCmd}" import -d "${cfgZfs.devNodes}" -N $ZFS_FORCE "$pool"
    }
  '';

  getPoolFilesystems = pool:
    filter (x: x.fsType == "zfs" && (fsToPool x) == pool) config.system.build.fileSystems;

  getPoolMounts = prefix: pool:
    let
      # Remove the "/" suffix because even though most mountpoints
      # won't have it, the "/" mountpoint will, and we can't have the
      # trailing slash in "/sysroot/" in stage 1.
      mountPoint = fs: escapeSystemdPath (prefix + (lib.removeSuffix "/" fs.mountPoint));
    in
      map (x: "${mountPoint x}.mount") (getPoolFilesystems pool);

  getKeyLocations = pool:
    if isBool cfgZfs.requestEncryptionCredentials
    then "${cfgZfs.package}/sbin/zfs list -rHo name,keylocation,keystatus ${pool}"
    else "${cfgZfs.package}/sbin/zfs list -Ho name,keylocation,keystatus ${toString (filter (x: datasetToPool x == pool) cfgZfs.requestEncryptionCredentials)}";

  createImportService = { pool, systemd, force, prefix ? "" }:
    nameValuePair "zfs-import-${pool}" {
      description = "Import ZFS pool \"${pool}\"";
      # we need systemd-udev-settle to ensure devices are available
      # In the future, hopefully someone will complete this:
      # https://github.com/zfsonlinux/zfs/pull/4943
      requires = [ "systemd-udev-settle.service" ];
      after = [
        "systemd-udev-settle.service"
        "systemd-modules-load.service"
        "systemd-ask-password-console.service"
      ];
      wantedBy = (getPoolMounts prefix pool) ++ [ "local-fs.target" ];
      before = (getPoolMounts prefix pool) ++ [ "local-fs.target" ];
      unitConfig = {
        DefaultDependencies = "no";
      };
      serviceConfig = {
        Type = "oneshot";
        RemainAfterExit = true;
      };
      environment.ZFS_FORCE = optionalString force "-f";
      script = (importLib {
        # See comments at importLib definition.
        zpoolCmd = "${cfgZfs.package}/sbin/zpool";
        awkCmd = "${pkgs.gawk}/bin/awk";
        inherit cfgZfs;
      }) + ''
        poolImported "${pool}" && exit
        echo -n "importing ZFS pool \"${pool}\"..."
        # Loop across the import until it succeeds, because the devices needed may not be discovered yet.
        for trial in `seq 1 60`; do
          poolReady "${pool}" && poolImport "${pool}" && break
          sleep 1
        done
        poolImported "${pool}" || poolImport "${pool}"  # Try one last time, e.g. to import a degraded pool.
        if poolImported "${pool}"; then
          ${optionalString (if isBool cfgZfs.requestEncryptionCredentials
                            then cfgZfs.requestEncryptionCredentials
                            else cfgZfs.requestEncryptionCredentials != []) ''
            ${getKeyLocations pool} | while IFS=$'\t' read ds kl ks; do
              {
              if [[ "$ks" != unavailable ]]; then
                continue
              fi
              case "$kl" in
                none )
                  ;;
                prompt )
                  tries=3
                  success=false
                  while [[ $success != true ]] && [[ $tries -gt 0 ]]; do
                    ${systemd}/bin/systemd-ask-password "Enter key for $ds:" | ${cfgZfs.package}/sbin/zfs load-key "$ds" \
                      && success=true \
                      || tries=$((tries - 1))
                  done
                  [[ $success = true ]]
                  ;;
                * )
                  ${cfgZfs.package}/sbin/zfs load-key "$ds"
                  ;;
              esac
              } < /dev/null # To protect while read ds kl in case anything reads stdin
            done
          ''}
          echo "Successfully imported ${pool}"
        else
          exit 1
        fi
      '';
    };

  zedConf = generators.toKeyValue {
    mkKeyValue = generators.mkKeyValueDefault {
      mkValueString = v:
        if isInt           v then toString v
        else if isString   v then "\"${v}\""
        else if true  ==   v then "1"
        else if false ==   v then "0"
        else if isList     v then "\"" + (concatStringsSep " " v) + "\""
        else err "this value is" (toString v);
    } "=";
  } cfgZED.settings;
in

{

  imports = [
    (mkRemovedOptionModule [ "boot" "zfs" "enableLegacyCrypto" ] "The corresponding package was removed from nixpkgs.")
  ];

  ###### interface

  options = {
    boot.zfs = {
      package = mkOption {
        readOnly = true;
        type = types.package;
        default = if config.boot.zfs.enableUnstable then pkgs.zfsUnstable else pkgs.zfs;
        defaultText = literalExpression "if config.boot.zfs.enableUnstable then pkgs.zfsUnstable else pkgs.zfs";
        description = lib.mdDoc "Configured ZFS userland tools package.";
      };

      enabled = mkOption {
        readOnly = true;
        type = types.bool;
        default = inInitrd || inSystem;
        defaultText = literalMD "`true` if ZFS filesystem support is enabled";
        description = lib.mdDoc "True if ZFS filesystem support is enabled";
      };

      enableUnstable = mkOption {
        type = types.bool;
        default = false;
        description = lib.mdDoc ''
          Use the unstable zfs package. This might be an option, if the latest
          kernel is not yet supported by a published release of ZFS. Enabling
          this option will install a development version of ZFS on Linux. The
          version will have already passed an extensive test suite, but it is
          more likely to hit an undiscovered bug compared to running a released
          version of ZFS on Linux.
          '';
      };

      extraPools = mkOption {
        type = types.listOf types.str;
        default = [];
        example = [ &quo