add zquota to easily monitor disk usage of zfs datasets

1 files changed, 77 insertions, 0 deletions

diff --git a/modules/scripts/zquota/default.nix b/modules/scripts/zquota/default.nix
new file mode 100644
index 0000000..1dc1fbd
--- /dev/null
+++ b/modules/scripts/zquota/default.nix
@@ -0,0 +1,77 @@
+{ config, lib, pkgs, ... }:
+with lib;
+let
+  cfg = config.services.zquota;
+
+  zquota = let hostname = config.networking.hostName; in
+    pkgs.writeShellScriptBin "zquota" ''
+      #!/usr/bin/env bash
+
+      if [ "$#" -ne 2 ]; then
+        echo "failed to provide both a dataset and quota" >&2
+        exit 1
+      fi
+
+      DATASET="$1"
+      QUOTA="$2"
+
+      if [ -n "$(echo "$QUOTA" | tr -d 0-9.)" ]; then
+        echo "failed to provide a valid quota" >&2
+        exit 1
+      fi
+
+      USED=$(${getExe pkgs.zfs} list -Hpo used "$DATASET" 2>/dev/null) || {
+        echo "failed to provide a valid dataset" >&2
+        exit 1
+      }
+
+      USAGE=$(${getExe pkgs.bc} <<< "scale=2; $NUM / 1024^3")
+
+      DIFF=$(${getExe pkgs.bc} <<< "scale=2; $NUM - $QUOTA")
+
+      (( $(awk '{ print ($1 > $2) }' <<< "$USAGE $QUOTA") )) &&
+        /run/current-system/sw/bin/pushover -t "${hostname} quota exceeded" \
+        "dataset $DATASET on ${hostname} has exceeded quota by ''${DIFF}GB"
+    '';
+in
+{
+  options = {
+    services.zquota = {
+      enable = mkEnableOption "zquota";
+      quotas = mkOption {
+        default = { };
+        type = types.attrsOf types.int;
+        description = "Attribute set of ZFS dataset and disk quota (in GB).";
+      };
+      dates = mkOption {
+        default = "daily";
+        type = types.str;
+        description = ''
+          How often quota checks are performed.
+
+          This value must be a calendar event specified by
+          {manpage}`systemd.time(7)`.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ zquota ];
+
+    systemd.services."zquota" = {
+      description = "Perform and report routine quota checks on ZFS datasets";
+      serviceConfig.Type = "oneshot";
+      script = strings.concatStringsSep "\n" <| mapAttrsToList (
+        dataset: quota: "/run/current-system/sw/bin/zquota ${dataset} ${builtins.toString quota}"
+      ) cfg.quotas;
+    };
+    systemd.timers."zquota" = {
+      wantedBy = [ "timers.target" ];
+      timerConfig = {
+        OnCalendar = cfg.dates;
+        Persistent = true;
+      };
+    };
+  };
+}