Added basic rsnapshot backup.

mail-server/rsnapshot.nix

@@ -0,0 +1,59 @@
+#  nixos-mailserver: a simple mail server
+#  Copyright (C) 2016-2017  Robin Raymond
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program. If not, see <http://www.gnu.org/licenses/>
+
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.mailserver;
+
+  preexecDefined = cfg.backup.cmdPreexec != null;
+  preexecWrapped = pkgs.writeScript "rsnapshot-preexec.sh" ''
+    #!${pkgs.stdenv.shell}
+    set -e
+
+    ${cfg.backup.cmdPreexec}
+  '';
+  preexecString = optionalString preexecDefined "cmd_preexec	${preexecWrapped}";
+
+  postexecDefined = cfg.backup.cmdPostexec != null;
+  postexecWrapped = pkgs.writeScript "rsnapshot-postexec.sh" ''
+    #!${pkgs.stdenv.shell}
+    set -e
+
+    ${cfg.backup.cmdPostexec}
+  '';
+  postexecString = optionalString postexecDefined "cmd_postexec	${postexecWrapped}";
+in {
+  config = mkIf cfg.backup.enable {
+    services.rsnapshot = {
+      enable = true;
+      cronIntervals = cfg.backup.cronIntervals;
+      # rsnapshot expects intervals shortest first, e.g. hourly first, then daily.
+      # tabs must separate all elements
+      extraConfig = ''
+        ${preexecString}
+        ${postexecString}
+        snapshot_root	${cfg.backup.snapshotRoot}/
+        retain	hourly	${toString cfg.backup.retain.hourly}
+        retain	daily	${toString cfg.backup.retain.daily}
+        retain	weekly	${toString cfg.backup.retain.weekly}
+        backup	${cfg.mailDirectory}/	localhost/
+      '';
+    };
+  };
+}