1 files changed, 138 insertions, 0 deletions
diff --git a/nixos/modules/services/scheduling/cron.nix b/nixos/modules/services/scheduling/cron.nix
new file mode 100644
index 00000000000..1fac54003cb
--- /dev/null
+++ b/nixos/modules/services/scheduling/cron.nix
@@ -0,0 +1,138 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  # Put all the system cronjobs together.
+  systemCronJobsFile = pkgs.writeText "system-crontab"
+    ''
+      SHELL=${pkgs.bash}/bin/bash
+      PATH=${config.system.path}/bin:${config.system.path}/sbin
+      ${optionalString (config.services.cron.mailto != null) ''
+        MAILTO="${config.services.cron.mailto}"
+      ''}
+      NIX_CONF_DIR=/etc/nix
+      ${lib.concatStrings (map (job: job + "\n") config.services.cron.systemCronJobs)}
+    '';
+
+  # Vixie cron requires build-time configuration for the sendmail path.
+  cronNixosPkg = pkgs.cron.override {
+    # The mail.nix nixos module, if there is any local mail system enabled,
+    # should have sendmail in this path.
+    sendmailPath = "/run/wrappers/bin/sendmail";
+  };
+
+  allFiles =
+    optional (config.services.cron.systemCronJobs != []) systemCronJobsFile
+    ++ config.services.cron.cronFiles;
+
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    services.cron = {
+
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        description = "Whether to enable the Vixie cron daemon.";
+      };
+
+      mailto = mkOption {
+        type = types.nullOr types.str;
+        default = null;
+        description = "Email address to which job output will be mailed.";
+      };
+
+      systemCronJobs = mkOption {
+        type = types.listOf types.str;
+        default = [];
+        example = literalExpression ''
+          [ "* * * * *  test   ls -l / > /tmp/cronout 2>&1"
+            "* * * * *  eelco  echo Hello World > /home/eelco/cronout"
+          ]
+        '';
+        description = ''
+          A list of Cron jobs to be appended to the system-wide
+          crontab.  See the manual page for crontab for the expected
+          format. If you want to get the results mailed you must setuid
+          sendmail. See <option>security.wrappers</option>
+
+          If neither /var/cron/cron.deny nor /var/cron/cron.allow exist only root
+          is allowed to have its own crontab file. The /var/cron/cron.deny file
+          is created automatically for you, so every user can use a crontab.
+
+          Many nixos modules set systemCronJobs, so if you decide to disable vixie cron
+          and enable another cron daemon, you may want it to get its system crontab
+          based on systemCronJobs.
+        '';
+      };
+
+      cronFiles = mkOption {
+        type = types.listOf types.path;
+        default = [];
+        description = ''
+          A list of extra crontab files that will be read and appended to the main
+          crontab file when the cron service starts.
+        '';
+      };
+
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = mkMerge [
+
+    { services.cron.enable = mkDefault (allFiles != []); }
+    (mkIf (config.services.cron.enable) {
+      security.wrappers.crontab =
+        { setuid = true;
+          owner = "root";
+          group = "root";
+          source = "${cronNixosPkg}/bin/crontab";
+        };
+      environment.systemPackages = [ cronNixosPkg ];
+      environment.etc.crontab =
+        { source = pkgs.runCommand "crontabs" { inherit allFiles; preferLocalBuild = true; }
+            ''
+              touch $out
+              for i in $allFiles; do
+                cat "$i" >> $out
+              done
+            '';
+          mode = "0600"; # Cron requires this.
+        };
+
+      systemd.services.cron =
+        { description = "Cron Daemon";
+
+          wantedBy = [ "multi-user.target" ];
+
+          preStart =
+            ''
+              mkdir -m 710 -p /var/cron
+
+              # By default, allow all users to create a crontab.  This
+              # is denoted by the existence of an empty cron.deny file.
+              if ! test -e /var/cron/cron.allow -o -e /var/cron/cron.deny; then
+                  touch /var/cron/cron.deny
+              fi
+            '';
+
+          restartTriggers = [ config.time.timeZone ];
+          serviceConfig.ExecStart = "${cronNixosPkg}/bin/cron -n";
+        };
+
+    })
+
+  ];
+
+}