nixpkgs/modules/services/scheduling/cron.nix

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{ config, pkgs, ... }:
with pkgs.lib;
let
inherit (config.services) jobsTags;
# Put all the system cronjobs together.
systemCronJobsFile = pkgs.writeText "system-crontab"
''
SHELL=${pkgs.bash}/bin/sh
PATH=${pkgs.coreutils}/bin:${pkgs.findutils}/bin:${pkgs.gnused}/bin:${pkgs.su}/bin
MAILTO="${config.services.cron.mailto}"
${pkgs.lib.concatStrings (map (job: job + "\n") config.services.cron.systemCronJobs)}
'';
in
{
###### interface
options = {
services.cron = {
mailto = mkOption {
default = "";
description = " The job output will be mailed to this email address. ";
};
systemCronJobs = mkOption {
default = [];
example = [
"* * * * * test ls -l / > /tmp/cronout 2>&1"
"* * * * * eelco echo Hello World > /home/eelco/cronout"
];
description = ''
A list of Cron jobs to be appended to the system-wide
crontab. See the manual page for crontab for the expected
format. If you want to get the results mailed you must setuid
sendmail. See <option>security.setuidOwners</option>
If neither /var/cron/cron.deny nor /var/cron/cron.allow exist only root
will is allowed to have its own crontab file. The /var/cron/cron.deny file
is created automatically for you. So every user can use a crontab.
'';
};
};
};
###### implementation
config = {
environment.etc = singleton
# The system-wide crontab.
{ source = systemCronJobsFile;
target = "crontab";
mode = "0600"; # Cron requires this.
};
environment.systemPackages = [pkgs.cron];
jobs.cron =
{ description = "Cron daemon";
startOn = "startup";
stopOn = "shutdown";
# Needed to interpret times in the local timezone.
environment = { TZ = config.time.timeZone; };
preStart =
''
mkdir -m 710 -p /var/cron
# By default, allow all users to create a crontab. This
# is denoted by the existence of an empty cron.deny file.
if ! test -e /var/cron/cron.allow -o -e /var/cron/cron.deny; then
touch /var/cron/cron.deny
fi
'';
exec = "${pkgs.cron}/sbin/cron -n";
};
};
}