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nixpkgs/nixos/modules/services/scheduling/cron.nix
2021-10-04 12:47:20 +02:00

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3.9 KiB
Nix

{ 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";
};
})
];
}