systemd-cron-next

What's it?

This is a compatibility layer for crontab-to-systemd timers framework. It works by parsing crontab and anacrontab files from usual places like /etc/crontab and /var/spool/cron and generating systemd timers and services. You can use cron.target as a single control point for the generated units.

It's intended to be a drop-in replacement for all cron implementations.

Rationale

The crontab generator for systemd (implemented in C) was already published on maillist, but was later declined by Lennart:

I am not convinced this is a really good idea. From my perspective at least it appears that we should much rather just convert the crontabs and that's it. Unlike sysv init scripts the number of crontab in use (at least on Fedora) is relatively small, and very rare in third-party packages.

Lennart

While I generally agree with him, I'm not totally convinced it's always convenient to herd a bunch of separate *.timer and *.service files. I find convenient to have all jobs schedule in one single file, and it's more obvious to see relations in jobs scheduling if you have several jobs in sight at once.

All things considered, I think people should have an alternative here, so I decided to support the idea of systemd crontab generator. Though the original C implementation of crontab parser from maillist is very incomplete: it doesn't support monotonic schedules (like @daily or @yearly), it can't parse comments and environment variable settings, etc.

Hence, I decided to create systemd-crontab-generator.

History

I'm not very good in C, so C implementation (while it's recommended for generators) whould take me ages to write, so at first, I used Python for proof-of-concept implementation. Then my small home project was noticed by @systemd-cron project and eventually was merged into it and evolved thanks to Alexandre Detiste, Dwayne Bent and others.

Still I bore in mind the image of the project's future: rewrite it in a systems language. Python, being VM-based scripting language is not the best choice for system service: it's slow (the slowest systemd generator ever, actually), have problems with multithreading, requires a lot of hacks like setgid/setuid C helper to implement crontab, etc.

Meanwhile the Rust systems language, I liked very much from the very beginning, reached its 1.0, so I decided to grab the moment and rewrite everything in Rust.

The current version you are looking at is meant to be a successor of @systemd-cron The project, entirely rewritten in Rust from ground up, while preserving experience, systemd unit templates and main algorithms and solutions polished in Python version by @systemd-cron team.

Usage

The generator runs on system boot and when the crontabs change.

The project includes simple crontab command equivalent, which behaves like standard crontab command (and accepts the same main options).

After installation add executable scripts to the appropriate cron directory (e.g. /etc/cron.daily) and enable systemd-cron:

# systemctl daemon-reload
# systemctl enable cron.target
# systemctl start cron.target

The scripts should now be automatically run by systemd. See man:systemd.cron(7) for more information.

To further control cron jobs, use cron.target unit.

Dependencies

systemd ≥ 197
- systemd ≥ 209, yearly timers
- systemd ≥ 212, persistent timers
- systemd ≥ 217, minutely, quarterly & semi-annually timers
- systemd ≥ 229, real random delay support with RandomizedDelaySec option
run-parts
/usr/sbin/sendmail (optional, evaluated at runtime)

Installation

If you are on Archlinux, install from AUR, otherwise see PKGBUILD file and execute commands from package() sub.

Packaging

Building

$ ./configure
$ make

You will need Rust stable compiler (tested with 1.5.0) and cargo tool to build the project.

Staging

$ make DESTDIR="$destdir" install

Configuration

The configure script takes command line arguments to configure various details of the build. The following options follow the standard GNU installation directories:

--prefix=<path>
--bindir=<path>
--confdir=<path>
--datadir=<path>
--libdir=<path>
--statedir=<path>
--mandir=<path>
--docdir=<path>

Other options include:

--unitdir=<path> Path to systemd unit files. Default: <libdir>/systemd/system.
--runparts=<path> The path installations should use for the run-parts executable. Default: <prefix>/bin/run-parts.
--enable-boot[=yes|no] Include support for the boot timer. Default: yes.
--enable-minutely[=yes|no] Include support for the minutely timer. Requires systemd ≥ 217. Default: no.
--enable-hourly[=yes|no] Include support for the hourly timer. Default: yes.
--enable-daily[=yes|no] Include support for the daily timer. Default: yes.
--enable-weekly[=yes|no] Include support for the weekly timer. Default: yes.
--enable-monthly[=yes|no] Include support for the monthly timer. Default: yes.
--enable-quarterly[=yes|no] Include support for the quarterly timer. Requires systemd ≥ 217. Default: no.
--enable-semi_annually[=yes|no] Include support for the semi-annually timer. Requires systemd ≥ 217. Default: no.
--enable-yearly[=yes|no] Include support for the yearly timer. Requires systemd ≥ 209. Default: no.
--enable-persistent[=yes|no] Make timers persistent. Requires systemd ≥ 212. Default: no.
--enable-randomized-delay=[yes|no] Use RandomizedDelaySec option for RANDOM_DELAY support. Requires systemd ≥ 229. Default: yes.
--enable-strip=[yes|no] Strip binaries. Default: yes.

A typical configuration for the latest systemd would be:

$ ./configure --prefix=/usr --confdir=/etc --enable-yearly --enable-persistent

If you only want the generator (you'll have to provide your own /etc/crontab to drive /etc/cron.daily/ etc...):

$ ./configure --enable-boot=no --enable-hourly=no --enable-daily=no --enable-weekly=no --enable-month=no --enable-persistent --prefix=/usr --confdir=/etc

Caveat

Your package should also run these extra commands before starting cron.target to ensure that @reboot scripts doesn't trigger right away:

# touch /run/crond.reboot
# touch /run/crond.bootdir

Disclaimer

This is a beta product! Use at your risk! I'm not responsible for any data losses, time losses, money losses or any other failures due to use or misuse of this project! I've run this product on my local server for several months without issues, but it does not mean you will have no issues as well! Don't blame me for any crashes because of the product! You were warned!

License

The main part of a project is licensed under MIT. Crontab man page is derived from Vixie Cron and licensed under Paul-Vixie's-license.

Contribution

You are most welcome to post bugs and PRs! Also, check out comments in AUR for current news about Arch package status.

Copyright

Original @systemd-cron project:

Systemd crontab generator evolution, tooling, and support:

Original systemd crontab generator code in Python, Rust version:

Systemd crontab generator man-page (man/systemd-crontab-generator.8.in):

Crontab man-page (man/crontab.5.in):

Numerous contributions via the Debian BTS copyright their respective authors

Debian packaging:

agrover/systemd-cron-next