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this post was submitted on 13 Jul 2023
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People suggesting legacy methods like cron, but the only valid answer for modern Linux distributions is to use a systemd timer in userspace.
You just set up a service (what should be done and how do you want it to be done) and a timer (when should it be done).
https://gist.github.com/oprypin/0f0c3479ab53e00988b52919e5d7c144
Cron may be old but I don't think it's "legacy" or invalid. There's plenty of perfectly good, modern implementations. The interface is well established, and it's quite simple to schedule something and check it. What's more, Cron works on new Linux systems, older non-systemd ones, and BSD and others. If all you need is a command run on a schedule, then Cron is a great tool for the job.
Systemd services and timers require you to read quite a bit more documentation to understand what you're doing. But of course you get more power and flexibility as a result.
Yes. There is simply no reason not to make it state-of-the-art from the beginning on. You get proper logging, proper error handling, better scheduling options and you most likely don't even need to set up additional software because systemd (and thus systemd timers) are default in pretty much all common Linux distributions (except some niche ones) since 10+ years.
"simply no reason"?
What about ease of use, simplicity, faster to quickly setup, backwards compatibility, and "crobtab is where everyone will look at when looking for a scheduled task"?
If systemd was implemented right, it would create the systemd files and autoconfigure default tasks by reading the crontab, for backwards compatibility.
The syntax of systemd timers is MUCH easier to read for newbies (and everyone else, really) as it uses words instead the placement of the characters on the line to convey meaning. If you can't remember or don't know the syntax well you can still understand a systemd timer, but that is much hard for the crontab. Granted, crontab uses fewer characters, but if you only set up either once in a blue moon you'll need the docs to write either for a long time. And is backwards compatibility really an issue with either one? All major desktop and server distros use systemd, and has for a while. Fedora doesn't even include a Cron by default anymore.
If it was a distro release from the last decade I'd definitely start by checking the systemd timers, rather than the crontab.
You can to totally do this, using this systemd generator.
I will agree that it is easier to read a timer than a Cron entry, especially if you've seen neither of them before.
This is where I disagree. I very rarely setup a Cron job, but when I do, I don't need to look anywhere for docs. I run
crontab -eand the first line of the editor contains a comment which annotates each column of the Cron entry (minute, hour, dom, mon, dow). All that's left is to put in the matching expressions, and paste my command.Compare that to creating a new timer, where I need to Google a template
.serviceand.timerfile, and then figure out what to put in what fields from the docs. That's probably available in the manual pages, but I don't know which one. It's just not worth it unless I need the extra power from systemd.This is from somebody who has several systemd timers and also a few Cron jobs. I'm not a hater, just a person choosing the best and easiest choice for the job.