Just learned of timers the other day, but I'm a cron guy, anybody out there using timers? Anything I'm missing out on?

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[–] 25 points 11 months ago (3 children)

Automatic failure handling, advanced logging, independent execution environment control, cgroups support, service dependency management...

On the negative side, it takes slightly more work to configure timed tasks and there's no integrated email support.

Refer to the Arch Wiki for more detailed information.

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  • [–] 4 points 11 months ago

    Email support was the bain of my existence. I forgot how many misconfigured system I came across decades ago that would fill up their filesystem with logs from crons in the root mail dir. Such a stupid default setting. We have vastly better methods for monitoring systems these days then firing off an email when a cron runs.

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  • [–] 16 points 11 months ago (3 children)

    Also a cron guy, but systemd timers can do things like run at a preset time after start up if a schedule was missed due to power off or system suspension, and you can get more information about a failed timer with journalctl. Arch wiki has lots of good info. Still, I'm a cron guy. 🤷‍♂️ Set in my ways

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  • [–] 3 points 11 months ago* (2 children)

    You can do the same with cron btw depending on the OS(?). At least on debian systems. I think its @poweroff or @reboot if I recall correctly.

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  • [–] 2 points 11 months ago (1 child)

    It’s more than just power state, you can also toggle based on the state of other units (which you could chain normally too, but not time based) so you could start a service 10 minutes after another service has ran to completion, or after it’s died, etc.

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  • [–] 14 points 11 months ago* (1 child)

    My number one reason for using systemd timers is just that I find it more readable than cron. Usually I want to run things daily, weekly or monthlyand systemd timers make that very easy.

    Here is an example:

    backup.timer

    [Unit]
    Description=Run backup database daily
    
    [Timer]
    OnCalendar=daily
    RandomizedDelaySec=10
    
    [Install]
    WantedBy=timers.target
    

    backup.service

    [Unit]
    Description=Backup database
    
    [Service]
    Type=oneshot
    ExecStart=/bin/bash /path/to/backupscript.sh
    

    Another great feature is that the output of the script is logged to journald which is very convenient when you are troubleshooting why your backup failed last night.

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  • [–] 5 points 11 months ago

    I was literally just pondering this. I've got a local backup job that is a very simple rsync command which I originally setup as a cron job. I've got a cloud backup job I setup later with systemd timers. I went to add a new backup job and had to decide which to go with.

    There is absolutely still a place for the cron jobs. If you are aware of it's limitations it cannot get simpler than a new /etc/cron.d/ file with a single line. But the systemd timer path offers some nice functionality in exchange for a tad more complexity and less footguns. Whichever one you understand the best is probably the best answer.

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  • [–] 8 points 11 months ago

    If you already know cron and are too lazy to learn something new, then use cron with the knowledge that it's a personal failure and not a real technical decision... Otherwise, use systemd timers.

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  • [–] 3 points 11 months ago

    For me ive always used:

    • cron if its simple and can take care of itself.
    • systemd if its more complex and needs the OS to do a thing related.

    Its not a hard set rule but its like 95% cron and some systemd on the side for me.

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  • [–] 2 points 11 months ago

    My system has timers, but I use cron anyway. It's more simple, IMO.

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  • [–] 1 point 11 months ago

    The entirety of cron documentation is contained in the twenty lines of comments in the new config file created by cron -e

    The only thing you need to know is cron -e command. There's no learning curve, it's more like - you are a cron expert in five minutes after learning that such a tool exists.

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