systemd timer, 定时任务

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# 查看 timer
systemctl list-timers
systemctl list-timers --all

创建一个服务

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vim /etc/systemd/system/foo.service

content of foo.service

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[Unit]
Description=foo service
[Service]
ExecStart=/usr/local/bin/foo.sh

[Install]
WantedBy=multi-user.target

再创建一个对应的 timer, /etc/systemd/system/foo.timer

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vim /etc/systemd/system/foo.timer

content of foo.timer

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[Unit]
Description=foo timer

[Timer]
# every 29 days
# OnUnitActiveSec=29d

# every day 12:00:00
OnCalendar=*-*-* 12:00:00

Persistent=true
Unit=foo.service

[Install]
WantedBy=multi-user.target

启用 timer

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systemctl enable --now foo.timer

http://www.ruanyifeng.com/blog/2018/03/systemd-timer.html

the basic format of Oncalnedar event

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* *-*-* *:*:*

It is divided into 3 parts -

  • * To signify the day of the week eg:- Sat,Thu,Mon
  • *-*-* To signify the calendar date. Which means it breaks down to - year-month-date.
    • 2021-10-15 is 15th of October
    • *-10-15 means every year at 15th October
    • *-01-01 means every new year.
  • *:*:* is to signify the time component of the calnedar event. So it is - hour:minute:second

[[cron#cron crond crontab linux 定时任务 cronie]]

https://silentlad.com/systemd-timers-oncalendar-(cron)-format-explained

  • Every day at 2am, *-*-* 02:00:00
  • every 29 days at 2am, *-*-* 02:00:00/29

systemd timer 相比 cron 的优点

  • 日志更丰富 journald
  • 可以设置内存和 CPU 的使用额度
  • 任务可以拆分，依赖其他 Systemd 单元，完成非常复杂的任务