Product SiteDocumentation Site

9.8. 排定非同步工作:anacron

anacron 適用於無法全天候開機的電腦,用以取代 cron 後台進程。通常半夜執行由於常規的工作,若已關機就無法執行它。anacron 的目的就是考量這種情況,讓該做的工作仍然能執行。
Please note that anacron will frequently execute such activity a few minutes after booting the machine, which can render the computer less responsive. This is why the tasks in the /etc/anacrontab file are started with the nice command, which reduces their execution priority and thus limits their impact on the rest of the system. Beware, the format of this file is not the same as that of /etc/crontab; if you have particular needs for anacron, see the anacrontab(5) manual page.
Installation of the anacron package deactivates execution by cron of the scripts in the /etc/cron.hourly/, /etc/cron.daily/, /etc/cron.weekly/, and /etc/cron.monthly/ directories. This avoids their double execution by anacron and cron. The cron command remains active and will continue to handle the other scheduled tasks (especially those scheduled by users).