CentOS7使用cron和anacron用来定期重复执行指令
    rpm -q yum-cron

    yum -y install cronie

    yum -y install yum-cron

单独安装yum-cron也可以,因为yum会自动检测到yum-cron需要一来到cronie然后自动安装
    systemctl start crond
    systemctl start yum-cron

    systemctl stop yum-cron
    systemctl stop crond

    systemctl status crond.service


    systemctl reload crond.service
    systemctl restart crond.service
    yum -y remove yum-cron
    yum -y remove cronie
    systemctl enable crond.service
    systemctl list-unit-files

    crontab -l

    crontab -e

    systemctl reload crond.service

    crontab -r原文:https://blog.51cto.com/1197822/2353529