ref https://blog.csdn.net/xiangxianghehe/article/details/78149094
一.安装 crontabs服务并设置开机自启:
yum install crontabs
systemctl enable crond
systemctl start crond
systemctl stop crond
二.设置用户自定义定时任务:
vi /etc/crontab
可以看到:
# Example of job definition:
# .---------------- minute (0 - 59)
# | .------------- hour (0 - 23)
# | | .---------- day of month (1 - 31)
# | | | .------- month (1 - 12) OR jan,feb,mar,apr ...
# | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
# | | | | |
# * * * * * user-name command to be executed
即:
分钟(0-59) 小时(0-23) 日(1-31) 月(11-12) 星期(0-6,0表示周日) 用户名 要执行的命令
1
每隔30分钟root执行一次updatedb命令:
*/30 * * * * root updatedb
每天早上5点定时重启系统:
0 5 * * * root reboot
1
每隔三秒执行一次/home/somedir目录下的scripts.sh脚本:
## For excuting scripts.sh every 3 seconds##on 2014-10-15
*/1 * * * * /home/somedir/scripts.sh
*/1 * * * * sleep 3 && /home/somedir/scripts.sh
*/1 * * * * sleep 6 && /home/somedir/scripts.sh
*/1 * * * * sleep 9 && /home/somedir/scripts.sh
*/1 * * * * sleep 12 && /home/somedir/scripts.sh
*/1 * * * * sleep 15 && /home/somedir/scripts.sh
*/1 * * * * sleep 18 && /home/somedir/scripts.sh
*/1 * * * * sleep 21 && /home/somedir/scripts.sh
*/1 * * * * sleep 24 && /home/somedir/scripts.sh
*/1 * * * * sleep 27 && /home/somedir/scripts.sh
*/1 * * * * sleep 30 && /home/somedir/scripts.sh
*/1 * * * * sleep 33 && /home/somedir/scripts.sh
*/1 * * * * sleep 36 && /home/somedir/scripts.sh
*/1 * * * * sleep 39 && /home/somedir/scripts.sh
*/1 * * * * sleep 42 && /home/somedir/scripts.sh
*/1 * * * * sleep 45 && /home/somedir/scripts.sh
*/1 * * * * sleep 48 && /home/somedir/scripts.sh
*/1 * * * * sleep 51 && /home/somedir/scripts.sh
*/1 * * * * sleep 54 && /home/somedir/scripts.sh
*/1 * * * * sleep 57 && /home/somedir/scripts.sh
三.保存生效:
#加载任务,使之生效
crontab /etc/crontab
#查看任务
crontab -l
# stop
systemctl stop crond