【CentOS-7.4】crontab

# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 
# For more information see the manual pages of crontab(5) and cron(8)
# 
# m h  dom mon dow   command

5	3	*	*	*	yum upgrade -y

10      3       *       *       *       yum update -y

15      3       *       *       *       yum upgrade -y

20      3       *       *       *       yum update -y

25     	3       *       *       *       yum clean