# 安装crontab
yum install cronie -y

# 启动
service crond start
# 停止
service crond stop
# 重启
service crond restart
# 运行状态
service crond status
# 重新载入配置
service crond reload

# 启动
systemctl start crond
# 停止
systemctl stop crond
# 重启
systemctl restart crond
# 运行状态
systemctl status crond
# 开机启动
systemctl enable crond

# 编辑该用户的定时器配置
crontab -e
# 列出该用户的计时器设置
crontab -l
# 删除该用户的计时器设置
crontab -r
# 指定要设定计时器的用户名称
crontab -u xujun

# 查看定时脚本
vi /etc/crontab

# 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

# 定时备份数据库(凌晨2点)
0 2 * * * root /data1/mysql/bak/bak.sh > /data1/mysql/bak/bak.log 2>&1

# 查看运行日志
tail -f /var/log/cron