创建crontab任务
参考：https://www.cnblogs.com/Icanflyssj/p/5138851.html
3. crontab常用的几个命令格式
crontab -l //显示用户的crontab文件的内容
crontab -e //编辑用户的crontab文件的内容
crontab -r //删除用户的crontab文件
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在第一次使用crontab -e，会要求选择编辑器，我选择是vim.basic
编辑文件，内容如下
root@ubuntu:/var/log# crontab -e # Edit this file to introduce tasks to be run by cron. # # Each task to run has to be defined through a single line # indicating with different fields when the task will be run # and what command to run for the task # # To define the time you can provide concrete values for # minute (m), hour (h), day of month (dom), month (mon), # and day of week (dow) or use '*' in these fields (for 'any').# # Notice that tasks will be started based on the cron's system # daemon's notion of time and timezones. # # Output of the crontab jobs (including errors) is sent through # email to the user the crontab file belongs to (unless redirected). # # 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 * * * * * /home/xwdreamer/eclipse-workspace/RELEASED_V2_10_20180331/iotkit-embedded/output/release/bin/linkkit-example
日志服务
参考：https://blog.csdn.net/ggz631047367/article/details/50185425
ubuntu默认没有开启cron日志记录
1. 修改rsyslog
sudo vim /etc/rsyslog.d/50-default.conf
cron.* /var/log/cron.log #将cron前面的注释符去掉
2.重启rsyslog
sudo service rsyslog restart
3.查看crontab日志
less /var/log/cron.log
注意：这里必须重启日志服务，重启以后使用less查看可能还没有日志，需要等任务执行以后才能看到日志。