非常简便:
crontab -e
以下是我的执行过程，输入命令后，会让我选择一个编辑器，我选的是2，因为后边写着easiest，最简单的。
liuyx@myubuntu:/$ crontab -e no crontab for liuyx - using an empty one Select an editor. To change later, run 'select-editor'. 1. /bin/ed 2. /bin/nano <---- easiest 3. /usr/bin/vim.tiny
Choose 1-3 [2]: 2 crontab: installing new crontab
选2之后会进入一个文本编辑状态，在里面根据提示，配置你要执行的任务即可：
例如我的配置：
# 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 * * * * * java -jar /home/liuyx/refreshIp/refreshIp.jar
只有最后一行是我写的，我的任务的意思是 每分钟执行一下这个jar包。五个*代表时间规则，后边的就是要执行的命令。命令这个不用说，要执行什么就写什么。时间规则是遵循cron表达式，具体请参阅cron表达式的相关写法。
配置完这些之后，记得执行一下：
sudo service cron restart
来让你的配置生效。
完毕。
也可以参阅这个：https://help.ubuntu.com/community/CronHowto