service cron restart命令报错如下：
stop: Rejected send message, 1 matched rules; type="method_call", sender=":1.121" (uid=1000 pid=25347 comm="stop cron ") interface="com.ubuntu.Upstart0_6.Job" member="Stop" error name="(unset)" requested_reply="0" destination="com.ubuntu.Upstart" (uid=0 pid=1 comm="/sbin/init ")
start: Rejected send message, 1 matched rules; type="method_call", sender=":1.122" (uid=1000 pid=25341 comm="start cron ") interface="com.ubuntu.Upstart0_6.Job" member="Start" error name="(unset)" requested_reply="0" destination="com.ubuntu.Upstart" (uid=0 pid=1 comm="/sbin/init ")
解决办法：
需要root权限才可以正常运行