Moxa ioPAC 8500-5-M12-C-T [37/69] Moxa c programmable rtu controllers managing the rtu controllers

Moxa C Programmable RTU Controllers Managing the RTU Controllers

3-7

Executing Scheduled Commands with Cron

Daemon

Start Cron from the directory /etc/rc.d/rc. local. It will return immediately without adding a ‘&’ to run in the

background.

The Cron daemon will search /etc/cron.d/crontab for crontab files, which are named after accounts in

/etc/passwd.

Cron wakes up every minute, and checks each command to see if it should be run in that minute. Modify the file

/etc/cron.d/crontab to set up the scheduled applications. Crontab files are in the following formats:

mm h dom mon dow user command

min hour date month week user command

0-59 0-23 1-31 1-12 0-6 (0 is Sunday)

The following example demonstrates how to use Cron.

How to use Cron to update the system time and RTC time every day at 8:00.

STEP1: Write a shell script named fixtime.sh and save it to /home/.

#!/bin/sh

ntpdate time.nist.gov

hwclock –-systohc

exit 0

STEP2: Change mode of fixtime.sh

#chmod 755 fixtime.sh

STEP3: Modify /etc/cron.d/crontab file to run fixtime.sh at 8:00 every day.

Add the following line to the end of crontab:

* 8 * * * root/homefixtime.sh

STEP4: Enable the cron daemon manually.

#/etc/init.d/cron start

STEP5: Enable Cron when the system boots up.

Add the following line in the file /etc/init.d/rc.local.

#/etc/init.d/cron start