Moxa DA-682A-C7-DPP [11/108] Setting the system clock and the rtc

DA-682A-DPP Linux Software Software Configuration

2-5

Setting the System Clock and the RTC

The DA-682A-DPP-LX uses two clocks to keep time; one is the system time, and the other is the time provided

by the RTC (Real Time Clock) built into the DA-682A-DPP’s hardware. The system clock is set using the date

command, and the RTC is set using the hwclock command.

WARNING

The RTC time setting on your computer is not in synch with the current time if

the f

ile system check (fsck) utility

shows

the following error on boot up:

Supberblock last mou

nt time (Tue Dec 15 12:00:00 2015) is in the future. UNEXPECTED INCONSISTENCY;

RUN fsck MANUALLY.

To prevent this issue from occuring at the next boot up, synchonize the

system BIOS time with the current

time.

NTP Client

The DA-682A-DPP-LX comes with a built-in Network Time Protocol (NTP) client that can access remote NTP

servers to synchronize your system clock to worldwide reference clocks. To synchronize the system time to a

remote reference clock, use the ntpdate command:

moxa@Moxa:~#sudo ntpdate time.stdtime.gov.tw

Next, set the RTC using the hwclock command:

moxa@Moxa:~#sudo hwclock –w

ATTENTION

Before using the NTP client utility, check your IP address and network settings (gateway and DNS) to make

sure an In

ternet connection is available. For additional information on using NTP (Network Time Protocol

), visit

the project’s home

page at:

http://www.ntp.org

Using a Shell Script for Automatic Updates

As the RTC gets older, it might run slower and fail to accurately track time. This section provides one example

of how a shell script can be used to repeatedly synchronize the RTC to the system clock by using the Linux

initialization table (inittab). Because the system clock will be automatically synched using NTP, the two clocks

will reliably keep time. Other methods are also available, for instance using cron (see the section “Cron for

Executing Scheduled Commands”) or using the at command. The example below shows how to write a simple

shell script for keeping the two clocks synchronized, and how to set the system to continuously run the script

in the background, across sysystem re-boots.