Question & Answer
Question
How can I keep the hardware clock synchronized with system time when NTP is being used?
Answer
The /etc/sysconfig/ntpd file contains the SYNC_HW CLOCK setting which determines if the hardware clock updates every time NTP synchronizes the system time. By default, the setting is off as shown below:
SYNC_HWCLOCK=no
To have the hardware clock updated every time NTP successfully synchronizes the system time with a time server, modify the line to read as follows:
SYNC_HWCLOCK=yes
In addition, you may also want to update the clock every time the NTP daemon service is started. To do this, edit the /etc/sysconfig/ntpd file and modify the OPTIONS line.
It will look similar to the following:
OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"
Add ' -x ' to the end of this parameter so that it reads as follows:
OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid -x"
The next time you restart the NTP daemon, you will see the following:
# service ntpd restart
Shutting down ntpd: [ OK ]
ntpd: Synchronizing with time server: [ OK ]
Syncing hardware clock to system time [ OK ]
Starting ntpd: [ OK ]
You can confirm the two times are in synch with the following command:
hwclock --show ; date
Note that in the sample output, the first line of output is the hardware clock's current time and the second line is the system's current time:
[root]# hwclock --show ; date
Fri 02 Oct 2009 01:37:20 AM EDT -0.664685 seconds
Fri Oct 2 01:37:19 EDT 2009
Historical Number
NZ025708
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Document Information
More support for:
IBM PureData System
Software version:
1.0.0
Document number:
464665
Modified date:
17 October 2019
UID
swg21572558