[ntp:questions] SNTP server + ntpd 4.2.4 client

Dennis Hilberg, Jr. timekeeper at dennishilberg.com.invalid
Mon Mar 17 16:44:45 UTC 2008

Unruh wrote:
>> My system is running a Linux kernel patched with real-time support.
>> I don't feel confident applying the PPS support patch on top of it.
> No need. Just attach the gps as a refclock. The kernel does not need pps
> support to use the refclock.

The Linux kernel does not have built-in PPS support, so yes he would have to 
patch and recompile the kernel in order to use the PPS provided by the GPS 
device. Otherwise it will just be using NMEA time, which is not very 
accurate for timing purposes. For Linux 2.4 there is the PPSkit, and for 
Linux 2.6 there is LinuxPPS.

Instead you can use the shmpps driver to use the PPS signal without patching 
the Linux kernel. I use it and it works very well.

FreeBSD has built-in PPS support (no patch needed), but it's not enabled by 
default. PPS support has to be enabled in the kernel config and the kernel 


Dennis Hilberg, Jr.     \  timekeeper(at)dennishilberg(dot)com
NTP Server Information:  \  http://saturn.dennishilberg.com/ntp.php

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