[time-nuts] FreeBSD version

[Magnus Danielson]

Adam,

Adam Feigin wrote:
>> I guess this might be a little ot for this thread but maybe not.  I'm
>> a newbie to all of this stuff but judging from the archives freebsd
>> seems to be the OS of choice for these highly accurate NTP servers.
>> Why is the case?  Is there something specific to it that makes it more
>> suitable for this application than say some of the other BSD's or
>> Linux?
>>   
> 
> Well, FreeBSD had one of the earliest PPSAPI implementations, so its
> well tested, and it works extremely well.
> 
> Linux still does not have a PPSAPI implementation in the "standard"
> kernel. As of 2.6.31, its sort of kinda of halfway there, but not
> completely, and I've never been able to get it to work. I'm sure one
> can, if ones time in not very valuable.

Actually, one problem is that glibc is (was?) publishing an older 
variant of the PPSAPI than the kernel actually supports. This is due to 
an unfortunate decission to let kernel-API being made available directly 
to be used by applications be declared by glibc rather than following 
the kernel. The NTPD finds the glibc variant of the header and uses the 
older interface version regardless of the fact that the kernel has 
advanced since the glibc took its snapshot out of the early 2.x series.

The correct way would be either to let glibc discover the actual kernel 
abilites or just provide the kernel-call wrappers and let the kernel 
provide the actual header file.

Usually the glibc approach is correct, but for PPSAPI it is not. 
Updating glibc to the current version heals puts a japanese paper wall 
in front of the problem, but you haven't properly healed the wound.

> FreeBSD works right out of the box (okay, you'll need to add the PPS
> option to the kernel configuration).

To a higher degree things are integrated there in this respect.

Cheers,
Magnus