[pkg-ntp-maintainers] Bug#832892: add minimal PPS documentation and examples

[Christian Ehrhardt]

Package: ntp
Version: 1:4.2.8p8+dfsg-1

Hi,
it is great to see that Debian enables PPS in NTP as well now.
That meant I could drop some delta that Ubuntu carried - thank you.

We also have added a few bits on documentation and examples that I'd think
would serve a Debian user just as well.
So I think it would be useful to add the following attached diff into
Debian as well.


Christian Ehrhardt
Software Engineer, Ubuntu Server
Canonical Ltd
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From 1cba7077bc30d6db4402744f73a3aa80ebacc9a1 Mon Sep 17 00:00:00 2001
From: Christian Ehrhardt <christian.ehrhardt at canonical.com>
Date: Fri, 1 Jul 2016 10:12:40 +0200
Subject: Add PPS support (LP: #1512980):

+ debian/README.Debian: Add a PPS section to the README.Debian,
  removed all PPSkit one.
+ debian/ntp.conf: Add some configuration examples from the offical
  documentation.

diff --git a/debian/README.Debian b/debian/README.Debian
index d950fb0..8638e69 100644
--- a/debian/README.Debian
+++ b/debian/README.Debian
@@ -111,6 +111,23 @@ of these keys has not yet been tested; please report success or
 failure in using them to the maintainer.
 
 
+PPS
+---
+
+This build of ntp has been pps enabled. You can use a pps reference clock,
+the default discipline is ntpd pps. On Xenial you have core_pps kernel driver
+compiled as a module per default. To achieve better accuracy, you may need to
+rebuild your kernel with CONFIG_NTP_PPS, which need CONFIG_NO_HZ=n to be
+set, you may also add CONFIG_RCU_FAST_NO_HZ.
+Be aware that if your server makes use of dhcp for its network configuration,
+you might need to check that your /etc/dhcp/dhclient.conf doesn't include any
+ntp-servers request, else your server configuration will be overriden. 
+You can find more information there:
+-https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=691672#41
+-http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#S-CONFIG-ADV-PPS
+-http://www.ntp.org/ntpfaq/NTP-s-algo-kernel.htm#Q-ALGO-KERNEL-HARDPPS
+
+
 Apparmor Profile
 ----------------
 
diff --git a/debian/ntp.conf b/debian/ntp.conf
index 207d5d5..cd75b19 100644
--- a/debian/ntp.conf
+++ b/debian/ntp.conf
@@ -55,3 +55,12 @@ restrict source notrap nomodify noquery
 # next lines.  Please do this only if you trust everybody on the network!
 #disable auth
 #broadcastclient
+
+#Changes recquired to use pps synchonisation as explained in documentation:
+#http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#AEN3918
+
+#server 127.127.8.1 mode 135 prefer    # Meinberg GPS167 with PPS
+#fudge 127.127.8.1 time1 0.0042        # relative to PPS for my hardware
+
+#server 127.127.22.1                   # ATOM(PPS)
+#fudge 127.127.22.1 flag3 1            # enable PPS API
-- 
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