我正在尝试向我的网络添加基于 GPS 的时钟源，使用发射 1-PPS 时钟脉冲的 GPS。它连接到 GPIO 引脚。
在让 ntpd 运行大约 30 分钟后，PPS 时钟仍然未被使用，并被标记为坏，但我无法弄清楚原因。
ntpq> opeer
remote local st t when poll reach delay offset disp
==============================================================================
-127.127.28.0 127.0.0.1 2 l 5 16 377 0.000 17.704 2.125
x127.127.22.0 127.0.0.1 0 l 4 16 377 0.000 6.546 0.260
+50.116.36.122 10.42.134.1 3 u 33 64 377 43.017 2.337 5.208
+52.0.56.137 10.42.134.1 3 u 33 64 377 52.022 -6.430 3.944
-2001:418:8405:4 _d58f:78d0:fd39 3 u 30 64 377 85.262 13.465 4.929
*104.156.99.30 10.42.134.1 2 u 32 64 377 63.671 -0.166 5.484
ntpq> assoc
ind assid status conf reach auth condition last_event cnt
===========================================================
1 2139 933a yes yes none outlier sys_peer 3
2 2140 9134 yes yes none falsetick reachable 3
3 2141 9424 yes yes none candidate reachable 2
4 2142 9424 yes yes none candidate reachable 2
5 2143 9324 yes yes none outlier reachable 2
6 2144 963a yes yes none sys.peer sys_peer 3
ntpq> rv 2140
associd=2140 status=9134 conf, reach, sel_falsetick, 3 events, reachable,
srcadr=127.127.22.0, srcport=123, dstadr=127.0.0.1, dstport=123, leap=00,
stratum=0, precision=-20, rootdelay=0.000, rootdisp=0.000, refid=PPS,
reftime=da584969.00b5c330 Sun, Jan 31 2016 8:50:49.002,
rec=da584969.0f2551bb Sun, Jan 31 2016 8:50:49.059, reach=377,
unreach=0, hmode=3, pmode=4, hpoll=4, ppoll=4, headway=0, flash=00 ok,
keyid=0, ttl=0, offset=9.551, delay=0.000, dispersion=0.260,
jitter=2.148,
filtdelay= 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00,
filtoffset= 9.55 9.97 10.46 10.98 11.49 11.95 12.46 12.91,
filtdisp= 0.03 0.27 0.51 0.75 0.99 1.23 1.47 1.71
PPS 源本身看起来非常干净且有规律：
# ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1454230928.995087804, sequence: 7552 - clear 0.000000000, sequence: 0
source 0 - assert 1454230929.995115719, sequence: 7553 - clear 0.000000000, sequence: 0
source 0 - assert 1454230930.995144056, sequence: 7554 - clear 0.000000000, sequence: 0
source 0 - assert 1454230931.995173388, sequence: 7555 - clear 0.000000000, sequence: 0
source 0 - assert 1454230932.995202464, sequence: 7556 - clear 0.000000000, sequence: 0
source 0 - assert 1454230933.995230660, sequence: 7557 - clear 0.000000000, sequence: 0
source 0 - assert 1454230934.995258966, sequence: 7558 - clear 0.000000000, sequence: 0
source 0 - assert 1454230935.995287693, sequence: 7559 - clear 0.000000000, sequence: 0
source 0 - assert 1454230936.995317675, sequence: 7560 - clear 0.000000000, sequence: 0
source 0 - assert 1454230937.995345684, sequence: 7561 - clear 0.000000000, sequence: 0
source 0 - assert 1454230938.995375052, sequence: 7562 - clear 0.000000000, sequence: 0
source 0 - assert 1454230939.995403851, sequence: 7563 - clear 0.000000000, sequence: 0
source 0 - assert 1454230940.995433228, sequence: 7564 - clear 0.000000000, sequence: 0
source 0 - assert 1454230941.995463497, sequence: 7565 - clear 0.000000000, sequence: 0
source 0 - assert 1454230942.995491843, sequence: 7566 - clear 0.000000000, sequence: 0
答案1
2140 被丢弃为假股票，因为它不在所选的区间内时钟选择算法。错误间隔排列，所选候选者不包括它。由于超过一半的候选者仍然保留，因此时钟被认为是正确的。
有一个为同行提供首选关键字尽管它看起来是在丢弃假股票后才适用的。
考虑在性能似乎良好的对等点上使用 ntpdate，然后使用不同的对等点重新启动 ntpd 以获得第二意见。如果它更喜欢网络对等点，并且它们的延迟和抖动相对较低，那就不算太糟糕。