1ntpd(8)                          User Commands                         ntpd(8)
2
3
4

NAME

6       ntpd - NTP daemon program
7

SYNOPSIS

9       ntpd  [-flags]  [-flag [value]] [--option-name[[=| ]value]] [ <server1>
10       ... <serverN> ]
11
12

DESCRIPTION

14       The ntpd utility is an operating system daemon which sets and maintains
15       the  system  time  of  day  in  synchronism with Internet standard time
16       servers.  It is a complete implementation of the Network Time  Protocol
17       (NTP) version 4, as defined by RFC-5905, but also retains compatibility
18       with version 3, as defined by  RFC-1305,  and  versions  1  and  2,  as
19       defined by RFC-1059 and RFC-1119, respectively.
20
21       The ntpd utility does most computations in 64-bit floating point arith‐
22       metic and does relatively clumsy 64-bit  fixed  point  operations  only
23       when  necessary  to preserve the ultimate precision, about 232 picosec‐
24       onds.  While the ultimate precision is  not  achievable  with  ordinary
25       workstations  and  networks  of  today,  it may be required with future
26       gigahertz CPU clocks and gigabit LANs.
27
28       Ordinarily, ntpd reads the ntp.conf(5) configuration  file  at  startup
29       time  in  order  to determine the synchronization sources and operating
30       modes.  It is also possible to specify  a  working,  although  limited,
31       configuration  entirely  on  the command line, obviating the need for a
32       configuration file.  This may be particularly  useful  when  the  local
33       host  is  to  be  configured  as a broadcast/multicast client, with all
34       peers being determined by listening to broadcasts at run time.
35
36       If NetInfo support is built into ntpd, then ntpd will attempt  to  read
37       its configuration from the NetInfo if the default ntp.conf(5) file can‐
38       not be read and no file is specified by the -c option.
39
40       Various internal ntpd variables  can  be  displayed  and  configuration
41       options  altered  while  the  ntpd  is  running  using  the ntpq(8) and
42       ntpdc(8) utility programs.
43
44       When ntpd starts it looks at the value of umask(2), and  if  zero  ntpd
45       will set the umask(2) to 022.
46

OPTIONS

48       -4, --ipv4
49              Force  IPv4 DNS name resolution.  This option must not appear in
50              combination with any of the following options: ipv6.
51
52              Force DNS resolution of following host names on the command line
53              to the IPv4 namespace.
54
55       -6, --ipv6
56              Force  IPv6 DNS name resolution.  This option must not appear in
57              combination with any of the following options: ipv4.
58
59              Force DNS resolution of following host names on the command line
60              to the IPv6 namespace.
61
62       -a, --authreq
63              Require  crypto  authentication.  This option must not appear in
64              combination with any of the following options: authnoreq.
65
66              Require cryptographic authentication for broadcast client,  mul‐
67              ticast  client  and symmetric passive associations.  This is the
68              default.
69
70       -A, --authnoreq
71              Do not require crypto  authentication.   This  option  must  not
72              appear  in  combination  with  any  of  the  following  options:
73              authreq.
74
75              Do  not  require  cryptographic  authentication  for   broadcast
76              client,  multicast  client  and  symmetric passive associations.
77              This is almost never a good idea.
78
79       -b, --bcastsync
80              Allow us to sync to broadcast servers.
81
82
83       -c string, --configfile=string
84              configuration file name.
85
86              The name and path of the configuration  file,  /etc/ntp.conf  by
87              default.
88
89       -d, --debug-level
90              Increase  debug  verbosity  level.   This  option  may appear an
91              unlimited number of times.
92
93
94       -D number, --set-debug-level=number
95              Set the debug verbosity level.  This option may appear an unlim‐
96              ited  number  of  times.  This option takes an integer number as
97              its argument.
98
99
100       -f string, --driftfile=string
101              frequency drift file name.
102
103              The name and path  of  the  frequency  file,  /etc/ntp.drift  by
104              default.   This is the same operation as the driftfile driftfile
105              configuration specification in the /etc/ntp.conf file.
106
107       -g, --panicgate
108              Allow the first adjustment to be Big.  This option may appear an
109              unlimited number of times.
110
111              Normally,  ntpd  exits  with  a message to the system log if the
112              offset exceeds the panic threshold, which is 1000 s by  default.
113              This  option  allows  the  time  to  be set to any value without
114              restriction; however, this can happen only once. If the  thresh‐
115              old is exceeded after that, ntpd will exit with a message to the
116              system log. This option can be used with the -q and -x  options.
117              See the tinker configuration file directive for other options.
118
119       -G, --force-step-once
120              Step any initial offset correction..
121
122              Normally,  ntpd  steps  the  time if the time offset exceeds the
123              step threshold, which is 128 ms by default, and otherwise  slews
124              the  time.   This option forces the initial offset correction to
125              be stepped,  so  the  highest  time  accuracy  can  be  achieved
126              quickly.   However,  this  may also cause the time to be stepped
127              back so this option must not be used if  applications  requiring
128              monotonic  time  are running.  See the tinker configuration file
129              directive for other options.
130
131       -i string, --jaildir=string
132              Jail directory.
133
134              Chroot the server to the  directory  jaildir  This  option  also
135              implies  that  the  server  attempts  to drop root privileges at
136              startup.  You may need to also specify a -u option.  This option
137              is only available if the OS supports adjusting the clock without
138              full root privileges.  This option  is  supported  under  NetBSD
139              (configure  with  --enable-clockctl)  or  Linux  (configure with
140              --enable-linuxcaps) or Solaris (configure  with  --enable-solar‐
141              isprivs).
142
143       -I iface, --interface=iface
144              Listen  on an interface name or address.  This option may appear
145              an unlimited number of times.
146
147              Open the network address given, or all the addresses  associated
148              with  the given interface name.  This option may appear multiple
149              times.  This option also implies not  opening  other  addresses,
150              except  wildcard  and  localhost.   This  option  is deprecated.
151              Please consider using the configuration file interface  command,
152              which is more versatile.
153
154       -k string, --keyfile=string
155              path to symmetric keys.
156
157              Specify   the   name   and  path  of  the  symmetric  key  file.
158              /etc/ntp.keys is the default.  This is the same operation as the
159              keys keyfile configuration file directive.
160
161       -l string, --logfile=string
162              path to the log file.
163
164              Specify  the  name and path of the log file.  The default is the
165              system log file.  This is the same operation as the logfile log‐
166              file configuration file directive.
167
168       -L, --novirtualips
169              Do not listen to virtual interfaces.
170
171              Do not listen to virtual interfaces, defined as those with names
172              containing a colon.  This option is deprecated.  Please consider
173              using  the  configuration  file interface command, which is more
174              versatile.
175
176       -M, --modifymmtimer
177              Modify Multimedia Timer (Windows only).
178
179              Set the Windows Multimedia Timer to  highest  resolution.   This
180              ensures  the  resolution  does not change while ntpd is running,
181              avoiding timekeeping glitches associated with changes.
182
183       -n, --nofork
184              Do not fork.  This option must not appear  in  combination  with
185              any of the following options: wait-sync.
186
187
188       -N, --nice
189              Run at high priority.
190
191              To the extent permitted by the operating system, run ntpd at the
192              highest priority.
193
194       -p string, --pidfile=string
195              path to the PID file.
196
197              Specify the name and path of the  file  used  to  record  ntpd's
198              process  ID.   This is the same operation as the pidfile pidfile
199              configuration file directive.
200
201       -P number, --priority=number
202              Process priority.  This option takes an integer  number  as  its
203              argument.
204
205              To the extent permitted by the operating system, run ntpd at the
206              specified sched_setscheduler(SCHED_FIFO) priority.
207
208       -q, --quit
209              Set the time and quit.  This option must not appear in  combina‐
210              tion  with  any  of the following options: saveconfigquit, wait-
211              sync.
212
213              ntpd will not daemonize and will exit after the clock  is  first
214              synchronized.  This behavior mimics that of the ntpdate program,
215              which will soon be replaced with a shell script.  The -g and  -x
216              options  can  be  used  with this option.  Note: The kernel time
217              discipline is disabled with this option.
218
219       -r string, --propagationdelay=string
220              Broadcast/propagation delay.
221
222              Specify the default propagation delay from the  broadcast/multi‐
223              cast  server to this client. This is necessary only if the delay
224              cannot be computed automatically by the protocol.
225
226       --saveconfigquit=string
227              Save parsed configuration and quit.  This option must not appear
228              in  combination  with  any of the following options: quit, wait-
229              sync.
230
231              Cause ntpd to parse its startup configuration file and  save  an
232              equivalent  to  the  given  filename  and exit.  This option was
233              designed for automated testing.
234
235       -s string, --statsdir=string
236              Statistics file location.
237
238              Specify the directory path for files created by  the  statistics
239              facility.   This  is the same operation as the statsdir statsdir
240              configuration file directive.
241
242       -t tkey, --trustedkey=tkey
243              Trusted key number.  This option may appear an unlimited  number
244              of times.
245
246              Add the specified key number to the trusted key list.
247
248       -u string, --user=string
249              Run as userid (or userid:groupid).
250
251              Specify  a  user,  and  optionally  a group, to switch to.  This
252              option is only available if the OS supports adjusting the  clock
253              without  full  root  privileges.  This option is supported under
254              NetBSD (configure with --enable-clockctl)  or  Linux  (configure
255              with  --enable-linuxcaps)  or  Solaris (configure with --enable-
256              solarisprivs).
257
258       -U number, --updateinterval=number
259              interval in seconds between scans for new or dropped interfaces.
260              This option takes an integer number as its argument.
261
262              Give  the  time  in seconds between two scans for new or dropped
263              interfaces.  For systems with routing socket support  the  scans
264              will  be  performed  shortly after the interface change has been
265              detected by the system.  Use 0 to disable scanning.  60  seconds
266              is the minimum time between scans.
267
268       --var=nvar
269              make ARG an ntp variable (RW).  This option may appear an unlim‐
270              ited number of times.
271
272
273       --dvar=ndvar
274              make ARG an ntp variable (RW|DEF).  This option  may  appear  an
275              unlimited number of times.
276
277
278       -w number, --wait-sync=number
279              Seconds  to  wait  for  first  clock sync.  This option must not
280              appear in combination with any of the following options: nofork,
281              quit,  saveconfigquit.   This  option takes an integer number as
282              its argument.
283
284              If greater than zero, alters ntpd's  behavior  when  forking  to
285              daemonize.   Instead  of exiting with status 0 immediately after
286              the fork, the parent waits up to the specified number of seconds
287              for  the  child to first synchronize the clock.  The exit status
288              is zero (success) if the clock was synchronized, otherwise it is
289              ETIMEDOUT.   This provides the option for a script starting ntpd
290              to easily wait for the first set of the clock before proceeding.
291
292       -x, --slew
293              Slew up to 600 seconds.
294
295              Normally, the time is slewed if the offset is less than the step
296              threshold,  which is 128 ms by default, and stepped if above the
297              threshold.  This option sets the threshold to 600  s,  which  is
298              well  within  the  accuracy  window  to  set the clock manually.
299              Note: Since the slew rate of typical Unix kernels is limited  to
300              0.5  ms/s,  each  second  of adjustment requires an amortization
301              interval of 2000 s.  Thus, an adjustment as much as 600  s  will
302              take  almost  14 days to complete.  This option can be used with
303              the -g and -q options.  See the tinker configuration file direc‐
304              tive  for  other  options.   Note: The kernel time discipline is
305              disabled with this option.
306
307       --usepcc
308              Use CPU cycle counter (Windows only).
309
310              Attempt to substitute  the  CPU  counter  for  QueryPerformance‐
311              Counter.   The  CPU counter and QueryPerformanceCounter are com‐
312              pared, and if they have the  same  frequency,  the  CPU  counter
313              (RDTSC on x86) is used directly, saving the overhead of a system
314              call.
315
316       --pccfreq=string
317              Force CPU cycle counter use (Windows only).
318
319              Force substitution the CPU counter for  QueryPerformanceCounter.
320              The  CPU counter (RDTSC on x86) is used unconditionally with the
321              given frequency (in Hz).
322
323       -m, --mdns
324              Register with mDNS as a NTP server.
325
326              Registers as an NTP server with  the  local  mDNS  server  which
327              allows the server to be discovered via mDNS client lookup.
328
329       -?, --help
330              Display usage information and exit.
331
332       -!, --more-help
333              Pass the extended usage information through a pager.
334
335       --version [{v|c|n}]
336              Output  version of program and exit.  The default mode is `v', a
337              simple version.  The `c' mode will print  copyright  information
338              and `n' will print the full copyright notice.
339

OPTION PRESETS

341       Any option that is not marked as not presettable may be preset by load‐
342       ing values from environment variables named:
343         NTPD_<option-name> or NTPD
344

USAGE

346   How NTP Operates
347       The ntpd utility operates by exchanging messages with one or more  con‐
348       figured  servers  over  a  range  of  designated  poll intervals.  When
349       started, whether  for  the  first  or  subsequent  times,  the  program
350       requires  several  exchanges  from the majority of these servers so the
351       signal processing and mitigation algorithms can  accumulate  and  groom
352       the  data  and  set  the  clock.   In order to protect the network from
353       bursts, the initial poll interval for each server is delayed an  inter‐
354       val  randomized over a few seconds.  At the default initial poll inter‐
355       val of 64s, several minutes can elapse before the clock is  set.   This
356       initial  delay  to set the clock can be safely and dramatically reduced
357       using the iburst keyword with  the  server  configuration  command,  as
358       described in ntp.conf(5).
359
360       Most operating systems and hardware of today incorporate a time-of-year
361       (TOY) chip to maintain the time during periods when the power  is  off.
362       When  the machine is booted, the chip is used to initialize the operat‐
363       ing system time.  After the machine has synchronized to a  NTP  server,
364       the  operating  system  corrects  the  chip  from time to time.  In the
365       default case, if ntpd detects that the time on the host  is  more  than
366       1000s  from  the  server  time, ntpd assumes something must be terribly
367       wrong and the only reliable action is for the operator to intervene and
368       set the clock by hand.  (Reasons for this include there is no TOY chip,
369       or its battery is dead, or that the TOY chip is just of poor  quality.)
370       This  causes  ntpd to exit with a panic message to the system log.  The
371       -g option overrides this check and the clock will be set to the  server
372       time  regardless of the chip time (up to 68 years in the past or future
373       — this is a limitation of the NTPv4 protocol).  However, and to protect
374       against  broken  hardware,  such  as when the CMOS battery fails or the
375       clock counter becomes defective, once the clock has been set  an  error
376       greater than 1000s will cause ntpd to exit anyway.
377
378       Under  ordinary  conditions,  ntpd  adjusts the clock in small steps so
379       that the timescale is effectively continuous  and  without  discontinu‐
380       ities.   Under  conditions of extreme network congestion, the roundtrip
381       delay jitter can exceed three seconds and the synchronization distance,
382       which is equal to one-half the roundtrip delay plus error budget terms,
383       can become very large.  The  ntpd  algorithms  discard  sample  offsets
384       exceeding  128 ms, unless the interval during which no sample offset is
385       less than 128 ms exceeds 900s.  The first sample after that, no  matter
386       what  the  offset,  steps the clock to the indicated time.  In practice
387       this reduces the false alarm rate where the clock is stepped  in  error
388       to a vanishingly low incidence.
389
390       As  the  result  of  this behavior, once the clock has been set it very
391       rarely strays more than 128 ms even under extreme cases of network path
392       congestion  and  jitter.   Sometimes,  in particular when ntpd is first
393       started without a valid drift file on a system with a  large  intrinsic
394       drift  the  error  might  grow  to exceed 128 ms, which would cause the
395       clock to be set backwards if the local clock time is more than 128 s in
396       the future relative to the server.  In some applications, this behavior
397       may be unacceptable.  There are several solutions, however.  If the  -x
398       option is included on the command line, the clock will never be stepped
399       and only slew corrections will be used.  But this choice comes  with  a
400       cost  that  should  be carefully explored before deciding to use the -x
401       option.  The maximum slew rate possible is limited  to  500  parts-per-
402       million  (PPM)  as a consequence of the correctness principles on which
403       the NTP protocol and algorithm design are  based.   As  a  result,  the
404       local  clock  can take a long time to converge to an acceptable offset,
405       about 2,000 s for each second  the  clock  is  outside  the  acceptable
406       range.   During  this  interval  the local clock will not be consistent
407       with any other network clock and the system cannot be used for distrib‐
408       uted applications that require correctly synchronized network time.
409
410       In  spite  of  the  above  precautions,  sometimes when large frequency
411       errors are present the resulting time offsets stray outside the  128-ms
412       range  and  an  eventual  step or slew time correction is required.  If
413       following such a correction the frequency error is so  large  that  the
414       first  sample  is  outside  the  acceptable range, ntpd enters the same
415       state as when the ntp.drift file is not present.  The  intent  of  this
416       behavior  is  to quickly correct the frequency and restore operation to
417       the normal  tracking  mode.   In  the  most  extreme  cases  (the  host
418       time.ien.it  comes  to mind), there may be occasional step/slew correc‐
419       tions and subsequent frequency corrections.  It helps in these cases to
420       use  the  burst  keyword when configuring the server, but ONLY when you
421       have permission to do so from the owner of the target host.
422
423       Finally, in the past many  startup  scripts  would  run  ntpdate(8)  or
424       sntp(8)  to  get  the  system  clock  close  to correct before starting
425       ntpd(8), but this was never more than a mediocre hack and is no  longer
426       needed.   If  you  are following the instructions in Starting NTP (Best
427       Current Practice) and you still need to  set  the  system  time  before
428       starting  ntpd, please open a bug report and document what is going on,
429       and then look at using sntp(8) if you really  need  to  set  the  clock
430       before starting ntpd.
431
432       There  is  a way to start ntpd(8) that often addresses all of the prob‐
433       lems mentioned above.
434
435   Starting NTP (Best Current Practice)
436       First, use the iburst option on your server entries.
437
438       If you can also keep a good ntp.drift file  then  ntpd(8)  will  effec‐
439       tively  "warm-start" and your system's clock will be stable in under 11
440       seconds' time.
441
442       As soon as possible in the startup  sequence,  start  ntpd(8)  with  at
443       least  the -g and perhaps the -N options.  Then, start the rest of your
444       "normal" processes.  This will give ntpd(8) as much time as possible to
445       get the system's clock synchronized and stable.
446
447       Finally,  if  you  have processes like dovecot or database servers that
448       require monotonically-increasing time, run ntp-wait(8) as late as  pos‐
449       sible  in  the  boot sequence (perhaps with the -v flag) and after ntp-
450       wait(8) exits successfully it is as safe as it will ever  be  to  start
451       any process that require stable time.
452
453   Frequency Discipline
454       The  ntpd  behavior  at  startup depends on whether the frequency file,
455       usually ntp.drift, exists.  This file contains the latest  estimate  of
456       clock  frequency error.  When the ntpd is started and the file does not
457       exist, the ntpd enters a special mode designed to quickly adapt to  the
458       particular  system  clock  oscillator  time  and frequency error.  This
459       takes approximately 15 minutes, after which the time and frequency  are
460       set  to  nominal values and the ntpd enters normal mode, where the time
461       and frequency are continuously tracked relative to the  server.   After
462       one hour the frequency file is created and the current frequency offset
463       written to it.  When the ntpd is started and the file does  exist,  the
464       ntpd  frequency  is  initialized  from  the file and enters normal mode
465       immediately.  After that the current frequency offset is written to the
466       file at hourly intervals.
467
468   Operating Modes
469       The ntpd utility can operate in any of several modes, including symmet‐
470       ric active/passive, client/server broadcast/multicast and manycast,  as
471       described  in  the  "Association Management" page (available as part of
472       the HTML documentation provided in  /usr/share/doc/ntp).   It  normally
473       operates  continuously  while monitoring for small changes in frequency
474       and trimming the clock for the ultimate  precision.   However,  it  can
475       operate  in  a  one-time  mode  where  the time is set from an external
476       server and frequency is set from a previously recorded frequency  file.
477       A  broadcast/multicast  or manycast client can discover remote servers,
478       compute server-client propagation delay correction factors and  config‐
479       ure  itself automatically.  This makes it possible to deploy a fleet of
480       workstations without specifying configuration details specific  to  the
481       local environment.
482
483       By default, ntpd runs in continuous mode where each of possibly several
484       external servers is polled at  intervals  determined  by  an  intricate
485       state  machine.   The  state  machine measures the incidental roundtrip
486       delay jitter and oscillator frequency wander and  determines  the  best
487       poll  interval  using  a  heuristic algorithm.  Ordinarily, and in most
488       operating environments, the state machine will start with 64s intervals
489       and  eventually  increase  in steps to 1024s.  A small amount of random
490       variation is introduced in order to avoid bunching at the servers.   In
491       addition,  should  a  server become unreachable for some time, the poll
492       interval is increased in steps to 1024s  in  order  to  reduce  network
493       overhead.
494
495       In  some cases it may not be practical for ntpd to run continuously.  A
496       common workaround has been to run the ntpdate(8)  or  sntp(8)  programs
497       from a cron(8) job at designated times.  However, these programs do not
498       have the crafted signal processing, error checking or mitigation  algo‐
499       rithms  of  ntpd.  The -q option is intended for this purpose.  Setting
500       this option will cause ntpd to exit just after setting  the  clock  for
501       the  first  time.  The procedure for initially setting the clock is the
502       same as in continuous mode; most applications  will  probably  want  to
503       specify the iburst keyword with the server configuration command.  With
504       this keyword a volley of messages are exchanged to groom the  data  and
505       the  clock is set in about 10 s.  If nothing is heard after a couple of
506       minutes, the daemon times out and exits.  After a  suitable  period  of
507       mourning, the ntpdate(8) program will be retired.
508
509       When  kernel  support  is  available to discipline the clock frequency,
510       which is the case for stock Solaris, Tru64, Linux and FreeBSD, a useful
511       feature is available to discipline the clock frequency.  First, ntpd is
512       run in continuous mode with selected servers in order  to  measure  and
513       record  the intrinsic clock frequency offset in the frequency file.  It
514       may take some hours for the frequency and offset to settle down.   Then
515       the  ntpd  is  stopped  and  run in one-time mode as required.  At each
516       startup, the frequency is read from the file and initializes the kernel
517       frequency.
518
519   Poll Interval Control
520       This  version  of NTP includes an intricate state machine to reduce the
521       network load while maintaining a quality of synchronization  consistent
522       with  the  observed  jitter  and wander.  There are a number of ways to
523       tailor the operation in order enhance accuracy by reducing the interval
524       or  to  reduce network overhead by increasing it.  However, the user is
525       advised to carefully consider the consequences  of  changing  the  poll
526       adjustment  range from the default minimum of 64 s to the default maxi‐
527       mum of 1,024 s.  The default minimum can be  changed  with  the  tinker
528       minpoll  command to a value not less than 16 s.  This value is used for
529       all configured associations, unless overridden by the minpoll option on
530       the  configuration  command.   Note  that  most device drivers will not
531       operate properly if the poll interval is less than 64 s  and  that  the
532       broadcast  server  and  manycast  client associations will also use the
533       default, unless overridden.
534
535       In some cases involving dial up or toll services, it may be  useful  to
536       increase  the  minimum  interval  to  a few tens of minutes and maximum
537       interval to a day or so.  Under normal operation conditions,  once  the
538       clock  discipline loop has stabilized the interval will be increased in
539       steps from the minimum to  the  maximum.   However,  this  assumes  the
540       intrinsic clock frequency error is small enough for the discipline loop
541       correct it.  The capture range of the loop is 500 PPM at an interval of
542       64s  decreasing by a factor of two for each doubling of interval.  At a
543       minimum of 1,024 s, for example, the capture range is only 31 PPM.   If
544       the intrinsic error is greater than this, the drift file ntp.drift will
545       have to be specially tailored to reduce the residual error  below  this
546       limit.  Once this is done, the drift file is automatically updated once
547       per hour and is available to initialize  the  frequency  on  subsequent
548       daemon restarts.
549
550   The huff-n'-puff Filter
551       In  scenarios  where a considerable amount of data are to be downloaded
552       or uploaded over telephone modems, timekeeping quality can be seriously
553       degraded.   This  occurs  because  the  differential  delays on the two
554       directions of transmission can be  quite  large.   In  many  cases  the
555       apparent time errors are so large as to exceed the step threshold and a
556       step correction can occur during and after  the  data  transfer  is  in
557       progress.
558
559       The huff-n'-puff filter is designed to correct the apparent time offset
560       in these cases.  It depends on knowledge of the propagation delay  when
561       no  other  traffic  is present.  In common scenarios this occurs during
562       other than work hours.  The filter  maintains  a  shift  register  that
563       remembers the minimum delay over the most recent interval measured usu‐
564       ally in hours.  Under conditions of severe delay, the  filter  corrects
565       the  apparent  offset  using  the sign of the offset and the difference
566       between the apparent delay and minimum delay.  The name of  the  filter
567       reflects  the  negative  (huff)  and  positive (puff) correction, which
568       depends on the sign of the offset.
569
570       The filter is activated by the tinker command and huffpuff keyword,  as
571       described in ntp.conf(5).
572

ENVIRONMENT

574       See OPTION PRESETS for configuration environment variables.
575

FILES

577       /etc/ntp.conf  the default name of the configuration file
578       /etc/ntp.drift the default name of the drift file
579       /etc/ntp.keys  the default name of the key file
580

EXIT STATUS

582       One of the following exit values will be returned:
583
584       0  (EXIT_SUCCESS)
585              Successful program execution.
586
587       1  (EXIT_FAILURE)
588              The operation failed or the command syntax was not valid.
589
590       70  (EX_SOFTWARE)
591              libopts  had an internal operational error.  Please report it to
592              autogen-users@lists.sourceforge.net.  Thank you.
593

SEE ALSO

595       ntp.conf(5), ntpdate(8), ntpdc(8), ntpq(8), sntp(8)
596
597       In addition to the manual pages provided,  comprehensive  documentation
598       is  available on the world wide web at http://www.ntp.org/.  A snapshot
599       of   this   documentation   is   available   in    HTML    format    in
600       /usr/share/doc/ntp.  David L. Mills, Network Time Protocol (Version 1),
601       RFC1059
602
603       David L. Mills, Network Time Protocol (Version 2), RFC1119
604
605       David L. Mills, Network Time Protocol (Version 3), RFC1305
606
607       David L. Mills and J. Martin, Ed. and J. Burbank and W. Kasch,  Network
608       Time Protocol Version 4: Protocol and Algorithms Specification, RFC5905
609
610       David  L.  Mills and B. Haberman, Ed., Network Time Protocol Version 4:
611       Autokey Specification, RFC5906
612
613       H. Gerstung and C. Elliott and B. Haberman, Ed., Definitions of Managed
614       Objects for Network Time Protocol Version 4: (NTPv4), RFC5907
615
616       R.  Gayraud and B. Lourdelet, Network Time Protocol (NTP) Server Option
617       for DHCPv6, RFC5908
618

AUTHORS

620       The University of Delaware and Network Time Foundation
621
623       Copyright (C) 1992-2020 The University of  Delaware  and  Network  Time
624       Foundation  all  rights  reserved.   This program is released under the
625       terms of the NTP license, <http://ntp.org/license>.
626

BUGS

628       The ntpd utility has gotten rather fat.  While not huge, it has  gotten
629       larger than might be desirable for an elevated-priority ntpd running on
630       a workstation, particularly since many of the fancy features which con‐
631       sume  the  space  were designed more with a busy primary server, rather
632       than a high stratum workstation in mind.
633
634       Please send bug reports to: http://bugs.ntp.org, bugs@ntp.org
635

NOTES

637       Portions of this document came from FreeBSD.
638
639       This manual page was AutoGen-erated from the ntpd option definitions.
640
641
642
6434.2.8p15                          23 Jun 2020                          ntpd(8)
Impressum