1NTPFROB(8)                          NTPsec                          NTPFROB(8)
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NAME

6       ntpfrob - frob the clock hardware
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SYNOPSIS

9       ntpfrob [-A] [-b bump] [-a tick] [-p ppsdev] [-c] [-e] [-r] [-?] [-h]
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DESCRIPTION

12       The ntpfrob program frobs the local clock hardware. It collects several
13       small diagnostic functions into a set that will differ depending on
14       your platform and underlying system calls. Portions of it formerly
15       traveled as tickadj and some undocumented small utilities.
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COMMAND LINE OPTIONS

18       -a tick
19           Set the kernel variable tick to the value tick specifies.
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21       -A
22           Display the kernel variable tick.
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24       -b bump
25           Bump the clock by a specified number of microseconds.
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27       -c
28           Compute and display clock jitter.
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30       -d
31           display values extracted via adjtimex(2).
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33       -D
34           display values extracted via adjtimex(2) forcibly including PPS.
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36       -e
37           Measure clock precision.
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39       -j
40           Generate a report in self-describing JSON.
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42       -p ppsdev
43           Look for PPS pulses on a specified device
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45       -r
46           Raw mode. Only applies to the jitter mode, and means the raw clock
47           samples should be emitted to stdout for post analysis.
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49       -?
50           Print usage and exit.
51
52       -h
53           Print usage and exit.
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55       -V
56           Print the version string and exit.
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USAGE

59       Documentation for some of these functions is scanty; this is a problem
60       inherited from ancient days along with their code. If you suspect you
61       may need to use them, reading the source code may be wise. If you
62       believe you understand the code in more detail than any of these
63       descriptions, please explain it to the NTPsec maintainers.
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65       Normally this tool reports in an eyeball-friendly unstructured text
66       format. With the -j option (where applicable) it reports JSON records.
67       Note that the -j option should be given before any mode option.
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69       The reporting formats of this tool should be considered unstable; they
70       may change as diagnostics are added or improved. JSON reports will be
71       kept forward-compatible through changes.
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73   Clock tick adjustment
74       The -A function reads your clock’s tick rate in microseconds. The -a
75       function sets it. Both rely on the adjtimex(2) system call. This mode
76       finishes by reporting the tick value and (if available) the tick
77       adjustment value.
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79       The -j option applies to this mode.
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81       Tweaking your tick rate is almost never necessary on hardware new
82       enough to have a fully POSIX.1-2001-conformant Unix.
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84   Clock bump
85       Sometimes it is diagnostically interesting to perturb your clock to
86       watch how ntpd responds and makes corrections. This option does that.
87
88   Clock jitter measurement
89       The -c option can be used to determine the timing jitter due to the
90       operating system in a gettimeofday() call. For most systems, the
91       dominant contribution to the jitter budget is the period of the
92       hardware interrupt, usually in the range between 10 us and 1 ms. For
93       those systems with microsecond counters, the jitter is dominated only
94       by the operating system.
95
96       The -j option applies to this mode. With the -r option, write the raw,
97       unsorted clock samples to standard output for post-analysis. All but
98       the last -j or -r option before the -c mode flag is ignored.
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100   Pulse-per-second check
101       The -p option shows whether the  PPS-API (RFC 2783 kernel PPS
102       interface) finds PPS on a specified device.
103
104   Measure clock precision
105       The -e option measure the resolution of the system clock, watching how
106       the current time changes as we read it repeatedly.
107
108       The -j option applies to this mode.
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EXIT STATUS

111       One of the following exit values will be returned:
112
113       0 (EXIT_SUCCESS)
114           Successful program execution.
115
116       1 (EXIT_FAILURE)
117           The operation failed or the command invocation was not valid.
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121NTPsec                            2023-08-03                        NTPFROB(8)
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