1NTPFROB(8) NTPsec NTPFROB(8)
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6 ntpfrob - frob the clock hardware
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9 ntpfrob [-A] [-b bump] [-a tick] [-p ppsdev] [-c] [-e] [-r] [-?] [-h]
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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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18 -a tick
19 Set the kernel variable tick to the value tick specifies.
20 -A
22 Display the kernel variable tick.
23 -b bump
25 Bump the clock by a specified number of microseconds.
26 -c
28 Compute and display clock jitter.
29 -d
31 display values extracted via adjtimex(2).
32 -D
34 display values extracted via adjtimex(2) forcibly including PPS.
35 -e
37 Measure clock precision.
38 -j
40 Generate a report in self-describing JSON.
41 -p ppsdev
43 Look for PPS pulses on a specified device
44 -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.
48 -?
50 Print usage and exit.
51 -h
53 Print usage and exit.
54 -V
56 Print the version string and exit.
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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.
64 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.
68 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.
72 Clock tick adjustment
74 The -A function reads your clockâs 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.
78 The -j option applies to this mode.
80 Tweaking your tick rate is almost never necessary on hardware new
82 enough to have a fully POSIX.1-2001-conformant Unix.
83 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 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 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.
99 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 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 The -j option applies to this mode.
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111 One of the following exit values will be returned:
112 0 (EXIT_SUCCESS)
114 Successful program execution.
115 1 (EXIT_FAILURE)
117 The operation failed or the command invocation was not valid.
118NTPsec 2023-08-03 NTPFROB(8)