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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | WARNINGS | SEE ALSO | REFERENCES | AUTHOR | SECURITY | AVAILABILITY | COLOPHON |
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CLOCKDIFF(8) iputils CLOCKDIFF(8)
clockdiff - measure clock difference between hosts
clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {destination}
clockdiff Measures clock difference between us and destination
with 1 msec resolution using ICMP TIMESTAMP [2] packets or,
optionally, IP TIMESTAMP option [3] added to ICMP ECHO. [1]
-o
Use IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP
messages. It is useful with some destinations, which do not
support ICMP TIMESTAMP (f.e. Solaris <2.4).
-o1
Slightly different form of -o, namely it uses three-term IP
TIMESTAMP with prespecified hop addresses instead of four
term one. What flavor works better depends on target host.
Particularly, -o is better for Linux.
-T, --time-format ctime iso
Print time stamp in output either ISO-8601 format or
classical ctime format. The ctime format is default. The ISO
time stamp includes timezone, and is easier to parse.
-I
Alias of --time-format iso option and argument.
-h, --help
Print help and exit.
-V, --version
Print version and exit.
• Some nodes (Cisco) use non-standard timestamps, which is
allowed by RFC, but makes timestamps mostly useless.
• Some nodes generate messed timestamps (Solaris>2.4), when
run xntpd. Seems, its IP stack uses a corrupted clock source,
which is synchronized to time-of-day clock periodically and
jumps randomly making timestamps mostly useless. Good news is
that you can use NTP in this case, which is even better.
• clockdiff shows difference in time modulo 24 days.
ping(8), arping(8), tracepath(8).
[1] ICMP ECHO, RFC0792, page 14.
[2] ICMP TIMESTAMP, RFC0792, page 16.
[3] IP TIMESTAMP option, RFC0791, 3.1, page 16.
clockdiff was compiled by Alexey Kuznetsov
<kuznet@ms2.inr.ac.ru>. It was based on code borrowed from BSD
timed daemon.
clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to
be executed. It is safe to be used as set-uid root.
clockdiff is part of iputils package.
This page is part of the iputils (IP utilities) project.
Information about the project can be found at
⟨http://www.skbuff.net/iputils/⟩. If you have a bug report for
this manual page, send it to yoshfuji@skbuff.net,
netdev@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨https://github.com/iputils/iputils.git⟩ on 2023-12-22. (At that
time, the date of the most recent commit that was found in the
repository was 2023-12-22.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
iputils 20221126 CLOCKDIFF(8)
Pages that refer to this page: arping(8)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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