clockdiff(8) — Linux manual page

CLOCKDIFF(8)                     iputils                    CLOCKDIFF(8)

NAME

       clockdiff - measure clock difference between hosts

SYNOPSIS

       clockdiff [-o] [-o1] [--time-format ctime iso] [-V] {destination}

DESCRIPTION

       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]

OPTIONS

       -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.

WARNINGS

           • 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.

SEE ALSO

       ping(8), arping(8), tracepath(8).

REFERENCES

       [1] ICMP ECHO, RFC0792, page 14.

       [2] ICMP TIMESTAMP, RFC0792, page 16.

       [3] IP TIMESTAMP option, RFC0791, 3.1, page 16.

AUTHOR

       clockdiff was compiled by Alexey Kuznetsov
       <kuznet@ms2.inr.ac.ru>. It was based on code borrowed from BSD
       timed daemon.

SECURITY

       clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to
       be executed. It is safe to be used as set-uid root.

AVAILABILITY

       clockdiff is part of iputils package.

COLOPHON

       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 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-10.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
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       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

iputils 20240117                                            CLOCKDIFF(8)

Pages that refer to this page: arping(8)

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