Provided by: iputils-clockdiff_20240117-1build1_amd64 
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.