CLOCKDIFF(8)

📦
this version · 6 versions
, in alpine 3.24, arch rolling, fedora 43, fedora 44, nixpkgs unstable, ubuntu resolute, ubuntu stonking

💖 CLOCKDIFF(8) 💖

okay bestie, gather round, we're doing the clockdiff page from iputils and it's lowkey iconic. this is section 8, so it's a sysadmin situation, and it's literally about figuring out how far apart two clocks are. clock girl summer fr fr 🕐✨

✨ NAME ✨

clockdiff — measure clock difference between hosts 🫶

🌸 SYNOPSIS 🌸

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

🦋 DESCRIPTION 🦋

So the whole vibe of clockdiff is: it measures the clock difference between us and destination, with 1 msec resolution. how does it do that? it uses ICMP TIMESTAMP packets [2] or, optionally, the IP TIMESTAMP option [3] added to an ICMP ECHO. [1] it's giving "detective but make it packets". no cap 💅

💜 OPTIONS 💜

  • -o — uses IP TIMESTAMP with ICMP ECHO instead of ICMP TIMESTAMP messages. this one is useful with certain destinations that do NOT support ICMP TIMESTAMP (f.e. Solaris <2.4). some hosts are just built different, and not in a good way 🙈
  • -o1 — slightly different form of -o, namely it uses three-term IP TIMESTAMP with prespecified hop addresses instead of the four-term one. which flavor works better depends on the target host. particularly, -o is better for Linux. ✨
  • -T, --time-format ctime iso — prints the time stamp in the output either in ISO-8601 format or in classic ctime format. the ctime format is the default. the ISO time stamp includes the timezone, and it's easier to parse. periodt 📅
  • -I — alias of the --time-format iso option and argument. cute shortcut energy 🎀
  • -h, --help — prints help and exits. queen behavior 👑
  • -V, --version — prints version and exits. 💫

😭 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. yeah. 24 days. do with that what you will bestie 😌
ngl the Cisco one and the Solaris one are giving "we tried our best and our best was not enough". but hey, NTP ate and left no crumbs.

👑 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 the BSD timed daemon. the way this was literally built on borrowed code and still slayed — respect 🫡

🔥 SECURITY 🔥

clockdiff requires CAP_NET_RAW and CAP_SYS_NICE capabilities to be executed. It is safe to be used as set-uid root. yes bestie, set-uid root and it's SAFE, we love a responsible icon 💖

🌟 AVAILABILITY 🌟

clockdiff is part of the iputils package. 💫

aaaand that's the whole page, you ate that fr fr 💅✨ this is iputils version 20250605, dating all the way back to 20250605, so go forth and measure some clocks, bestie 🕰️🦋💖

📦 where this page comes from