sync(8)

sync8

Force completion of pending disk writes (flush cache)

Usage

sync

Overview

The sync utility can be called to ensure that all disk writes have been completed before the processor is halted in a way not suitably done by reboot(8) or halt(8). Generally, it is preferable to use reboot(8) or halt(8) to shut down the system, as they may perform additional actions such as resynchronizing the hardware clock and flushing internal caches before performing a final sync.

sync utilizes the sync(2) function.

Releases

61 releases since OpenBSD 2.1; the text changed 9 times.

  1. 2.1
  2. 2.2–2.3
  3. 2.4
  4. 2.5
  5. 2.6–3.3
  6. 3.4–4.1
  7. 4.2–4.9
  8. 5.0–5.8
  9. 5.9–6.0
  10. 6.1–8.0

History

A sync command appeared in Version 4 AT&T UNIX.

From man 8.0-current-20261101 in OpenBSD 8.0-current (2026-11-01). Parsed by carta from the page's mdoc source.