1.\" $OpenBSD: sync.8,v 1.11 2007/05/31 19:19:15 jmc Exp $ 2.\" $NetBSD: sync.8,v 1.6 1995/03/21 09:11:35 cgd Exp $ 3.\" 4.\" Copyright (c) 1980, 1991, 1993 5.\" The Regents of the University of California. All rights reserved. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)sync.8 8.1 (Berkeley) 5/31/93 32.\" 33.Dd $Mdocdate: May 31 2007 $ 34.Dt SYNC 8 35.Os 36.Sh NAME 37.Nm sync 38.Nd force completion of pending disk writes (flush cache) 39.Sh SYNOPSIS 40.Nm sync 41.Sh DESCRIPTION 42The 43.Nm 44utility can be called to ensure that all disk writes have been completed before 45the processor is halted in a way not suitably done by 46.Xr reboot 8 47or 48.Xr halt 8 . 49Generally, it is preferable to use 50.Xr reboot 8 51or 52.Xr halt 8 53to shut down the system, 54as they may perform additional actions 55such as resynchronizing the hardware clock 56and flushing internal caches before performing a final 57.Nm sync . 58.Pp 59.Nm 60utilizes the 61.Xr sync 2 62function call. 63.Sh SEE ALSO 64.Xr fsync 2 , 65.Xr sync 2 , 66.Xr halt 8 , 67.Xr reboot 8 , 68.Xr update 8 69.Sh HISTORY 70A 71.Nm 72command appeared in 73.At v6 . 74