1.\"- 2.\" Copyright (c) 1980, 1991, 1993 3.\" The Regents of the University of California. All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. Neither the name of the University nor the names of its contributors 14.\" may be used to endorse or promote products derived from this software 15.\" without specific prior written permission. 16.\" 17.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27.\" SUCH DAMAGE. 28.\" 29.\" @(#)sync.8 8.1 (Berkeley) 5/31/93 30.\" $FreeBSD$ 31.\" 32.Dd May 31, 1993 33.Dt SYNC 8 34.Os 35.Sh NAME 36.Nm sync 37.Nd force completion of pending disk writes (flush cache) 38.Sh SYNOPSIS 39.Nm 40.Sh DESCRIPTION 41The 42.Nm 43utility 44can be called to ensure that all disk writes have been completed before the 45processor 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 . 58.Pp 59The 60.Nm 61utility utilizes the 62.Xr sync 2 63function call. 64.Sh SEE ALSO 65.Xr fsync 2 , 66.Xr sync 2 , 67.Xr syncer 4 , 68.Xr halt 8 , 69.Xr reboot 8 70.Sh HISTORY 71A 72.Nm 73utility appeared in 74.At v4 . 75