1.\" $NetBSD: sync.8,v 1.16 2016/08/12 02:59:23 sevan Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)sync.8 8.1 (Berkeley) 5/31/93 31.\" 32.Dd August 12, 2016 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 43program can be called to ensure that all disk writes have been 44completed before the processor is halted in a way not suitably done by 45.Xr reboot 8 46or 47.Xr halt 8 . 48Generally, it is preferable to use 49.Xr reboot 8 50or 51.Xr halt 8 52to shut down the system, 53as they may perform additional actions 54such as resynchronizing the hardware clock 55and flushing internal caches before performing a final 56.Nm . 57.Pp 58The 59.Nm 60program simply invokes the 61.Xr sync 2 62system call. 63.Sh SEE ALSO 64.Xr fsync 2 , 65.Xr sync 2 , 66.Xr halt 8 , 67.Xr reboot 8 68.Sh HISTORY 69A 70.Nm 71command appeared in 72.At v4 . 73