1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)tunefs.8 8.2 (Berkeley) 12/11/93 29.\" $FreeBSD: src/sbin/tunefs/tunefs.8,v 1.11.2.6 2003/01/23 11:14:02 maxim Exp $ 30.\" $DragonFly: src/sbin/tunefs/tunefs.8,v 1.3 2006/02/17 19:33:33 swildner Exp $ 31.\" 32.Dd December 11, 1993 33.Dt TUNEFS 8 34.Os 35.Sh NAME 36.Nm tunefs 37.Nd tune up an existing UFS filesystem 38.Sh SYNOPSIS 39.Nm 40.Op Fl \&Ap 41.Op Fl a Ar maxcontig 42.Op Fl d Ar rotdelay 43.Op Fl e Ar maxbpg 44.Op Fl f Ar avgfilesize 45.Op Fl m Ar minfree 46.Bk -words 47.Op Fl n Cm enable | disable 48.Op Fl o Cm space | time 49.Op Fl s Ar avgfpdir 50.Ek 51.Brq Ar special | filesystem 52.Sh DESCRIPTION 53.Nm Tunefs 54is designed to change the dynamic parameters of a filesystem 55which affect the layout policies. 56The parameters which are to be changed are indicated by the flags 57given below: 58.Bl -tag -width indent 59.It Fl A 60The filesystem has several backups of the super-block. 61Specifying 62this option will cause all backups to be modified as well as the 63primary super-block. 64This is potentially dangerous - use with caution. 65.It Fl a Ar maxcontig 66Specify the maximum number of contiguous blocks that will 67be laid out before forcing a rotational delay (see 68.Fl d 69below). 70The default value is one, since most device drivers require 71an interrupt per disk transfer. 72Device drivers that can chain several buffers together in a single 73transfer should set this to the maximum chain length. 74.It Fl d Ar rotdelay 75Specify the expected time (in milliseconds) 76to service a transfer completion 77interrupt and initiate a new transfer on the same disk. 78It is used to decide how much rotational spacing to place between 79successive blocks in a file. 80.It Fl e Ar maxbpg 81Indicate the maximum number of blocks any single file can 82allocate out of a cylinder group before it is forced to begin 83allocating blocks from another cylinder group. 84Typically this value is set to about one quarter of the total blocks 85in a cylinder group. 86The intent is to prevent any single file from using up all the 87blocks in a single cylinder group, 88thus degrading access times for all files subsequently allocated 89in that cylinder group. 90The effect of this limit is to cause big files to do long seeks 91more frequently than if they were allowed to allocate all the blocks 92in a cylinder group before seeking elsewhere. 93For filesystems with exclusively large files, 94this parameter should be set higher. 95.It Fl f Ar avgfilezsize 96Specify the expected average file size. 97.It Fl m Ar minfree 98Specify the percentage of space held back 99from normal users; the minimum free space threshold. 100The default value used is 8%. 101This value can be set to zero, however up to a factor of three 102in throughput will be lost over the performance obtained at a 10% 103threshold. 104Settings of 5% and less force space optimization to 105always be used which will greatly increase the overhead for file 106writes. 107Note that if the value is raised above the current usage level, 108users will be unable to allocate files until enough files have 109been deleted to get under the higher threshold. 110.It Fl n Cm enable | disable 111Turn on/off soft updates. 112.It Fl o Cm space | time 113The filesystem can either try to minimize the time spent 114allocating blocks, or it can attempt to minimize the space 115fragmentation on the disk. 116Optimization for space has much 117higher overhead for file writes. 118The kernel normally changes the preference automatically as 119the percent fragmentation changes on the filesystem. 120.It Fl p 121Show a summary of what the current tunable settings 122are on the selected filesystem. 123More detailed information can be 124obtained in the 125.Xr dumpfs 8 126manual page. 127.It Fl s Ar avgfpdir 128Specify the expected number of files per directory. 129.El 130.Sh FILES 131.Bl -tag -width /etc/fstab -compact 132.It Pa /etc/fstab 133read this to determine the device file for a 134specified mount point. 135.El 136.Sh SEE ALSO 137.Xr fs 5 , 138.Xr UFS 5 , 139.Xr dumpfs 8 , 140.Xr newfs 8 141.Rs 142.%A M. McKusick 143.%A W. Joy 144.%A S. Leffler 145.%A R. Fabry 146.%T "A Fast File System for UNIX" 147.%J "ACM Transactions on Computer Systems 2" 148.%N 3 149.%P pp 181-197 150.%D August 1984 151.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 152.Re 153.Sh HISTORY 154The 155.Nm 156command appeared in 157.Bx 4.2 . 158.Sh BUGS 159This program should work on mounted and active filesystems. 160Because the super-block is not kept in the buffer cache, 161the changes will only take effect if the program 162is run on dismounted filesystems. 163To change the root filesystem, the system must be rebooted 164after the filesystem is tuned. 165.\" Take this out and a Unix Demon will dog your steps from now until 166.\" the time_t's wrap around. 167.Pp 168You can tune a filesystem, but you can't tune a fish. 169