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.\" 4. 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.\" $FreeBSD$ 30.\" 31.Dd March 6, 2010 32.Dt TUNEFS 8 33.Os 34.Sh NAME 35.Nm tunefs 36.Nd tune up an existing file system 37.Sh SYNOPSIS 38.Nm 39.Op Fl A 40.Op Fl a Cm enable | disable 41.Op Fl e Ar maxbpg 42.Op Fl f Ar avgfilesize 43.Op Fl j Cm enable | disable 44.Op Fl J Cm enable | disable 45.Op Fl L Ar volname 46.Op Fl l Cm enable | disable 47.Op Fl m Ar minfree 48.Op Fl N Cm enable | disable 49.Op Fl n Cm enable | disable 50.Op Fl o Cm space | time 51.Op Fl p 52.Op Fl s Ar avgfpdir 53.Op Fl S Ar size 54.Ar special | filesystem 55.Sh DESCRIPTION 56The 57.Nm 58utility is designed to change the dynamic parameters of a file system 59which affect the layout policies. 60The 61.Nm 62utility cannot be run on an active file system. 63To change an active file system, 64it must be downgraded to read-only or unmounted. 65.Pp 66The parameters which are to be changed are indicated by the flags 67given below: 68.Bl -tag -width indent 69.It Fl A 70The file system has several backups of the super-block. 71Specifying 72this option will cause all backups to be modified as well as the 73primary super-block. 74This is potentially dangerous - use with caution. 75.It Fl a Cm enable | disable 76Turn on/off the administrative POSIX.1e ACL enable flag. 77.It Fl e Ar maxbpg 78Indicate the maximum number of blocks any single file can 79allocate out of a cylinder group before it is forced to begin 80allocating blocks from another cylinder group. 81Typically this value is set to about one quarter of the total blocks 82in a cylinder group. 83The intent is to prevent any single file from using up all the 84blocks in a single cylinder group, 85thus degrading access times for all files subsequently allocated 86in that cylinder group. 87The effect of this limit is to cause big files to do long seeks 88more frequently than if they were allowed to allocate all the blocks 89in a cylinder group before seeking elsewhere. 90For file systems with exclusively large files, 91this parameter should be set higher. 92.It Fl f Ar avgfilesize 93Specify the expected average file size. 94.It Fl j Cm enable | disable 95Turn on/off soft updates journaling. 96.It Fl J Cm enable | disable 97Turn on/off gjournal flag. 98.It Fl L Ar volname 99Add/modify an optional file system volume label. 100.It Fl l Cm enable | disable 101Turn on/off MAC multilabel flag. 102.It Fl m Ar minfree 103Specify the percentage of space held back 104from normal users; the minimum free space threshold. 105The default value used is 8%. 106Note that lowering the threshold can adversely affect performance: 107.Bl -bullet 108.It 109Settings of 5% and less force space optimization to 110always be used which will greatly increase the overhead for file 111writes. 112.It 113The file system's ability to avoid fragmentation will be reduced 114when the total free space, including the reserve, drops below 15%. 115As free space approaches zero, throughput can degrade by up to a 116factor of three over the performance obtained at a 10% threshold. 117.El 118.Pp 119If the value is raised above the current usage level, 120users will be unable to allocate files until enough files have 121been deleted to get under the higher threshold. 122.It Fl N Cm enable | disable 123Turn on/off the administrative NFSv4 ACL enable flag. 124.It Fl n Cm enable | disable 125Turn on/off soft updates. 126.It Fl o Cm space | time 127The file system can either try to minimize the time spent 128allocating blocks, or it can attempt to minimize the space 129fragmentation on the disk. 130Optimization for space has much 131higher overhead for file writes. 132The kernel normally changes the preference automatically as 133the percent fragmentation changes on the file system. 134.It Fl p 135Show a summary of what the current tunable settings 136are on the selected file system. 137More detailed information can be 138obtained from the 139.Xr dumpfs 8 140utility. 141.It Fl s Ar avgfpdir 142Specify the expected number of files per directory. 143.It Fl S Ar size 144Specify the softdep journal size in bytes. 145The minimum is 4M. 146.El 147.Pp 148At least one of the above flags is required. 149.Sh FILES 150.Bl -tag -width ".Pa /etc/fstab" 151.It Pa /etc/fstab 152read this to determine the device file for a 153specified mount point. 154.El 155.Sh SEE ALSO 156.Xr fs 5 , 157.Xr dumpfs 8 , 158.Xr gjournal 8 , 159.Xr newfs 8 160.Rs 161.%A M. McKusick 162.%A W. Joy 163.%A S. Leffler 164.%A R. Fabry 165.%T "A Fast File System for UNIX" 166.%J "ACM Transactions on Computer Systems 2" 167.%N 3 168.%P pp 181-197 169.%D August 1984 170.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 171.Re 172.Sh HISTORY 173The 174.Nm 175utility appeared in 176.Bx 4.2 . 177.Sh BUGS 178This utility does not work on active file systems. 179To change the root file system, the system must be rebooted 180after the file system is tuned. 181.\" Take this out and a Unix Daemon will dog your steps from now until 182.\" the time_t's wrap around. 183.Pp 184You can tune a file system, but you cannot tune a fish. 185