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 June 22, 2011 32.Dt TUNEFS 8 33.Os 34.Sh NAME 35.Nm tunefs 36.Nd tune up an existing UFS 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.Op Fl t Cm enable | disable 55.Ar special | filesystem 56.Sh DESCRIPTION 57The 58.Nm 59utility is designed to change the dynamic parameters of a UFS file system 60which affect the layout policies. 61The 62.Nm 63utility cannot be run on an active file system. 64To change an active file system, 65it must be downgraded to read-only or unmounted. 66.Pp 67The parameters which are to be changed are indicated by the flags 68given below: 69.Bl -tag -width indent 70.It Fl A 71The file system has several backups of the super-block. 72Specifying 73this option will cause all backups to be modified as well as the 74primary super-block. 75This is potentially dangerous - use with caution. 76.It Fl a Cm enable | disable 77Turn on/off the administrative POSIX.1e ACL enable flag. 78.It Fl e Ar maxbpg 79Indicate the maximum number of blocks any single file can 80allocate out of a cylinder group before it is forced to begin 81allocating blocks from another cylinder group. 82Typically this value is set to about one quarter of the total blocks 83in a cylinder group. 84The intent is to prevent any single file from using up all the 85blocks in a single cylinder group, 86thus degrading access times for all files subsequently allocated 87in that cylinder group. 88The effect of this limit is to cause big files to do long seeks 89more frequently than if they were allowed to allocate all the blocks 90in a cylinder group before seeking elsewhere. 91For file systems with exclusively large files, 92this parameter should be set higher. 93.It Fl f Ar avgfilesize 94Specify the expected average file size. 95.It Fl j Cm enable | disable 96Turn on/off soft updates journaling. 97.It Fl J Cm enable | disable 98Turn on/off gjournal flag. 99.It Fl L Ar volname 100Add/modify an optional file system volume label. 101.It Fl l Cm enable | disable 102Turn on/off MAC multilabel flag. 103.It Fl m Ar minfree 104Specify the percentage of space held back 105from normal users; the minimum free space threshold. 106The default value used is 8%. 107Note that lowering the threshold can adversely affect performance: 108.Bl -bullet 109.It 110Settings of 5% and less force space optimization to 111always be used which will greatly increase the overhead for file 112writes. 113.It 114The file system's ability to avoid fragmentation will be reduced 115when the total free space, including the reserve, drops below 15%. 116As free space approaches zero, throughput can degrade by up to a 117factor of three over the performance obtained at a 10% threshold. 118.El 119.Pp 120If the value is raised above the current usage level, 121users will be unable to allocate files until enough files have 122been deleted to get under the higher threshold. 123.It Fl N Cm enable | disable 124Turn on/off the administrative NFSv4 ACL enable flag. 125.It Fl n Cm enable | disable 126Turn on/off soft updates. 127.It Fl o Cm space | time 128The file system can either try to minimize the time spent 129allocating blocks, or it can attempt to minimize the space 130fragmentation on the disk. 131Optimization for space has much 132higher overhead for file writes. 133The kernel normally changes the preference automatically as 134the percent fragmentation changes on the file system. 135.It Fl p 136Show a summary of what the current tunable settings 137are on the selected file system. 138More detailed information can be 139obtained from the 140.Xr dumpfs 8 141utility. 142.It Fl s Ar avgfpdir 143Specify the expected number of files per directory. 144.It Fl S Ar size 145Specify the softdep journal size in bytes. 146The minimum is 4M. 147.It Fl t Cm enable | disable 148Turn on/off the TRIM enable flag. 149If enabled, and if the underlying device supports the BIO_DELETE 150command, the file system will send a delete request to the underlying 151device for each freed block. 152The trim enable flag is typically set when the underlying device 153uses flash-memory as the device can use the delete command to 154pre-zero or at least avoid copying blocks that have been deleted. 155.El 156.Pp 157At least one of the above flags is required. 158.Sh FILES 159.Bl -tag -width ".Pa /etc/fstab" 160.It Pa /etc/fstab 161read this to determine the device file for a 162specified mount point. 163.El 164.Sh SEE ALSO 165.Xr fs 5 , 166.Xr dumpfs 8 , 167.Xr gjournal 8 , 168.Xr growfs 8 , 169.Xr newfs 8 170.Rs 171.%A M. McKusick 172.%A W. Joy 173.%A S. Leffler 174.%A R. Fabry 175.%T "A Fast File System for UNIX" 176.%J "ACM Transactions on Computer Systems 2" 177.%N 3 178.%P pp 181-197 179.%D August 1984 180.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 181.Re 182.Sh HISTORY 183The 184.Nm 185utility appeared in 186.Bx 4.2 . 187.Sh BUGS 188This utility does not work on active file systems. 189To change the root file system, the system must be rebooted 190after the file system is tuned. 191.\" Take this out and a Unix Daemon will dog your steps from now until 192.\" the time_t's wrap around. 193.Pp 194You can tune a file system, but you cannot tune a fish. 195