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.\" $FreeBSD$ 30.\" 31.Dd January 29, 2019 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 k Ar held-for-metadata-blocks 46.Op Fl L Ar volname 47.Op Fl l Cm enable | disable 48.Op Fl m Ar minfree 49.Op Fl N Cm enable | disable 50.Op Fl n Cm enable | disable 51.Op Fl o Cm space | time 52.Op Fl p 53.Op Fl s Ar avgfpdir 54.Op Fl S Ar size 55.Op Fl t Cm enable | disable 56.Ar special | filesystem 57.Sh DESCRIPTION 58The 59.Nm 60utility is designed to change the dynamic parameters of a UFS file system 61which affect the layout policies. 62The 63.Nm 64utility cannot be run on an active file system. 65To change an active file system, 66it must be downgraded to read-only or unmounted. 67.Pp 68The parameters which are to be changed are indicated by the flags 69given below: 70.Bl -tag -width indent 71.It Fl A 72The file system has several backups of the super-block. 73Specifying 74this option will cause all backups to be modified as well as the 75primary super-block. 76This is potentially dangerous - use with caution. 77.It Fl a Cm enable | disable 78Turn on/off the administrative POSIX.1e ACL enable flag. 79.It Fl e Ar maxbpg 80Indicate the maximum number of blocks any single file can 81allocate out of a cylinder group before it is forced to begin 82allocating blocks from another cylinder group. 83Typically this value is set to about one quarter of the total blocks 84in a cylinder group. 85The intent is to prevent any single file from using up all the 86blocks in a single cylinder group, 87thus degrading access times for all files subsequently allocated 88in that cylinder group. 89The effect of this limit is to cause big files to do long seeks 90more frequently than if they were allowed to allocate all the blocks 91in a cylinder group before seeking elsewhere. 92For file systems with exclusively large files, 93this parameter should be set higher. 94.It Fl f Ar avgfilesize 95Specify the expected average file size. 96.It Fl j Cm enable | disable 97Turn on/off soft updates journaling. 98.It Fl J Cm enable | disable 99Turn on/off gjournal flag. 100.It Fl k Ar held-for-metadata-blocks 101Set the amount of space to be held for metadata blocks. 102When set, the file system preference routines will try to save 103the specified amount of space immediately following the inode blocks 104in each cylinder group for use by metadata blocks. 105Clustering the metadata blocks speeds up random file access 106and decreases the running time of 107.Xr fsck 8 . 108While this option can be set at any time, 109it is most effective if set before any data is loaded into the file system. 110By default 111.Xr newfs 8 112sets it to half of the space reserved to minfree. 113.It Fl L Ar volname 114Add/modify an optional file system volume label. 115Legal characters are alphanumerics, dashes, and underscores. 116.It Fl l Cm enable | disable 117Turn on/off MAC multilabel flag. 118.It Fl m Ar minfree 119Specify the percentage of space held back 120from normal users; the minimum free space threshold. 121The default value used is 8%. 122Note that lowering the threshold can adversely affect performance: 123.Bl -bullet 124.It 125Settings of 5% and less force space optimization to 126always be used which will greatly increase the overhead for file 127writes. 128.It 129The file system's ability to avoid fragmentation will be reduced 130when the total free space, including the reserve, drops below 15%. 131As free space approaches zero, throughput can degrade by up to a 132factor of three over the performance obtained at a 10% threshold. 133.El 134.Pp 135If the value is raised above the current usage level, 136users will be unable to allocate files until enough files have 137been deleted to get under the higher threshold. 138.It Fl N Cm enable | disable 139Turn on/off the administrative NFSv4 ACL enable flag. 140.It Fl n Cm enable | disable 141Turn on/off soft updates. 142.It Fl o Cm space | time 143The file system can either try to minimize the time spent 144allocating blocks, or it can attempt to minimize the space 145fragmentation on the disk. 146Optimization for space has much 147higher overhead for file writes. 148The kernel normally changes the preference automatically as 149the percent fragmentation changes on the file system. 150.It Fl p 151Show a summary of what the current tunable settings 152are on the selected file system. 153More detailed information can be 154obtained from the 155.Xr dumpfs 8 156utility. 157.It Fl s Ar avgfpdir 158Specify the expected number of files per directory. 159.It Fl S Ar size 160Specify the softdep journal size in bytes. 161The minimum is 4M. 162.It Fl t Cm enable | disable 163Turn on/off the TRIM enable flag. 164If enabled, and if the underlying device supports the BIO_DELETE 165command, the file system will send a delete request to the underlying 166device for each freed block. 167The trim enable flag is typically set when the underlying device 168uses flash-memory as the device can use the delete command to 169pre-zero or at least avoid copying blocks that have been deleted. 170.Pp 171Note that this does not trim blocks that are already free. 172See the 173.Xr fsck_ffs 8 174.Fl E 175flag. 176.El 177.Pp 178At least one of these flags is required. 179.Sh FILES 180.Bl -tag -width ".Pa /etc/fstab" 181.It Pa /etc/fstab 182read this to determine the device file for a 183specified mount point. 184.El 185.Sh SEE ALSO 186.Xr fs 5 , 187.Xr dumpfs 8 , 188.Xr gjournal 8 , 189.Xr growfs 8 , 190.Xr newfs 8 191.Rs 192.%A M. McKusick 193.%A W. Joy 194.%A S. Leffler 195.%A R. Fabry 196.%T "A Fast File System for UNIX" 197.%J "ACM Transactions on Computer Systems 2" 198.%N 3 199.%P pp 181-197 200.%D August 1984 201.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 202.Re 203.Sh HISTORY 204The 205.Nm 206utility appeared in 207.Bx 4.2 . 208.Sh BUGS 209This utility does not work on active file systems. 210To change the root file system, the system must be rebooted 211after the file system is tuned. 212.\" Take this out and a Unix Daemon will dog your steps from now until 213.\" the time_t's wrap around. 214.Pp 215You can tune a file system, but you cannot tune a fish. 216