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.Dd November 17, 2023 29.Dt TUNEFS 8 30.Os 31.Sh NAME 32.Nm tunefs 33.Nd tune up an existing UFS file system 34.Sh SYNOPSIS 35.Nm 36.Op Fl A 37.Op Fl a Cm enable | disable 38.Op Fl e Ar maxbpg 39.Op Fl f Ar avgfilesize 40.Op Fl j Cm enable | disable 41.Op Fl J Cm enable | disable 42.Op Fl k Ar held-for-metadata-blocks 43.Op Fl L Ar volname 44.Op Fl l Cm enable | disable 45.Op Fl m Ar minfree 46.Op Fl N Cm enable | disable 47.Op Fl n Cm enable | disable 48.Op Fl o Cm space | time 49.Op Fl p 50.Op Fl s Ar avgfpdir 51.Op Fl S Ar size 52.Op Fl t Cm enable | disable 53.Ar special | filesystem 54.Sh DESCRIPTION 55The 56.Nm 57utility is designed to change the dynamic parameters of a UFS file system 58which affect the layout policies. 59The 60.Nm 61utility cannot be run on an active file system. 62To change an active file system, 63it must be downgraded to read-only or unmounted. 64.Pp 65The parameters which are to be changed are indicated by the flags 66given below: 67.Bl -tag -width indent 68.It Fl A 69The file system has several backups of the super-block. 70Specifying 71this option will cause all backups to be modified as well as the 72primary super-block. 73This is potentially dangerous - use with caution. 74.It Fl a Cm enable | disable 75Turn on/off the administrative POSIX.1e ACL enable flag. 76.It Fl e Ar maxbpg 77Indicate the maximum number of blocks any single file can 78allocate out of a cylinder group before it is forced to begin 79allocating blocks from another cylinder group. 80Typically this value is set to about one quarter of the total blocks 81in a cylinder group. 82The intent is to prevent any single file from using up all the 83blocks in a single cylinder group, 84thus degrading access times for all files subsequently allocated 85in that cylinder group. 86The effect of this limit is to cause big files to do long seeks 87more frequently than if they were allowed to allocate all the blocks 88in a cylinder group before seeking elsewhere. 89For file systems with exclusively large files, 90this parameter should be set higher. 91.It Fl f Ar avgfilesize 92Specify the expected average file size. 93.It Fl j Cm enable | disable 94Turn on/off soft updates journaling. 95.Pp 96Enabling journaling reduces the time spent by 97.Xr fsck_ffs 8 98cleaning up a filesystem after a crash to a few seconds from minutes to hours. 99Without journaling, the time to recover after a crash is a function 100of the number of files in the filesystem and the size of the filesystem. 101With journaling, the time to recover after a crash is a function of the 102amount of activity in the filesystem in the minute before the crash. 103Journaled recovery time is usually only a few seconds and never 104exceeds a minute. 105.Pp 106The drawback to using journaling is that the writes to its log adds 107an extra write load to the media containing the filesystem. 108Thus a write-intensive workload will have reduced throughput on a 109filesystem running with journaling. 110.Pp 111Like all journaling filesystems, the journal recovery will only fix 112issues known to the journal. 113Specifically if a media error occurs, 114the journal will not know about it and hence will not fix it. 115Thus when using journaling, it is still necessary to run a full fsck 116every few months or after a filesystem panic to check for and fix 117any errors brought on by media failure. 118A full fsck can be done by running a background fsck on a live 119filesystem or by running with the 120.Fl f 121flag on an unmounted filesystem. 122When running 123.Xr fsck_ffs 8 124in background on a live filesystem the filesystem performance 125will be about half of normal during the time that the background 126.Xr fsck_ffs 8 127is running. 128Running a full fsck on a UFS filesystem is the equivalent of 129running a scrub on a ZFS filesystem. 130.It Fl J Cm enable | disable 131Turn on/off gjournal flag. 132.It Fl k Ar held-for-metadata-blocks 133Set the amount of space to be held for metadata blocks. 134When set, the file system preference routines will try to save 135the specified amount of space immediately following the inode blocks 136in each cylinder group for use by metadata blocks. 137Clustering the metadata blocks speeds up random file access 138and decreases the running time of 139.Xr fsck 8 . 140While this option can be set at any time, 141it is most effective if set before any data is loaded into the file system. 142By default 143.Xr newfs 8 144sets it to half of the space reserved to minfree. 145.It Fl L Ar volname 146Add/modify an optional file system volume label. 147Legal characters are alphanumerics, dashes, and underscores. 148.It Fl l Cm enable | disable 149Turn on/off MAC multilabel flag. 150.It Fl m Ar minfree 151Specify the percentage of space held back 152from normal users; the minimum free space threshold. 153The default value used is 8%. 154Note that lowering the threshold can adversely affect performance: 155.Bl -bullet 156.It 157Settings of 5% and less force space optimization to 158always be used which will greatly increase the overhead for file 159writes. 160.It 161The file system's ability to avoid fragmentation will be reduced 162when the total free space, including the reserve, drops below 15%. 163As free space approaches zero, throughput can degrade by up to a 164factor of three over the performance obtained at a 10% threshold. 165.El 166.Pp 167If the value is raised above the current usage level, 168users will be unable to allocate files until enough files have 169been deleted to get under the higher threshold. 170.It Fl N Cm enable | disable 171Turn on/off the administrative NFSv4 ACL enable flag. 172.It Fl n Cm enable | disable 173Turn on/off soft updates. 174.It Fl o Cm space | time 175The file system can either try to minimize the time spent 176allocating blocks, or it can attempt to minimize the space 177fragmentation on the disk. 178Optimization for space has much 179higher overhead for file writes. 180The kernel normally changes the preference automatically as 181the percent fragmentation changes on the file system. 182.It Fl p 183Show a summary of what the current tunable settings 184are on the selected file system. 185More detailed information can be 186obtained from the 187.Xr dumpfs 8 188utility. 189.It Fl s Ar avgfpdir 190Specify the expected number of files per directory. 191.It Fl S Ar size 192Specify the softdep journal size in bytes. 193The minimum is 4M. 194.It Fl t Cm enable | disable 195Turn on/off the TRIM enable flag. 196If enabled, and if the underlying device supports the BIO_DELETE 197command, the file system will send a delete request to the underlying 198device for each freed block. 199The trim enable flag is typically set when the underlying device 200uses flash-memory as the device can use the delete command to 201pre-zero or at least avoid copying blocks that have been deleted. 202.Pp 203Note that this does not trim blocks that are already free. 204See the 205.Xr fsck_ffs 8 206.Fl E 207flag. 208.El 209.Pp 210At least one of these flags is required. 211.Sh FILES 212.Bl -tag -width ".Pa /etc/fstab" 213.It Pa /etc/fstab 214read this to determine the device file for a 215specified mount point. 216.El 217.Sh SEE ALSO 218.Xr fs 5 , 219.Xr ffs 7 , 220.Xr tuning 7 , 221.Xr dumpfs 8 , 222.Xr gjournal 8 , 223.Xr growfs 8 , 224.Xr newfs 8 225.Rs 226.%A M. McKusick 227.%A W. Joy 228.%A S. Leffler 229.%A R. Fabry 230.%T "A Fast File System for UNIX" 231.%J "ACM Transactions on Computer Systems 2" 232.%N 3 233.%P pp 181-197 234.%D August 1984 235.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 236.Re 237.Sh HISTORY 238The 239.Nm 240utility appeared in 241.Bx 4.2 . 242.Sh BUGS 243This utility does not work on active file systems. 244To change the root file system, the system must be rebooted 245after the file system is tuned. 246.\" Take this out and a Unix Daemon will dog your steps from now until 247.\" the time_t's wrap around. 248.Pp 249You can tune a file system, but you cannot tune a fish. 250