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 August 16, 2022 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.Pp 99Enabling journaling reduces the time spent by 100.Xr fsck_ffs 8 101cleaning up a filesystem after a crash to a few seconds from minutes to hours. 102Without journaling, the time to recover after a crash is a function 103of the number of files in the filesystem and the size of the filesystem. 104With journaling, the time to recover after a crash is a function of the 105amount of activity in the filesystem in the minute before the crash. 106Journaled recovery time is usually only a few seconds and never 107exceeds a minute. 108.Pp 109The drawback to using journaling is that the writes to its log adds 110an extra write load to the media containing the filesystem. 111Thus a write-intensive workload will have reduced throughput on a 112filesystem running with journaling. 113.Pp 114Like all journaling filesystems, the journal recovery will only fix 115issues known to the journal. 116Specifically if a media error occurs, 117the journal will not know about it and hence will not fix it. 118Thus when using journaling, it is still necessary to run a full fsck 119every few months or after a filesystem panic to check for and fix 120any errors brought on by media failure. 121A full fsck can be done by running a background fsck on a live 122filesystem or by running with the 123.Fl f 124flag on an unmounted filesystem. 125When running 126.Xr fsck_ffs 8 127in background on a live filesystem the filesystem performance 128will be about half of normal during the time that the background 129.Xr fsck_ffs 8 130is running. 131Running a full fsck on a UFS filesystem is the equivalent of 132running a scrub on a ZFS filesystem. 133.Pp 134Presently it is not possible to take a snapshot on a UFS filesystem 135running with journaled soft updates. 136Thus it is not possible to reliably dump mounted filesystems or 137to run background fsck on filesystems enabled for journaling. 138.It Fl J Cm enable | disable 139Turn on/off gjournal flag. 140.It Fl k Ar held-for-metadata-blocks 141Set the amount of space to be held for metadata blocks. 142When set, the file system preference routines will try to save 143the specified amount of space immediately following the inode blocks 144in each cylinder group for use by metadata blocks. 145Clustering the metadata blocks speeds up random file access 146and decreases the running time of 147.Xr fsck 8 . 148While this option can be set at any time, 149it is most effective if set before any data is loaded into the file system. 150By default 151.Xr newfs 8 152sets it to half of the space reserved to minfree. 153.It Fl L Ar volname 154Add/modify an optional file system volume label. 155Legal characters are alphanumerics, dashes, and underscores. 156.It Fl l Cm enable | disable 157Turn on/off MAC multilabel flag. 158.It Fl m Ar minfree 159Specify the percentage of space held back 160from normal users; the minimum free space threshold. 161The default value used is 8%. 162Note that lowering the threshold can adversely affect performance: 163.Bl -bullet 164.It 165Settings of 5% and less force space optimization to 166always be used which will greatly increase the overhead for file 167writes. 168.It 169The file system's ability to avoid fragmentation will be reduced 170when the total free space, including the reserve, drops below 15%. 171As free space approaches zero, throughput can degrade by up to a 172factor of three over the performance obtained at a 10% threshold. 173.El 174.Pp 175If the value is raised above the current usage level, 176users will be unable to allocate files until enough files have 177been deleted to get under the higher threshold. 178.It Fl N Cm enable | disable 179Turn on/off the administrative NFSv4 ACL enable flag. 180.It Fl n Cm enable | disable 181Turn on/off soft updates. 182.It Fl o Cm space | time 183The file system can either try to minimize the time spent 184allocating blocks, or it can attempt to minimize the space 185fragmentation on the disk. 186Optimization for space has much 187higher overhead for file writes. 188The kernel normally changes the preference automatically as 189the percent fragmentation changes on the file system. 190.It Fl p 191Show a summary of what the current tunable settings 192are on the selected file system. 193More detailed information can be 194obtained from the 195.Xr dumpfs 8 196utility. 197.It Fl s Ar avgfpdir 198Specify the expected number of files per directory. 199.It Fl S Ar size 200Specify the softdep journal size in bytes. 201The minimum is 4M. 202.It Fl t Cm enable | disable 203Turn on/off the TRIM enable flag. 204If enabled, and if the underlying device supports the BIO_DELETE 205command, the file system will send a delete request to the underlying 206device for each freed block. 207The trim enable flag is typically set when the underlying device 208uses flash-memory as the device can use the delete command to 209pre-zero or at least avoid copying blocks that have been deleted. 210.Pp 211Note that this does not trim blocks that are already free. 212See the 213.Xr fsck_ffs 8 214.Fl E 215flag. 216.El 217.Pp 218At least one of these flags is required. 219.Sh FILES 220.Bl -tag -width ".Pa /etc/fstab" 221.It Pa /etc/fstab 222read this to determine the device file for a 223specified mount point. 224.El 225.Sh SEE ALSO 226.Xr fs 5 , 227.Xr dumpfs 8 , 228.Xr gjournal 8 , 229.Xr growfs 8 , 230.Xr newfs 8 231.Rs 232.%A M. McKusick 233.%A W. Joy 234.%A S. Leffler 235.%A R. Fabry 236.%T "A Fast File System for UNIX" 237.%J "ACM Transactions on Computer Systems 2" 238.%N 3 239.%P pp 181-197 240.%D August 1984 241.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 242.Re 243.Sh HISTORY 244The 245.Nm 246utility appeared in 247.Bx 4.2 . 248.Sh BUGS 249This utility does not work on active file systems. 250To change the root file system, the system must be rebooted 251after the file system is tuned. 252.\" Take this out and a Unix Daemon will dog your steps from now until 253.\" the time_t's wrap around. 254.Pp 255You can tune a file system, but you cannot tune a fish. 256