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.\" 30.Dd August 16, 2022 31.Dt TUNEFS 8 32.Os 33.Sh NAME 34.Nm tunefs 35.Nd tune up an existing UFS file system 36.Sh SYNOPSIS 37.Nm 38.Op Fl A 39.Op Fl a Cm enable | disable 40.Op Fl e Ar maxbpg 41.Op Fl f Ar avgfilesize 42.Op Fl j Cm enable | disable 43.Op Fl J Cm enable | disable 44.Op Fl k Ar held-for-metadata-blocks 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.Pp 98Enabling journaling reduces the time spent by 99.Xr fsck_ffs 8 100cleaning up a filesystem after a crash to a few seconds from minutes to hours. 101Without journaling, the time to recover after a crash is a function 102of the number of files in the filesystem and the size of the filesystem. 103With journaling, the time to recover after a crash is a function of the 104amount of activity in the filesystem in the minute before the crash. 105Journaled recovery time is usually only a few seconds and never 106exceeds a minute. 107.Pp 108The drawback to using journaling is that the writes to its log adds 109an extra write load to the media containing the filesystem. 110Thus a write-intensive workload will have reduced throughput on a 111filesystem running with journaling. 112.Pp 113Like all journaling filesystems, the journal recovery will only fix 114issues known to the journal. 115Specifically if a media error occurs, 116the journal will not know about it and hence will not fix it. 117Thus when using journaling, it is still necessary to run a full fsck 118every few months or after a filesystem panic to check for and fix 119any errors brought on by media failure. 120A full fsck can be done by running a background fsck on a live 121filesystem or by running with the 122.Fl f 123flag on an unmounted filesystem. 124When running 125.Xr fsck_ffs 8 126in background on a live filesystem the filesystem performance 127will be about half of normal during the time that the background 128.Xr fsck_ffs 8 129is running. 130Running a full fsck on a UFS filesystem is the equivalent of 131running a scrub on a ZFS filesystem. 132.It Fl J Cm enable | disable 133Turn on/off gjournal flag. 134.It Fl k Ar held-for-metadata-blocks 135Set the amount of space to be held for metadata blocks. 136When set, the file system preference routines will try to save 137the specified amount of space immediately following the inode blocks 138in each cylinder group for use by metadata blocks. 139Clustering the metadata blocks speeds up random file access 140and decreases the running time of 141.Xr fsck 8 . 142While this option can be set at any time, 143it is most effective if set before any data is loaded into the file system. 144By default 145.Xr newfs 8 146sets it to half of the space reserved to minfree. 147.It Fl L Ar volname 148Add/modify an optional file system volume label. 149Legal characters are alphanumerics, dashes, and underscores. 150.It Fl l Cm enable | disable 151Turn on/off MAC multilabel flag. 152.It Fl m Ar minfree 153Specify the percentage of space held back 154from normal users; the minimum free space threshold. 155The default value used is 8%. 156Note that lowering the threshold can adversely affect performance: 157.Bl -bullet 158.It 159Settings of 5% and less force space optimization to 160always be used which will greatly increase the overhead for file 161writes. 162.It 163The file system's ability to avoid fragmentation will be reduced 164when the total free space, including the reserve, drops below 15%. 165As free space approaches zero, throughput can degrade by up to a 166factor of three over the performance obtained at a 10% threshold. 167.El 168.Pp 169If the value is raised above the current usage level, 170users will be unable to allocate files until enough files have 171been deleted to get under the higher threshold. 172.It Fl N Cm enable | disable 173Turn on/off the administrative NFSv4 ACL enable flag. 174.It Fl n Cm enable | disable 175Turn on/off soft updates. 176.It Fl o Cm space | time 177The file system can either try to minimize the time spent 178allocating blocks, or it can attempt to minimize the space 179fragmentation on the disk. 180Optimization for space has much 181higher overhead for file writes. 182The kernel normally changes the preference automatically as 183the percent fragmentation changes on the file system. 184.It Fl p 185Show a summary of what the current tunable settings 186are on the selected file system. 187More detailed information can be 188obtained from the 189.Xr dumpfs 8 190utility. 191.It Fl s Ar avgfpdir 192Specify the expected number of files per directory. 193.It Fl S Ar size 194Specify the softdep journal size in bytes. 195The minimum is 4M. 196.It Fl t Cm enable | disable 197Turn on/off the TRIM enable flag. 198If enabled, and if the underlying device supports the BIO_DELETE 199command, the file system will send a delete request to the underlying 200device for each freed block. 201The trim enable flag is typically set when the underlying device 202uses flash-memory as the device can use the delete command to 203pre-zero or at least avoid copying blocks that have been deleted. 204.Pp 205Note that this does not trim blocks that are already free. 206See the 207.Xr fsck_ffs 8 208.Fl E 209flag. 210.El 211.Pp 212At least one of these flags is required. 213.Sh FILES 214.Bl -tag -width ".Pa /etc/fstab" 215.It Pa /etc/fstab 216read this to determine the device file for a 217specified mount point. 218.El 219.Sh SEE ALSO 220.Xr fs 5 , 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