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 135to run background fsck on filesystems enabled for journaling. 136.It Fl J Cm enable | disable 137Turn on/off gjournal flag. 138.It Fl k Ar held-for-metadata-blocks 139Set the amount of space to be held for metadata blocks. 140When set, the file system preference routines will try to save 141the specified amount of space immediately following the inode blocks 142in each cylinder group for use by metadata blocks. 143Clustering the metadata blocks speeds up random file access 144and decreases the running time of 145.Xr fsck 8 . 146While this option can be set at any time, 147it is most effective if set before any data is loaded into the file system. 148By default 149.Xr newfs 8 150sets it to half of the space reserved to minfree. 151.It Fl L Ar volname 152Add/modify an optional file system volume label. 153Legal characters are alphanumerics, dashes, and underscores. 154.It Fl l Cm enable | disable 155Turn on/off MAC multilabel flag. 156.It Fl m Ar minfree 157Specify the percentage of space held back 158from normal users; the minimum free space threshold. 159The default value used is 8%. 160Note that lowering the threshold can adversely affect performance: 161.Bl -bullet 162.It 163Settings of 5% and less force space optimization to 164always be used which will greatly increase the overhead for file 165writes. 166.It 167The file system's ability to avoid fragmentation will be reduced 168when the total free space, including the reserve, drops below 15%. 169As free space approaches zero, throughput can degrade by up to a 170factor of three over the performance obtained at a 10% threshold. 171.El 172.Pp 173If the value is raised above the current usage level, 174users will be unable to allocate files until enough files have 175been deleted to get under the higher threshold. 176.It Fl N Cm enable | disable 177Turn on/off the administrative NFSv4 ACL enable flag. 178.It Fl n Cm enable | disable 179Turn on/off soft updates. 180.It Fl o Cm space | time 181The file system can either try to minimize the time spent 182allocating blocks, or it can attempt to minimize the space 183fragmentation on the disk. 184Optimization for space has much 185higher overhead for file writes. 186The kernel normally changes the preference automatically as 187the percent fragmentation changes on the file system. 188.It Fl p 189Show a summary of what the current tunable settings 190are on the selected file system. 191More detailed information can be 192obtained from the 193.Xr dumpfs 8 194utility. 195.It Fl s Ar avgfpdir 196Specify the expected number of files per directory. 197.It Fl S Ar size 198Specify the softdep journal size in bytes. 199The minimum is 4M. 200.It Fl t Cm enable | disable 201Turn on/off the TRIM enable flag. 202If enabled, and if the underlying device supports the BIO_DELETE 203command, the file system will send a delete request to the underlying 204device for each freed block. 205The trim enable flag is typically set when the underlying device 206uses flash-memory as the device can use the delete command to 207pre-zero or at least avoid copying blocks that have been deleted. 208.Pp 209Note that this does not trim blocks that are already free. 210See the 211.Xr fsck_ffs 8 212.Fl E 213flag. 214.El 215.Pp 216At least one of these flags is required. 217.Sh FILES 218.Bl -tag -width ".Pa /etc/fstab" 219.It Pa /etc/fstab 220read this to determine the device file for a 221specified mount point. 222.El 223.Sh SEE ALSO 224.Xr fs 5 , 225.Xr dumpfs 8 , 226.Xr gjournal 8 , 227.Xr growfs 8 , 228.Xr newfs 8 229.Rs 230.%A M. McKusick 231.%A W. Joy 232.%A S. Leffler 233.%A R. Fabry 234.%T "A Fast File System for UNIX" 235.%J "ACM Transactions on Computer Systems 2" 236.%N 3 237.%P pp 181-197 238.%D August 1984 239.%O "(reprinted in the BSD System Manager's Manual, SMM:5)" 240.Re 241.Sh HISTORY 242The 243.Nm 244utility appeared in 245.Bx 4.2 . 246.Sh BUGS 247This utility does not work on active file systems. 248To change the root file system, the system must be rebooted 249after the file system is tuned. 250.\" Take this out and a Unix Daemon will dog your steps from now until 251.\" the time_t's wrap around. 252.Pp 253You can tune a file system, but you cannot tune a fish. 254