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Editing: tunefs.8
.\" Copyright (c) 1983, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)tunefs.8 8.2 (Berkeley) 12/11/93 .\" $FreeBSD$ .\" .Dd January 29, 2019 .Dt TUNEFS 8 .Os .Sh NAME .Nm tunefs .Nd tune up an existing UFS file system .Sh SYNOPSIS .Nm .Op Fl A .Op Fl a Cm enable | disable .Op Fl e Ar maxbpg .Op Fl f Ar avgfilesize .Op Fl j Cm enable | disable .Op Fl J Cm enable | disable .Op Fl k Ar held-for-metadata-blocks .Op Fl L Ar volname .Op Fl l Cm enable | disable .Op Fl m Ar minfree .Op Fl N Cm enable | disable .Op Fl n Cm enable | disable .Op Fl o Cm space | time .Op Fl p .Op Fl s Ar avgfpdir .Op Fl S Ar size .Op Fl t Cm enable | disable .Ar special | filesystem .Sh DESCRIPTION The .Nm utility is designed to change the dynamic parameters of a UFS file system which affect the layout policies. The .Nm utility cannot be run on an active file system. To change an active file system, it must be downgraded to read-only or unmounted. .Pp The parameters which are to be changed are indicated by the flags given below: .Bl -tag -width indent .It Fl A The file system has several backups of the super-block. Specifying this option will cause all backups to be modified as well as the primary super-block. This is potentially dangerous - use with caution. .It Fl a Cm enable | disable Turn on/off the administrative POSIX.1e ACL enable flag. .It Fl e Ar maxbpg Indicate the maximum number of blocks any single file can allocate out of a cylinder group before it is forced to begin allocating blocks from another cylinder group. Typically this value is set to about one quarter of the total blocks in a cylinder group. The intent is to prevent any single file from using up all the blocks in a single cylinder group, thus degrading access times for all files subsequently allocated in that cylinder group. The effect of this limit is to cause big files to do long seeks more frequently than if they were allowed to allocate all the blocks in a cylinder group before seeking elsewhere. For file systems with exclusively large files, this parameter should be set higher. .It Fl f Ar avgfilesize Specify the expected average file size. .It Fl j Cm enable | disable Turn on/off soft updates journaling. .It Fl J Cm enable | disable Turn on/off gjournal flag. .It Fl k Ar held-for-metadata-blocks Set the amount of space to be held for metadata blocks. When set, the file system preference routines will try to save the specified amount of space immediately following the inode blocks in each cylinder group for use by metadata blocks. Clustering the metadata blocks speeds up random file access and decreases the running time of .Xr fsck 8 . While this option can be set at any time, it is most effective if set before any data is loaded into the file system. By default .Xr newfs 8 sets it to half of the space reserved to minfree. .It Fl L Ar volname Add/modify an optional file system volume label. Legal characters are alphanumerics, dashes, and underscores. .It Fl l Cm enable | disable Turn on/off MAC multilabel flag. .It Fl m Ar minfree Specify the percentage of space held back from normal users; the minimum free space threshold. The default value used is 8%. Note that lowering the threshold can adversely affect performance: .Bl -bullet .It Settings of 5% and less force space optimization to always be used which will greatly increase the overhead for file writes. .It The file system's ability to avoid fragmentation will be reduced when the total free space, including the reserve, drops below 15%. As free space approaches zero, throughput can degrade by up to a factor of three over the performance obtained at a 10% threshold. .El .Pp If the value is raised above the current usage level, users will be unable to allocate files until enough files have been deleted to get under the higher threshold. .It Fl N Cm enable | disable Turn on/off the administrative NFSv4 ACL enable flag. .It Fl n Cm enable | disable Turn on/off soft updates. .It Fl o Cm space | time The file system can either try to minimize the time spent allocating blocks, or it can attempt to minimize the space fragmentation on the disk. Optimization for space has much higher overhead for file writes. The kernel normally changes the preference automatically as the percent fragmentation changes on the file system. .It Fl p Show a summary of what the current tunable settings are on the selected file system. More detailed information can be obtained from the .Xr dumpfs 8 utility. .It Fl s Ar avgfpdir Specify the expected number of files per directory. .It Fl S Ar size Specify the softdep journal size in bytes. The minimum is 4M. .It Fl t Cm enable | disable Turn on/off the TRIM enable flag. If enabled, and if the underlying device supports the BIO_DELETE command, the file system will send a delete request to the underlying device for each freed block. The trim enable flag is typically set when the underlying device uses flash-memory as the device can use the delete command to pre-zero or at least avoid copying blocks that have been deleted. .Pp Note that this does not trim blocks that are already free. See the .Xr fsck_ffs 8 .Fl E flag. .El .Pp At least one of these flags is required. .Sh FILES .Bl -tag -width ".Pa /etc/fstab" .It Pa /etc/fstab read this to determine the device file for a specified mount point. .El .Sh SEE ALSO .Xr fs 5 , .Xr dumpfs 8 , .Xr gjournal 8 , .Xr growfs 8 , .Xr newfs 8 .Rs .%A M. McKusick .%A W. Joy .%A S. Leffler .%A R. Fabry .%T "A Fast File System for UNIX" .%J "ACM Transactions on Computer Systems 2" .%N 3 .%P pp 181-197 .%D August 1984 .%O "(reprinted in the BSD System Manager's Manual, SMM:5)" .Re .Sh HISTORY The .Nm utility appeared in .Bx 4.2 . .Sh BUGS This utility does not work on active file systems. To change the root file system, the system must be rebooted after the file system is tuned. .\" Take this out and a Unix Daemon will dog your steps from now until .\" the time_t's wrap around. .Pp You can tune a file system, but you cannot tune a fish.
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