78f4129876
All the needed infrastructure updates have been made to allow snapshots to be taken on UFS/FFS filesystems that are using journaled soft updates. The most immediate benefit is the ability to use a snapshot to take a consistent filesystem dump on a live filesystem using the -L option to dump(8). Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D36491
254 lines
9.0 KiB
Groff
254 lines
9.0 KiB
Groff
.\" Copyright (c) 1983, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)tunefs.8 8.2 (Berkeley) 12/11/93
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.\" $FreeBSD$
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.\"
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.Dd August 16, 2022
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.Dt TUNEFS 8
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.Os
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.Sh NAME
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.Nm tunefs
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.Nd tune up an existing UFS file system
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.Sh SYNOPSIS
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.Nm
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.Op Fl A
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.Op Fl a Cm enable | disable
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.Op Fl e Ar maxbpg
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.Op Fl f Ar avgfilesize
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.Op Fl j Cm enable | disable
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.Op Fl J Cm enable | disable
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.Op Fl k Ar held-for-metadata-blocks
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.Op Fl L Ar volname
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.Op Fl l Cm enable | disable
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.Op Fl m Ar minfree
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.Op Fl N Cm enable | disable
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.Op Fl n Cm enable | disable
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.Op Fl o Cm space | time
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.Op Fl p
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.Op Fl s Ar avgfpdir
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.Op Fl S Ar size
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.Op Fl t Cm enable | disable
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.Ar special | filesystem
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.Sh DESCRIPTION
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The
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.Nm
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utility is designed to change the dynamic parameters of a UFS file system
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which affect the layout policies.
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The
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.Nm
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utility cannot be run on an active file system.
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To change an active file system,
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it must be downgraded to read-only or unmounted.
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.Pp
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The parameters which are to be changed are indicated by the flags
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given below:
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.Bl -tag -width indent
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.It Fl A
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The file system has several backups of the super-block.
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Specifying
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this option will cause all backups to be modified as well as the
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primary super-block.
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This is potentially dangerous - use with caution.
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.It Fl a Cm enable | disable
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Turn on/off the administrative POSIX.1e ACL enable flag.
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.It Fl e Ar maxbpg
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Indicate the maximum number of blocks any single file can
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allocate out of a cylinder group before it is forced to begin
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allocating blocks from another cylinder group.
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Typically this value is set to about one quarter of the total blocks
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in a cylinder group.
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The intent is to prevent any single file from using up all the
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blocks in a single cylinder group,
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thus degrading access times for all files subsequently allocated
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in that cylinder group.
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The effect of this limit is to cause big files to do long seeks
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more frequently than if they were allowed to allocate all the blocks
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in a cylinder group before seeking elsewhere.
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For file systems with exclusively large files,
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this parameter should be set higher.
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.It Fl f Ar avgfilesize
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Specify the expected average file size.
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.It Fl j Cm enable | disable
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Turn on/off soft updates journaling.
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.Pp
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Enabling journaling reduces the time spent by
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.Xr fsck_ffs 8
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cleaning up a filesystem after a crash to a few seconds from minutes to hours.
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Without journaling, the time to recover after a crash is a function
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of the number of files in the filesystem and the size of the filesystem.
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With journaling, the time to recover after a crash is a function of the
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amount of activity in the filesystem in the minute before the crash.
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Journaled recovery time is usually only a few seconds and never
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exceeds a minute.
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.Pp
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The drawback to using journaling is that the writes to its log adds
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an extra write load to the media containing the filesystem.
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Thus a write-intensive workload will have reduced throughput on a
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filesystem running with journaling.
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.Pp
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Like all journaling filesystems, the journal recovery will only fix
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issues known to the journal.
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Specifically if a media error occurs,
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the journal will not know about it and hence will not fix it.
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Thus when using journaling, it is still necessary to run a full fsck
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every few months or after a filesystem panic to check for and fix
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any errors brought on by media failure.
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A full fsck can be done by running a background fsck on a live
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filesystem or by running with the
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.Fl f
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flag on an unmounted filesystem.
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When running
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.Xr fsck_ffs 8
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in background on a live filesystem the filesystem performance
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will be about half of normal during the time that the background
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.Xr fsck_ffs 8
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is running.
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Running a full fsck on a UFS filesystem is the equivalent of
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running a scrub on a ZFS filesystem.
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.Pp
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Presently it is not possible
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to run background fsck on filesystems enabled for journaling.
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.It Fl J Cm enable | disable
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Turn on/off gjournal flag.
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.It Fl k Ar held-for-metadata-blocks
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Set the amount of space to be held for metadata blocks.
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When set, the file system preference routines will try to save
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the specified amount of space immediately following the inode blocks
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in each cylinder group for use by metadata blocks.
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Clustering the metadata blocks speeds up random file access
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and decreases the running time of
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.Xr fsck 8 .
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While this option can be set at any time,
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it is most effective if set before any data is loaded into the file system.
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By default
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.Xr newfs 8
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sets it to half of the space reserved to minfree.
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.It Fl L Ar volname
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Add/modify an optional file system volume label.
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Legal characters are alphanumerics, dashes, and underscores.
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.It Fl l Cm enable | disable
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Turn on/off MAC multilabel flag.
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.It Fl m Ar minfree
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Specify the percentage of space held back
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from normal users; the minimum free space threshold.
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The default value used is 8%.
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Note that lowering the threshold can adversely affect performance:
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.Bl -bullet
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.It
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Settings of 5% and less force space optimization to
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always be used which will greatly increase the overhead for file
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writes.
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.It
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The file system's ability to avoid fragmentation will be reduced
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when the total free space, including the reserve, drops below 15%.
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As free space approaches zero, throughput can degrade by up to a
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factor of three over the performance obtained at a 10% threshold.
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.El
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.Pp
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If the value is raised above the current usage level,
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users will be unable to allocate files until enough files have
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been deleted to get under the higher threshold.
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.It Fl N Cm enable | disable
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Turn on/off the administrative NFSv4 ACL enable flag.
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.It Fl n Cm enable | disable
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Turn on/off soft updates.
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.It Fl o Cm space | time
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The file system can either try to minimize the time spent
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allocating blocks, or it can attempt to minimize the space
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fragmentation on the disk.
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Optimization for space has much
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higher overhead for file writes.
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The kernel normally changes the preference automatically as
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the percent fragmentation changes on the file system.
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.It Fl p
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Show a summary of what the current tunable settings
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are on the selected file system.
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More detailed information can be
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obtained from the
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.Xr dumpfs 8
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utility.
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.It Fl s Ar avgfpdir
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Specify the expected number of files per directory.
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.It Fl S Ar size
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Specify the softdep journal size in bytes.
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The minimum is 4M.
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.It Fl t Cm enable | disable
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Turn on/off the TRIM enable flag.
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If enabled, and if the underlying device supports the BIO_DELETE
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command, the file system will send a delete request to the underlying
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device for each freed block.
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The trim enable flag is typically set when the underlying device
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uses flash-memory as the device can use the delete command to
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pre-zero or at least avoid copying blocks that have been deleted.
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.Pp
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Note that this does not trim blocks that are already free.
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See the
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.Xr fsck_ffs 8
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.Fl E
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flag.
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.El
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.Pp
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At least one of these flags is required.
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.Sh FILES
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.Bl -tag -width ".Pa /etc/fstab"
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.It Pa /etc/fstab
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read this to determine the device file for a
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specified mount point.
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.El
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.Sh SEE ALSO
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.Xr fs 5 ,
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.Xr dumpfs 8 ,
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.Xr gjournal 8 ,
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.Xr growfs 8 ,
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.Xr newfs 8
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.Rs
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.%A M. McKusick
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.%A W. Joy
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.%A S. Leffler
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.%A R. Fabry
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.%T "A Fast File System for UNIX"
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.%J "ACM Transactions on Computer Systems 2"
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.%N 3
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.%P pp 181-197
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.%D August 1984
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.%O "(reprinted in the BSD System Manager's Manual, SMM:5)"
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.Re
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.Sh HISTORY
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The
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.Nm
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utility appeared in
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.Bx 4.2 .
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.Sh BUGS
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This utility does not work on active file systems.
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To change the root file system, the system must be rebooted
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after the file system is tuned.
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.\" Take this out and a Unix Daemon will dog your steps from now until
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.\" the time_t's wrap around.
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.Pp
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You can tune a file system, but you cannot tune a fish.
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