167 lines
5.7 KiB
Groff
167 lines
5.7 KiB
Groff
.\" 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. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. 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 May 18, 2002
|
|
.Dt TUNEFS 8
|
|
.Os
|
|
.Sh NAME
|
|
.Nm tunefs
|
|
.Nd tune up an existing file system
|
|
.Sh SYNOPSIS
|
|
.Nm
|
|
.Op Fl A
|
|
.Op Fl e Ar maxbpg
|
|
.Op Fl f Ar avgfilesize
|
|
.Op Fl m Ar minfree
|
|
.Op Fl n Cm enable | disable
|
|
.Op Fl o Cm space | time
|
|
.Op Fl p
|
|
.Op Fl s Ar avgfpdir
|
|
.Ar special | filesystem
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
utility is designed to change the dynamic parameters of a 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 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 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 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
|
|
or
|
|
.Xr ffsinfo 8
|
|
utilities.
|
|
.It Fl s Ar avgfpdir
|
|
Specify the expected number of files per directory.
|
|
.El
|
|
.Pp
|
|
At least one of the above 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 ffsinfo 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 BUGS
|
|
This utility should work on active file systems.
|
|
.\" 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 can't tune a fish.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
utility appeared in
|
|
.Bx 4.2 .
|