55abc5794a
We pretend we have one head with two megabyte worth of sectors per cylinder. The code try to access another head in what it belives to the same physical cylinder, because it belives that it would be faster than waiting for the next free sector under this head to come around. Most modern drives doesn't have a "classical" geometry, and thus we end up fooling ourselves doing the above optimization. With this change we will fill a cylinder sequentially if we can, and thus get much more mileage from the track-buffer/cache built into the drives. As a result a lot of seeks to the next or previous track should be avoided by this. (My disk is a lot less noisy actually...) You can still get the old behaviour, by specifying zero for the numbers. This will also solve the problem with newfs barfing at really big drives. Obtained from: adult advice from Kirk.
299 lines
9.7 KiB
Groff
299 lines
9.7 KiB
Groff
.\" Copyright (c) 1983, 1987, 1991, 1993, 1994
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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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" @(#)newfs.8 8.3 (Berkeley) 3/27/94
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.\"
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.Dd March 27, 1994
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.Dt NEWFS 8
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.Os BSD 4.2
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.Sh NAME
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.Nm newfs ,
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.Nm mfs
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.Nd construct a new file system
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.Sh SYNOPSIS
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.Nm newfs
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.Op Fl NO
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.Op Fl S Ar sector-size
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.Op Fl a Ar maxcontig
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.Op Fl b Ar block-size
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.Op Fl c Ar cylinders
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.Op Fl d Ar rotdelay
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.Op Fl e Ar maxbpg
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.Op Fl f Ar frag-size
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.Op Fl i Ar bytes
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.Op Fl k Ar skew
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.Op Fl l Ar interleave
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.Op Fl m Ar free space
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.Op Fl o Ar optimization
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.Op Fl p Ar sectors
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.Op Fl r Ar revolutions
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.Op Fl s Ar size
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.Op Fl t Ar tracks
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.Op Fl u Ar sectors
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.Op Fl x Ar sectors
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.Ar special
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.Nm mount_mfs
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.Op Fl N
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.Op Fl F Ar file
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.Op Fl T Ar disktype
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.Op Fl a Ar maxcontig
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.Op Fl b Ar block-size
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.Op Fl c Ar cylinders
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.Op Fl d Ar rotdelay
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.Op Fl e Ar maxbpg
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.Op Fl f Ar frag-size
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.Op Fl i Ar bytes
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.Op Fl m Ar free space
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.Op Fl o Ar options
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.Op Fl s Ar size
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.Ar special node
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.Sh DESCRIPTION
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.Nm Newfs
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replaces the more obtuse
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.Xr mkfs 8
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program.
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Before running
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.Nm newfs
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or
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.Nm mount_mfs ,
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the disk must be labeled using
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.Xr disklabel 8 .
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.Nm Newfs
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builds a file system on the specified special device.
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Typically the defaults are reasonable, however
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.Nm newfs
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has numerous options to allow the defaults to be selectively overridden.
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.Pp
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.Nm Mount_mfs
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is used to build a file system in virtual memory and then mount it
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on a specified node.
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.Nm Mount_mfs
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exits and the contents of the file system are lost
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when the file system is unmounted.
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If
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.Nm mount_mfs
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is sent a signal while running,
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for example during system shutdown,
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it will attempt to unmount its
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corresponding file system.
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The parameters to
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.Nm mount_mfs
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are the same as those to
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.Nm newfs .
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The special file is only used to read the disk label which provides
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a set of configuration parameters for the memory based file system.
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The special file is typically that of the primary swap area,
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since that is where the file system will be backed up when
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free memory gets low and the memory supporting
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the file system has to be paged.
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.Pp
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The following options define the general layout policies.
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.Bl -tag -width Fl
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.It Fl T Ar disktype
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For backward compatibility and for
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.Nm mount_mfs .
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.It Fl F Ar file
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.Nm mount_mfs
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will use this file for the image of the filesystem. When
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.Nm mount_mfs
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exits, this file will be left behind.
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.It Fl N
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Causes the file system parameters to be printed out
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without really creating the file system.
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.It Fl O
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Creates a 4.3BSD format filesystem.
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This options is primarily used to build root filesystems
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that can be understood by older boot ROMs.
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.It Fl a Ar maxcontig
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This specifies the maximum number of contiguous blocks that will be
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laid out before forcing a rotational delay (see the
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.Fl d
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option).
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The default value is one.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl b Ar block-size
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The block size of the file system, in bytes.
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.It Fl c Ar #cylinders/group
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The number of cylinders per cylinder group in a file system.
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The default value is 16.
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.It Fl d Ar rotdelay
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This specifies the expected time (in milliseconds) to service a transfer
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completion interrupt and initiate a new transfer on the same disk.
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The default is 0 milliseconds.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl e Ar maxbpg
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This indicates 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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The default is about one quarter of the total blocks in a cylinder group.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl f Ar frag-size
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The fragment size of the file system in bytes.
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.It Fl i Ar number of bytes per inode
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This specifies the density of inodes in the file system.
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The default is to create an inode for each 2048 bytes of data space.
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If fewer inodes are desired, a larger number should be used;
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to create more inodes a smaller number should be given.
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.It Fl m Ar free space \&%
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The percentage of space reserved from normal users; the minimum free
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space threshold.
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The default value used is 10%.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl n Ar number of distinguished rotational positions
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Determines how many rotational time slots there are in one revolution of
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the disk. Defaults to 1, which escentially disables the rotational position table.
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.It Fl o Ar optimization\ preference
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.Pq ``space'' or ``time''
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The file system can either be instructed to try to minimize the time spent
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allocating blocks, or to try to minimize the space fragmentation on the disk.
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If the value of minfree (see above) is less than 10%,
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the default is to optimize for space;
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if the value of minfree is greater than or equal to 10%,
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the default is to optimize for time.
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See
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.Xr tunefs 8
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for more details on how to set this option.
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.It Fl s Ar size
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The size of the file system in sectors.
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.El
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.Pp
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The following options override the standard sizes for the disk geometry.
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Their default values are taken from the disk label.
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Changing these defaults is useful only when using
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.Nm newfs
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to build a file system whose raw image will eventually be used on a
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different type of disk than the one on which it is initially created
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(for example on a write-once disk).
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Note that changing any of these values from their defaults will make
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it impossible for
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.Xr fsck
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to find the alternate superblocks if the standard superblock is lost.
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.Bl -tag -width Fl
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.It Fl S Ar sector-size
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The size of a sector in bytes (almost never anything but 512).
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.It Fl k Ar sector \&0 skew , per track
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Used to describe perturbations in the media format to compensate for
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a slow controller.
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Track skew is the offset of sector 0 on track N relative to sector 0
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on track N-1 on the same cylinder.
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.It Fl l Ar hardware sector interleave
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Used to describe perturbations in the media format to compensate for
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a slow controller.
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Interleave is physical sector interleave on each track,
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specified as the denominator of the ratio:
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.Dl sectors read/sectors passed over
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Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies
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logical sector 0 is separated by one sector from logical sector 1.
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.It Fl p Ar spare sectors per track
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Spare sectors (bad sector replacements) are physical sectors that occupy
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space at the end of each track.
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They are not counted as part of the sectors/track
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.Pq Fl u
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since they are not available to the file system for data allocation.
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.It Fl r Ar revolutions/minute
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The speed of the disk in revolutions per minute.
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.It Fl t Ar #tracks/cylinder
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The number of tracks/cylinder available for data allocation by the file
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system.
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The default is 1.
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If zero is specified, the value from the disklabel will be used.
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.It Fl u Ar sectors/track
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The number of sectors per track available for data allocation by the file
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system.
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The default is 4096.
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If zero is specified, the value from the disklabel will be used.
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This does not include sectors reserved at the end of each track for bad
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block replacement (see the
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.Fl p
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option.)
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.It Fl x Ar spare sectors per cylinder
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Spare sectors (bad sector replacements) are physical sectors that occupy
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space at the end of the last track in the cylinder.
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They are deducted from the sectors/track
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.Pq Fl u
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of the last track of each cylinder since they are not available to the file
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system for data allocation.
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.El
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.Pp
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The options to the
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.Nm mount_mfs
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command are as described for the
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.Nm newfs
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command, except for the
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.Fl o
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option.
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.Pp
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That option is as follows:
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.Bl -tag -width indent
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.It Fl o
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Options are specified with a
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.Fl o
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flag followed by a comma separated string of options.
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See the
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.Xr mount 8
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man page for possible options and their meanings.
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.El
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.Sh SEE ALSO
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.Xr disktab 5 ,
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.Xr fs 5 ,
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.Xr dumpfs 8 ,
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.Xr disklabel 8 ,
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.Xr diskpart 8 ,
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.Xr fsck 8 ,
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.Xr format 8 ,
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.Xr mount 8 ,
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.Xr tunefs 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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.%V 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)
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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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command appeared in
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.Bx 4.2 .
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