282 lines
7.8 KiB
Groff
282 lines
7.8 KiB
Groff
.\" $NetBSD: mount_mfs.8,v 1.16 2010/02/18 14:00:39 wiz Exp $
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.\"
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.\" 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. 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 8.6 (Berkeley) 5/3/95
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.\"
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.Dd December 8, 2007
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.Dt MOUNT_MFS 8
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.Os
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.Sh NAME
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.Nm mount_mfs
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.Nd mount a memory based file system
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.Sh SYNOPSIS
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.Nm mount_mfs
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.Op Fl N
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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 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 g Ar groupname
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.Op Fl i Ar bytes-per-inode
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.Op Fl m Ar free-space
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.Op Fl n Ar inodes
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.Op Fl o Ar options
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.Op Fl p Ar permissions
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.Op Fl s Ar size
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.Op Fl u Ar username
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.Op Fl V Ar verbose
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.Ar special node
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.Sh DESCRIPTION
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.Nm
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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
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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
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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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.Ar special
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is ignored.
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.Pp
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Options with numeric arguments may contain an optional (case-insensitive)
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suffix:
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.Bl -tag -width 3n -offset indent -compact
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.It b
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Bytes; causes no modification.
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(Default)
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.It k
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Kilo; multiply the argument by 1024
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.It m
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Mega; multiply the argument by 1048576
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.It g
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Giga; multiply the argument by 1073741824
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.El
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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 N
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Causes the memory file system parameters to be printed out
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without really mounting the memory file system.
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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 8.
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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 must be a power of two.
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The smallest allowable size is 4096 bytes.
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The default size depends upon the size of the file system:
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.Pp
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.Bl -tag -width "file system size" -compact -offset indent
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.It Sy "file system size"
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.Ar block-size
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.It \&\*[Lt] 20 MB
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4 KB
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.It \&\*[Lt] 1024 MB
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8 KB
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.It \&\*[Gt]\&= 1024 MB
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16 KB
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.El
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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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.ne 1i
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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 must be a power of two ranging in value between
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.Ar block-size Ns /8
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and
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.Ar block-size .
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The optimal
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.Ar block-size : Ns Ar frag-size
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ratio is 8:1.
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Other ratios are possible, but are not recommended,
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and may produce unpredictable results.
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The default size depends upon the size of the file system:
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.Pp
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.Bl -tag -width "file system size" -compact -offset indent
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.It Sy "file system size"
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.Ar frag-size
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.It \&\*[Lt] 20 MB
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0.5 KB
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.It \&\*[Lt] 1024 MB
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1 KB
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.It \&\*[Gt]\&= 1024 MB
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2 KB
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.El
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.It Fl g Ar groupname
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This specifies the group name or group id of the root
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inode of the file system.
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.It Fl i Ar bytes-per-inode
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This specifies the density of inodes in the file system.
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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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The default is to create an inode for every
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.Pq 4 * Ar frag-size
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bytes of data space:
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.Pp
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.Bl -tag -width "file system size" -compact -offset indent
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.It Sy "file system size"
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.Ar bytes-per-inode
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.It \&\*[Lt] 20 MB
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2 KB
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.It \&\*[Lt] 1024 MB
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4 KB
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.It \&\*[Gt]\&= 1024 MB
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8 KB
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.El
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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 5%.
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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 inodes
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This specifies the number of inodes for the filesystem.
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If both
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.Fl i
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and
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.Fl n
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are specified then
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.Fl n
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takes precedence.
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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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.It Fl p Ar permissions
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This specifies the permissions of the root
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inode of the file system.
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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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An
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.Sq s
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suffix will be interpreted as the number of sectors (the default).
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All other suffixes are interpreted as per other numeric arguments,
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except that the number is converted into sectors by dividing by the
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default sector size (which is 512 bytes)
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after suffix interpretation.
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.It Fl u Ar username
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This specifies the user name or user id of the root
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inode of the file system.
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.It Fl V Ar verbose
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This controls the amount of information written to stdout:
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.Bl -tag -width 3n -offset indent -compact
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.It 0
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No output
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.It 1
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Overall size and cylinder group details.
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.It 2
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A progress bar (dots ending at right hand margin).
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.It 3
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The first few super-block backup sector numbers are displayed before the
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progress bar.
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.It 4
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All the super-block backup sector numbers are displayed (no progress bar).
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.El
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The default is 0.
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If
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.Fl N
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is specified
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.Nm
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stops before outputting the progress bar.
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.El
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.Sh NOTES
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The owner and group ids of the root node of the new file system
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are set to the effective uid and gid of the user mounting
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the file system.
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.Sh EXAMPLES
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Mount a 32 MB mfs on /tmp:
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.Pp
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.Dl mount_mfs -s 32m swap /tmp
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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 disklabel 8 ,
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.Xr diskpart 8 ,
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.Xr dumpfs 8 ,
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.\" .Xr format 8 ,
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.Xr fsck_ffs 8 ,
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.Xr fsirand 8 ,
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.Xr mount 8 ,
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.Xr newfs 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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.Sh BUGS
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The
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.Cm async
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.Xr mount 8
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option is currently disabled in this file system because it causes
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hangs when writing lots of data.
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The problem is that MFS needs to allocate pages to clean pages, so if
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it waits until the last minute to clean pages then there may not be
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any of them available to do the cleaning.
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