261 lines
8.4 KiB
Groff
261 lines
8.4 KiB
Groff
.\" Copyright (c) 1993 University of Utah.
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.\" Copyright (c) 1980, 1989, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the Systems Programming Group of the University of Utah Computer
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.\" Science Department.
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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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.\" @(#)vnconfig.8 8.1 (Berkeley) 6/5/93
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.\" $FreeBSD$
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.\"
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.Dd July 8, 1993
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.Dt VNCONFIG 8
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.Os BSD 4
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.Sh NAME
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.Nm vnconfig
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.Nd configure and enable vnode disks
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.Sh SYNOPSIS
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.Nm vnconfig
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.Op Fl cdeguv
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.Op Fl s Ar option[,option...]
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.Op Fl r Ar option[,option...]
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.Op Fl S Ar value
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.Ar special_file Ar [regular_file]
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.Op Ar feature
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.Nm vnconfig
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.Fl a
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.Op Fl cdeguv
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.Op Fl s Ar option
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.Op Fl r Ar option
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.Op Fl f Ar config_file
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.Sh DESCRIPTION
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The
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.Nm
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command configures and enables vnode pseudo disk devices.
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The first form of the command will associate the special file
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.Ar special_file
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with the regular file
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.Ar regular_file
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allowing the latter to be accessed as though it were a disk.
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Hence a regular file within the filesystem can be used for swapping
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or can contain a filesystem that is mounted in the name space. If you
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want to use swap backing store for your device instead of a file, you
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can leave regular_file out and specify the size of the block device
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with the -S option.
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.Pp
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Options indicate an action to be performed:
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.Bl -tag -width indent
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.It Fl a
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Read a command file and performs the
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specified actions for each device/file pair.
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.It Fl c
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Configure the device.
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If successful, references to
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.Ar special_file
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will access the contents of
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.Ar regular_file .
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.It Fl d
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Disable (if possible) the specified feature.
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.It Fl e
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Configure the device and enables any
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.Ar feature
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that was specified.
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If no feature was specified,
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.Fl e
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is the same as
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.Fl c .
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.It Fl f Ar config_file
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Use
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.Ar config_file
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as an alternate config file.
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.It Fl g
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Fiddle global options.
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.It Fl r Ar flag
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Reset
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.Ar flag .
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The list of allowed flags and their meanings are:
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.Bl -tag -width "follow"
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.It Ar labels
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use disk/slice labels.
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.It Ar reserve
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Pre-reserve the blocks underlying the file or swap backing store. Currently only
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works for swap backing store. This option also disables on-the-fly freeing of
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the underlying backing store (for example, when you remove a large file).
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Use this option if you wish to avoid long-term fragmentation of the backing
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store. Also note that when this option is used, the initial contents of the
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backing store may contain garbage rather then zeros. It may even be possible to
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recover the prior contents of a swap-backed VN across a reboot if the VN device
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is configured before any swap is allocated by the system.
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.It Ar follow
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debug flow in the
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.Xr vn 4
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driver.
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.It Ar debug
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debug data in the
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.Xr vn 4
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driver.
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.It Ar io
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debug I/O in the
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.Xr vn 4
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driver.
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.It Ar all
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turn on all flags.
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.It Ar none
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turn off all flags.
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.El
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.It Fl s Ar flag
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Set
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.Ar flag .
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The list of allowed flags and their meanings are the same as for the
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.Fl r
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option.
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.It Fl S Ar value{k,m,g,t}
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If no regular file is specified, VN will use swap for backing store.
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This option specifies the size of the device. For example, '23m' for
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23 megabytes. The VN device will round the size up to a machine page boundary.
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Filesystems up to 7.9 terabytes are supported. When specified along with
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a regular file, this option overrides the regular file's size insofar as
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VN is concerned.
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.It Fl T
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When a regular file is specified, VN will ftruncate() the file to 0 first.
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Normally you should also specify the -S option to set the size of the file.
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This option also creates the file if it did not previously exist.
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This option is only meaningful if the -S option has been specified.
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.It Fl Z
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When a regular file is specified, VN will zero the contents of the file to
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ensure that all blocks have been allocated by the filesystem. This option is
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only meaningful if the -S option has been specified.
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.It Fl u
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Disable and ``unconfigure'' the device.
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.It Fl v
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Print messages to stdout describing actions taken.
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.El
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.Pp
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If no action option is given,
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.Fl c
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is assumed.
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.Pp
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The
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.Ar feature
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argument specifies a feature that can be enabled via the
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.Fl e
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option:
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.Bl -tag -width indent
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.It Dv swap
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Swapping is enabled on the special file.
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See
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.Xr swapon 2 .
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.It Dv Pf mountro= Pa mount_point
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The special file is mounted read-only on
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.Ar mount_point .
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See
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.Xr mount 2 .
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.It Dv Pf mountrw= Pa mount_point
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The special file is mounted read-write on
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.Ar mount_point .
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See
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.Xr mount 2 .
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.It Dv Pf mount= Pa mount_point
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Same as ``mountrw=''.
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.El
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.Pp
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A configuration file contains one line per device/file pair in the form:
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.Bd -literal
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special_file regular_file [ feature ]
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.Ed
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.Pp
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where fields are separated by white space.
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The previously described action options serve to configure, enable,
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disable or unconfigure all devices in the configuration file.
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.Sh FILES
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.Bl -tag -width /etc/vntab -compact
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.It Pa /etc/vntab
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default configuration file for
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.Fl a
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option
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.El
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.Sh EXAMPLES
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.Pp
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.Dl vnconfig vn0c /tmp/diskimage
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.Pp
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Configures the vnode disk
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.Pa vn0c .
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.Pp
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.Dl vnconfig -e vn0c /var/swapfile swap
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.Pp
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Configures
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.Pa vn0c
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and enables swapping on it.
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.Pp
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.Dl vnconfig -d vn0c myfilesystem mount=/mnt
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.Pp
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Unmounts (disables)
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.Pa vn0c .
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.Pp
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.Dl vnconfig -ae
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.Pp
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Configures and enables all devices specified in
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.Pa /etc/vntab .
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.Pp
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.Dl vnconfig -s labels -c vn0 somebackingfile
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.Dl disklabel -r -w vn0 auto
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.Dl disklabel -e vn0
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.Pp
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Is an example of how to configure a file-backed VN disk with a disk label
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and to initialize and then edit the label. Once you create the label, you
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can partition your VN disk and, for example, create a filesystem on one of
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the partitions. If you are using a file as backing store, it may be possible
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to recover your VN disk after a crash by vnconfig'ing the same file again
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and using the VN configuration already stored in the file rather then
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relabeling and recreating the filesystem. It is even possible to fsck the
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VN partitions that previously contained filesystems.
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.Pp
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.Dl vnconfig -e -s labels,reserve -S 400m vn1
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.Dl disklabel -r -w vn1 auto
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.Dl newfs /dev/vn1c
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.Dl mount /dev/vn1c /usr/obj
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.Pp
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Is an example of a swap-backed VN disk configuration. This example assumes
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that you have at least 400 megabytes of swap free (and hopefully much more).
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The swap space is pre-reserved in order to maintain maximum performance.
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We then label the disk, newfs it, and mount it as /usr/obj. Swap-backed VN
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devices are recoverable after a crash if you (A) use the reserve flag, and if
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(B) the same swap is reserved as was the last time, meaning that such
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vnconfig's would have to be run in your rc.local. In general, though, you
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only use swap-backed VN devices to hold information you don't mind losing
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on every reboot.
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.Sh SEE ALSO
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.Xr mount 2 ,
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.Xr swapon 2 ,
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.Xr unmount 2 ,
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.Xr vn 4
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