538 lines
15 KiB
Groff
538 lines
15 KiB
Groff
.\" $NetBSD: sysctl.8,v 1.157 2006/12/04 08:59:13 pavel Exp $
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.\"
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.\" Copyright (c) 2004 The NetBSD Foundation, Inc.
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.\" 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 NetBSD
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.\" Foundation, Inc. and its contributors.
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.\" 4. Neither the name of The NetBSD Foundation nor the names of its
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.\" contributors may be used to endorse or promote products derived
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.\" from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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.\" POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\"
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.\" Copyright (c) 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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.\" @(#)sysctl.8 8.1 (Berkeley) 6/6/93
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.\"
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.Dd December 4, 2006
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.Dt SYSCTL 8
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.Os
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.Sh NAME
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.Nm sysctl
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.Nd get or set kernel state
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.Sh SYNOPSIS
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.Nm sysctl
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.Op Fl AdeMn
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.Oo
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.Fl r |
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.Fl x
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.Oc
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.Op Ar name ...
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.Nm sysctl
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.Op Fl nq
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.Oo
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.Fl r |
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.Fl x
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.Oc
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.Fl w
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.Ar name Ns Li = Ns Ar value ...
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.Nm sysctl
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.Op Fl en
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.Oo
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.Fl r |
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.Fl x
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.Oc
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.Fl a
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.Nm sysctl
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.Op Fl nq
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.Oo
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.Fl r |
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.Fl x
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.Oc
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.Fl f
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.Ar file
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.Sh DESCRIPTION
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The
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.Nm sysctl
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utility retrieves kernel state and allows processes with
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appropriate privilege to set kernel state.
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The state to be retrieved or set is described using a
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``Management Information Base'' (``MIB'') style name,
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described as a dotted set of components.
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The
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.Sq /
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character may also be used as a separator and a leading separator
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character is accepted.
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If
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.Ar name
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specifies a non-leaf node in the MIB, all the nodes underneath
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.Ar name
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will be printed.
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.Pp
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The following options are available:
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.Bl -tag -width indent
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.It Fl A
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List all the known MIB names including tables, unless any MIB
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arguments or
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.Fl f Ar file
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are given.
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Those with string or integer values will be printed as with the
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.Fl a
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flag; for table or structure values that
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.Nm
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is not able to print,
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the name of the utility to retrieve them is given.
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Errors in retrieving or setting values will be directed to stdout
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instead of stderr.
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.It Fl a
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List all the currently available string or integer values.
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The use of a solitary separator character (either
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.Sq \&.
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or
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.Sq / )
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by
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itself has the same effect.
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Any given
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.Ar name
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arguments are ignored if this option is specified.
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.It Fl d
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Descriptions of each of the nodes selected will be printed instead of
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their values.
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.It Fl e
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Separate the name and the value of the variable(s) with
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.Ql = .
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This is useful for producing output which can be fed back to the
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.Nm
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utility.
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This option is ignored if
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.Fl n
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is specified or a variable is being set.
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.It Fl f
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Specifies the name of a file to read and process.
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Blank lines and comments (beginning with
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.Ql # )
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are ignored.
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Line continuations with
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.Ql \e
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are permitted.
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Remaining lines are processed similarly to
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command line arguments of the form
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.Ar name
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or
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.Ar name Ns Li = Ns Ar value .
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The
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.Fl w
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flag is implied by
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.Fl f .
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Any
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.Ar name
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arguments are ignored.
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.It Fl M
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Makes
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.Nm
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print the MIB instead of any of the actual values contained in the
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MIB.
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This causes the entire MIB to be printed unless specific MIB arguments
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or
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.Fl f Ar file
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are also given.
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.It Fl n
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Specifies that the printing of the field name should be
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suppressed and that only its value should be output.
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This flag is useful for setting shell variables.
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For example, to save the pagesize in variable psize, use:
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.Bd -literal -offset indent -compact
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set psize=`sysctl -n hw.pagesize`
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.Ed
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.It Fl q
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Used to indicate that nothing should be printed for writes unless an
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error is detected.
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.It Fl r
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Raw output form.
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Values printed are in their raw binary forms as retrieved directly
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from the kernel.
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Some additional nodes that
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.Nm
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cannot print directly can be retrieved with this flag.
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This option conflicts with the
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.Fl x
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option.
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.It Fl w
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Sets the MIB style name given to the value given.
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The MIB style name and value must be separated by
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.Ql =
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with no whitespace.
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Only integral and string values can be set via this method.
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.It Fl x
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Makes
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.Nm
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print the requested value in a hexadecimal representation instead of
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its regular form.
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If specified more than once, the output for each value resembles that of
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.Xr hexdump 1
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when given the
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.Fl C
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flag.
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This option conflicts with the
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.Fl r
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option.
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.Pp
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.El
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The
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.Ql proc
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top-level MIB has a special semantic: it represent per-process values
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and as such may differ from one process to another.
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The second-level name is the pid of the process (in decimal form),
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or the special word
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.Ql curproc .
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For variables below
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.Ql proc. Ns Ao pid Ac Ns .rlimit ,
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the integer value may be replaced
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with the string
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.Ql unlimited
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if it matches the magic value used to disable
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a limit.
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.Pp
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The information available from
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.Nm sysctl
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consists of integers, strings, and tables.
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The tabular information can only be retrieved by special
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purpose programs such as
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.Nm ps ,
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.Nm systat ,
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and
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.Nm netstat .
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See
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.Xr sysctl 7
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for description of available MIBs.
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.Sh CREATION AND DELETION
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New nodes are allowed to be created by the superuser when the kernel
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is running at security level 0.
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These new nodes may refer to existing kernel data or to new data that
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is only instrumented by
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.Xr sysctl 3
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itself.
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.Pp
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The syntax for creating new nodes is
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.Dq //create=new.node.path
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followed by one or more of the following attributes separated by
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commas.
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The use of a double separator (both
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.Sq /
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and
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.Sq \&.
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can be used as
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separators) as the prefix tells sysctl that the first series of tokens
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is not a MIB name, but a command.
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It is recommended that the double separator preceding the command not
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be the same as the separator used in naming the MIB entry so as to
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avoid possible parse conflicts.
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The
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.Dq value
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assigned, if one is given, must be last.
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.Pp
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.Bl -bullet -compact
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.It
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.Ar type= Ns Aq Ar T
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where
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.Ar T
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must be one of
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.Dq node ,
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.Dq int ,
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.Dq string ,
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.Dq quad ,
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or
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.Dq struct .
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If the type is omitted, the
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.Dq node
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type is assumed.
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.It
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.Ar size= Ns Aq Ar S
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here,
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.Ar S
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asserts the size of the new node.
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Nodes of type
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.Dq node
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should not have a size set.
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The size may be omitted for nodes of types
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.Dq int
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or
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.Dq quad .
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If the size is omitted for a node of type
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.Dq string ,
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the size will be determined by the length of the given value, or by
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the kernel for kernel strings.
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Nodes of type
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.Dq struct
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must have their size explicitly set.
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.It
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.Ar addr= Ns Aq Ar A
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or
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.Ar symbol= Ns Aq Ar A
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The kernel address of the data being instrumented.
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If
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.Dq symbol
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is used, the symbol must be globally visible to the in-kernel
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.Xr ksyms 4
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driver.
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.It
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.Ar n= Ns Aq Ar N
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The MIB number to be assigned to the new node.
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If no number is specified, the kernel will assign a value.
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.It
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.Ar flags= Ns Aq Ar F
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A concatenated string of single letters that govern the behavior of
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the node.
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Flags currently available are:
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.Bl -tag -width www
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.It a
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Allow anyone to write to the node, if it is writable.
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.It h
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.Dq Hidden .
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.Nm
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must be invoked with
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.Fl A
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or the hidden node must be specifically requested in order to see it
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.It i
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.Dq Immediate .
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Makes the node store data in itself, rather than allocating new space
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for it.
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This is the default for nodes of type
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.Dq int
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and
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.Dq quad .
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This is the opposite of owning data.
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.It o
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.Dq Own .
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When the node is created, separate space will be allocated to store
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the data to be instrumented.
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This is the default for nodes of type
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.Dq string
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and
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.Dq struct
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where it is not possible to guarantee sufficient space to store the
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data in the node itself.
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.It p
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.Dq Private .
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Nodes that are marked private, and children of nodes so marked, are
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only viewable by the superuser.
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Be aware that the immediate data that some nodes may store is not
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necessarily protected by this.
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.It x
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.Dq Hexadecimal .
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Make
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.Nm
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default to hexadecimal display of the retrieved value
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.It r
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.Dq Read-only .
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The data instrumented by the given node is read-only.
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Note that other mechanisms may still exist for changing the data.
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This is the default for nodes that instrument data.
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.It w
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.Dq Writable .
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The data instrumented by the given node is writable at any time.
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This is the default for nodes that can have children.
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.It 1
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.Dq Read-only at securelevel 1 .
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The data instrumented by this node is writable until the securelevel
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reaches or passes securelevel 1.
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Examples of this include some network tunables.
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.It 2
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.Dq Read-only at securelevel 2 .
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The data instrumented by this node is writable until the securelevel
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reaches or passes securelevel 2.
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An example of this is the per-process core filename setting.
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.El
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.Pp
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.It
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.Ar value= Ns Aq Ar V
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An initial starting value for a new node that does not reference
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existing kernel data.
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Initial values can only be assigned for nodes of the
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.Dq int ,
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.Dq quad ,
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and
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.Dq string
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types.
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.El
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.Pp
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New nodes must fit the following set of criteria:
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.Pp
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.Bl -bullet -compact
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.It
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If the new node is to address an existing kernel object, only one of the
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.Dq symbol
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or
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.Dq addr
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arguments may be given.
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.It
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The size for a
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.Dq struct
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type node must be specified; no initial value is expected or permitted.
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.It
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Either the size or the initial value for a
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.Dq string
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node must be given.
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.It
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The node which will be the parent of the new node must be writable.
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.El
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.Pp
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If any of the given parameters describes an invalid configuration,
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.Nm
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will emit a diagnostic message to the standard error and exit.
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.Pp
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Descriptions can be added by the super-user to any node that does not
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have one, provided that the node is not marked with the
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.Dq PERMANENT
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flag.
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The syntax is similar to the syntax for creating new nodes with the
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exception of the keyword that follows the double separator at the
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start of the command:
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.Dq //describe=new.node.path=new node description .
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Once a description has been added, it cannot be changed or removed.
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.Pp
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When destroying nodes, only the path to the node is necessary, i.e.,
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.Dq //destroy=old.node.path .
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No other parameters are expected or permitted.
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Nodes being destroyed must have no children, and their parent must be
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writable.
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Nodes that are marked with the
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.Dq Dv PERMANENT
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flag (as assigned by the kernel) may not be deleted.
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.Pp
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In all cases, the initial
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.Sq =
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that follows the command (eg,
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.Dq create ,
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.Dq destroy ,
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or
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.Dq describe )
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may be replaced with another instance of the separator character,
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provided that the same separator character is used for the length of
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the name specification.
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.Sh FILES
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.Bl -tag -width /etc/sysctl.conf -compact
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.It Pa /etc/sysctl.conf
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.Nm
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variables set at boot time
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.El
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.Sh EXAMPLES
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For example, to retrieve the maximum number of processes allowed
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in the system, one would use the following request:
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.Bd -literal -offset indent -compact
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sysctl kern.maxproc
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.Ed
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.Pp
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To set the maximum number of processes allowed
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in the system to 1000, one would use the following request:
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.Bd -literal -offset indent -compact
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sysctl -w kern.maxproc=1000
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.Ed
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.Pp
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Information about the system clock rate may be obtained with:
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.Bd -literal -offset indent -compact
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sysctl kern.clockrate
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.Ed
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.Pp
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Information about the load average history may be obtained with:
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.Bd -literal -offset indent -compact
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sysctl vm.loadavg
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.Ed
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.Pp
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To view the values of the per-process variables of the current shell,
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the request:
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.Bd -literal -offset indent -compact
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sysctl proc.$$
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.Ed
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can be used if the shell interpreter replaces $$ with its pid (this is true
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for most shells).
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.Pp
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To redirect core dumps to the
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.Pa /var/tmp/ Ns Aq username
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directory,
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.Bd -literal -offset indent -compact
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sysctl -w proc.$$.corename=/var/tmp/%u/%n.core
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.Ed
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should be used.
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.Bd -literal -offset indent -compact
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sysctl -w proc.curproc.corename=/var/tmp/%u/%n.core
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.Ed
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changes the value for the sysctl process itself, and will not have the desired
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effect.
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.Pp
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|
To create the root of a new sub-tree called
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.Dq local
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add some children to the new node, and some descriptions:
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.Bd -literal -offset indent -compact
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sysctl -w //create=local
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sysctl -w //describe=local=my local sysctl tree
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sysctl -w //create=local.esm_debug,type=int,symbol=esm_debug,flags=w
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sysctl -w //describe=local.esm_debug=esm driver debug knob
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sysctl -w //create=local.audiodebug,type=int,symbol=audiodebug,flags=w
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sysctl -w //describe=local.audiodebug=generic audio debug knob
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.Ed
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Note that the children are made writable so that the two debug
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settings in question can be tuned arbitrarily.
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.Pp
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To destroy that same subtree:
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.Bd -literal -offset indent -compact
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sysctl -w //destroy=local.esm_debug
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sysctl -w //destroy=local.audiodebug
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sysctl -w //destroy=local
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.Ed
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.Sh SEE ALSO
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|
.Xr sysctl 3 ,
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.Xr ksyms 4 ,
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.Xr sysctl 7
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|
.Sh HISTORY
|
|
.Nm sysctl
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|
first appeared in
|
|
.Bx 4.4 .
|