330 lines
9.8 KiB
Groff
330 lines
9.8 KiB
Groff
.\" 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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.\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
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.\" $FreeBSD$
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.\"
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.Dd October 30, 2020
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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
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.Op Fl bdehiNnoTtqWx
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.Op Fl B Ar bufsize
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.Op Fl f Ar filename
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.Ar name Ns Op = Ns Ar value Ns Op , Ns Ar value
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.Ar ...
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.Nm
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.Op Fl bdehNnoTtqWx
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.Op Fl B Ar bufsize
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.Fl a
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.Sh DESCRIPTION
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The
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.Nm
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utility retrieves kernel state and allows processes with appropriate
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privilege to set kernel state.
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The state to be retrieved or set is described using a
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.Dq Management Information Base
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.Pq Dq MIB
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style name, described as a dotted set of
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components.
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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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Equivalent to
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.Fl o a
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(for compatibility).
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.It Fl a
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List all the currently available non-opaque values.
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This option is ignored if one or more variable names are specified on
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the command line.
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.It Fl b
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Force the value of the variable(s) to be output in raw, binary format.
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No names are printed and no terminating newlines are output.
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This is mostly useful with a single variable.
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.It Fl B Ar bufsize
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Set the buffer size to read from the
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.Nm
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to
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.Ar bufsize .
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This is necessary for a
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.Nm
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that has variable length, and the probe value of 0 is a valid length, such as
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.Va kern.arandom .
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.It Fl d
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Print the description of the variable instead of its value.
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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 either
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.Fl N
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or
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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 Ar filename
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Specify a file which contains a pair of name and value in each line.
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.Nm
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reads and processes the specified file first and then processes the name
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and value pairs in the command line argument.
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.It Fl h
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Format output for human, rather than machine, readability.
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.It Fl i
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Ignore unknown OIDs.
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The purpose is to make use of
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.Nm
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for collecting data from a variety of machines (not all of which
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are necessarily running exactly the same software) easier.
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.It Fl N
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Show only variable names, not their values.
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This is particularly useful with shells that offer programmable
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completion.
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To enable completion of variable names in
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.Xr zsh 1 Pq Pa ports/shells/zsh ,
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use the following code:
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.Bd -literal -offset indent
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listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
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compctl -K listsysctls sysctl
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.Ed
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.Pp
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To enable completion of variable names in
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.Xr tcsh 1 ,
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use:
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.Pp
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.Dl "complete sysctl 'n/*/`sysctl -Na`/'"
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.It Fl n
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Do not show variable names.
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This option is useful for setting shell variables.
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For instance, to save the pagesize in variable
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.Va psize ,
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use:
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.Pp
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.Dl "set psize=`sysctl -n hw.pagesize`"
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.It Fl o
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Show opaque variables (which are normally suppressed).
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The format and length are printed, as well as a hex dump of the first
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sixteen bytes of the value.
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.It Fl q
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Suppress some warnings generated by
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.Nm
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to standard error.
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.It Fl T
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Display only variables that are settable via loader (CTLFLAG_TUN).
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.It Fl t
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Print the type of the variable.
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.It Fl W
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Display only writable variables that are not statistical.
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Useful for determining the set of runtime tunable sysctls.
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.It Fl X
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Equivalent to
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.Fl x a
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(for compatibility).
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.It Fl x
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As
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.Fl o ,
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but prints a hex dump of the entire value instead of just the first
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few bytes.
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.El
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.Pp
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The information available from
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.Nm
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consists of integers, strings, and opaque types.
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The
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.Nm
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utility
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only knows about a couple of opaque types, and will resort to hexdumps
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for the rest.
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The opaque information is much more useful if retrieved by special
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purpose programs such as
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.Xr ps 1 ,
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.Xr systat 1 ,
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and
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.Xr netstat 1 .
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.Pp
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Some of the variables which cannot be modified during normal system
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operation can be initialized via
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.Xr loader 8
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tunables.
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This can for example be done by setting them in
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.Xr loader.conf 5 .
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Please refer to
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.Xr loader.conf 5
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for more information on which tunables are available and how to set them.
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.Pp
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The string and integer information is summarized below.
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For a detailed description of these variable see
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.Xr sysctl 3 .
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.Pp
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The changeable column indicates whether a process with appropriate
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privilege can change the value.
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String and integer values can be set using
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.Nm .
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.Bl -column security.bsd.unprivileged_read_msgbuf integerxxx
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.It Sy "Name Type Changeable"
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.It "kern.ostype string no"
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.It "kern.osrelease string no"
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.It "kern.osrevision integer no"
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.It "kern.version string no"
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.It "kern.maxvnodes integer yes"
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.It "kern.maxproc integer no"
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.It "kern.maxprocperuid integer yes"
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.It "kern.maxfiles integer yes"
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.It "kern.maxfilesperproc integer yes"
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.It "kern.argmax integer no"
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.It "kern.securelevel integer raise only"
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.It "kern.hostname string yes"
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.It "kern.hostid integer yes"
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.It "kern.clockrate struct no"
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.It "kern.posix1version integer no"
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.It "kern.ngroups integer no"
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.It "kern.job_control integer no"
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.It "kern.saved_ids integer no"
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.It "kern.boottime struct no"
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.It "kern.domainname string yes"
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.It "kern.filedelay integer yes"
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.It "kern.dirdelay integer yes"
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.It "kern.metadelay integer yes"
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.It "kern.osreldate integer no"
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.It "kern.bootfile string yes"
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.It "kern.corefile string yes"
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.It "kern.logsigexit integer yes"
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.It "security.bsd.suser_enabled integer yes"
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.It "security.bsd.see_other_uids integer yes"
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.It "security.bsd.unprivileged_proc_debug integer yes"
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.It "security.bsd.unprivileged_read_msgbuf integer yes"
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.It "vm.loadavg struct no"
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.It "hw.machine string no"
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.It "hw.model string no"
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.It "hw.ncpu integer no"
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.It "hw.byteorder integer no"
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.It "hw.physmem integer no"
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.It "hw.usermem integer no"
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.It "hw.pagesize integer no"
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.It "hw.floatingpoint integer no"
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.It "hw.machine_arch string no"
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.It "hw.realmem integer no"
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.It "machdep.adjkerntz integer yes"
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.It "machdep.disable_rtc_set integer yes"
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.It "machdep.guessed_bootdev string no"
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.It "user.cs_path string no"
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.It "user.bc_base_max integer no"
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.It "user.bc_dim_max integer no"
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.It "user.bc_scale_max integer no"
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.It "user.bc_string_max integer no"
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.It "user.coll_weights_max integer no"
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.It "user.expr_nest_max integer no"
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.It "user.line_max integer no"
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.It "user.re_dup_max integer no"
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.It "user.posix2_version integer no"
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.It "user.posix2_c_bind integer no"
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.It "user.posix2_c_dev integer no"
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.It "user.posix2_char_term integer no"
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.It "user.posix2_fort_dev integer no"
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.It "user.posix2_fort_run integer no"
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.It "user.posix2_localedef integer no"
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.It "user.posix2_sw_dev integer no"
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.It "user.posix2_upe integer no"
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.It "user.stream_max integer no"
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.It "user.tzname_max integer no"
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.It "user.localbase string no"
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.El
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.Sh FILES
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.Bl -tag -width ".In netinet/icmp_var.h" -compact
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.It In sys/sysctl.h
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definitions for top level identifiers, second level kernel and hardware
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identifiers, and user level identifiers
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.It In sys/socket.h
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definitions for second level network identifiers
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.It In sys/gmon.h
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definitions for third level profiling identifiers
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.It In vm/vm_param.h
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definitions for second level virtual memory identifiers
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.It In netinet/in.h
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definitions for third level Internet identifiers and
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fourth level IP identifiers
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.It In netinet/icmp_var.h
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definitions for fourth level ICMP identifiers
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.It In netinet/udp_var.h
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definitions for fourth level UDP identifiers
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.El
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.Sh EXIT STATUS
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.Ex -std
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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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.Pp
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.Dl "sysctl kern.maxproc"
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.Pp
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To set the maximum number of processes allowed
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per uid to 1000, one would use the following request:
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.Pp
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.Dl "sysctl kern.maxprocperuid=1000"
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.Pp
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Information about the system clock rate may be obtained with:
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.Pp
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.Dl "sysctl kern.clockrate"
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.Pp
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Information about the load average history may be obtained with:
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.Pp
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.Dl "sysctl vm.loadavg"
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.Pp
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More variables than these exist, and the best and likely only place
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to search for their deeper meaning is undoubtedly the source where
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they are defined.
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.Sh COMPATIBILITY
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The
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.Fl w
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option has been deprecated and is silently ignored.
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.Sh SEE ALSO
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.Xr sysctl 3 ,
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.Xr loader.conf 5 ,
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.Xr sysctl.conf 5 ,
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.Xr loader 8
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.Sh HISTORY
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A
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.Nm
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utility first appeared in
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.Bx 4.4 .
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.Pp
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In
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.Fx 2.2 ,
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.Nm
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was significantly remodeled.
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.Sh BUGS
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The
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.Nm
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utility presently exploits an undocumented interface to the kernel
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sysctl facility to traverse the sysctl tree and to retrieve format
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and name information.
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This correct interface is being thought about for the time being.
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