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2365fe5616
Most sysctl nodes only return a single value, but some nodes return an array of values (e.g. kern.cp_time). sysctl(8) understand how to display the values of a node that returns multiple values (it prints out each numeric value separated by spaces). However, until now sysctl(8) has only been able to set sysctl nodes to a single value. This change allows sysctl to accept a new value for a numeric sysctl node that contains multiple values separated by either spaces or commas. sysctl(8) parses this list into an array of values and passes the array as the "new" value to sysctl(2). Reviewed by: rpokala MFC after: 1 week Sponsored by: Chelsio Communications Differential Revision: https://reviews.freebsd.org/D14569
327 lines
9.7 KiB
Groff
327 lines
9.7 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 March 9, 2018
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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 bdehiNnoRTtqx
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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 bdehNnoRTtqx
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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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Show only variable values, not their 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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.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 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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