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1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
243 lines
7.6 KiB
Groff
243 lines
7.6 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" From: @(#)sysctl.8 8.1 (Berkeley) 6/6/93
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.\" $FreeBSD$
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.\"
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.Dd September 23, 1994
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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 bn
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.Ar name ...
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.Nm sysctl
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.Op Fl bn
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.Fl w
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.Ar name=value ...
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.Nm sysctl
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.Op Fl bn
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.Fl aAX
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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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.Pp
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The
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.Fl a
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flag can be used to list all the currently available string or integer values.
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.Pp
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The
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.Fl A
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flag will list all the known MIB names including opaques.
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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 the opaque values,
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information about the format and the length is printed in addition the first
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few bytes is dumped in hex.
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.Pp
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The
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.Fl X
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flag is the same as
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.Fl A
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except the entire value of opaque variables is hexdumped.
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.Pp
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The
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.Fl n
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flag 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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.Pp
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The
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.Fl b
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flag forces the value of the variable(s) to be output in raw, binary
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format. 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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.Pp
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If just a MIB style name is given,
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the corresponding value is retrieved.
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If a value is to be set, the
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.Fl w
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flag must be specified and the MIB name followed
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by an equal sign and the new value to be used.
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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 opaques.
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.Nm sysctl
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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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.Nm ps ,
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.Nm systat ,
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and
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.Nm netstat .
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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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.Bl -column net.inet.ip.forwardingxxxxxx 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 yes
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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.update integer yes
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.It kern.osreldate string no
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.It kern.bootfile string 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 machdep.console_device dev_t 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 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 EXAMPLES
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.Pp
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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 follow 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 follow 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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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 FILES
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.Bl -tag -width <netinet/icmpXvar.h> -compact
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.It Pa <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 Pa <sys/socket.h>
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definitions for second level network identifiers
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.It Pa <sys/gmon.h>
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definitions for third level profiling identifiers
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.It Pa <vm/vm_param.h>
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definitions for second level virtual memory identifiers
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.It Pa <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 Pa <netinet/icmp_var.h>
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definitions for fourth level ICMP identifiers
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.It Pa <netinet/udp_var.h>
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definitions for fourth level UDP identifiers
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.El
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.Sh SEE ALSO
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.Xr sysctl 3
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.Sh BUGS
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.Nm sysctl
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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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.Sh HISTORY
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.Nm sysctl
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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 sysctl
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was significantly remodeled.
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