242 lines
7.6 KiB
Groff
242 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
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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 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 currently available string or integer values.
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.It Fl A
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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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.It Fl X
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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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.It Fl n
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Specify 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 b
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Force 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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.It Fl w Ar name=value ...
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Set the MIB
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.Ar name
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to the new
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.Ar value .
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If just a MIB style
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.Ar name
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is given,
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the corresponding value is retrieved.
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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 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 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.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 kern.corefile string yes
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.It kern.logsigexit 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 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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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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per uid to 1000, one would use the follow request:
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.Bd -literal -offset indent -compact
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sysctl -w kern.maxprocperuid=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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.Xr blackhole 4
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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
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was significantly remodeled.
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