path: root/system_cmds/sysctl.tproj/sysctl.8

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.\"	From: @(#)sysctl.8	8.1 (Berkeley) 6/6/93
.\" $FreeBSD$
.\"
.Dd January 17, 2011
.Dt SYSCTL 8
.Os
.Sh NAME
.Nm sysctl
.Nd get or set kernel state
.Sh SYNOPSIS
.Nm
.Op Fl bdehiNnoqx
.Ar name Ns Op = Ns Ar value
.Ar ...
.Nm
.Op Fl bdehNnoqx
.Fl a
.Sh DESCRIPTION
The
.Nm
utility retrieves kernel state and allows processes with appropriate
privilege to set kernel state.
The state to be retrieved or set is described using a
.Dq Management Information Base
.Pq Dq MIB
style name, described as a dotted set of
components.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl A
Equivalent to
.Fl o a
(for compatibility).
.It Fl a
List all the currently available non-opaque values.
This option is ignored if one or more variable names are specified on
the command line.
.It Fl b
Force the value of the variable(s) to be output in raw, binary format.
No names are printed and no terminating newlines are output.
This is mostly useful with a single variable.
.It Fl d
Print the description of the variable instead of its value.
.It Fl e
Separate the name and the value of the variable(s) with
.Ql = .
This is useful for producing output which can be fed back to the
.Nm
utility.
This option is ignored if either
.Fl N
or
.Fl n
is specified, or a variable is being set.
.It Fl h
Format output for human, rather than machine, readability.
.It Fl i
Ignore unknown OIDs.
The purpose is to make use of
.Nm
for collecting data from a variety of machines (not all of which
are necessarily running exactly the same software) easier.
.It Fl N
Show only variable names, not their values.
This is particularly useful with shells that offer programmable
completion.
To enable completion of variable names in
.Xr zsh 1 Pq Pa ports/shells/zsh ,
use the following code:
.Bd -literal -offset indent
listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
compctl -K listsysctls sysctl
.Ed
.Pp
To enable completion of variable names in
.Xr tcsh 1 ,
use:
.Pp
.Dl "complete sysctl 'n/*/`sysctl -Na`/'"
.It Fl n
Show only variable values, not their names.
This option is useful for setting shell variables.
For instance, to save the pagesize in variable
.Va psize ,
use:
.Pp
.Dl "set psize=`sysctl -n hw.pagesize`"
.It Fl o
Show opaque variables (which are normally suppressed).
The format and length are printed, as well as a hex dump of the first
sixteen bytes of the value.
.It Fl q
Suppress some warnings generated by
.Nm
to standard error.
.It Fl X
Equivalent to
.Fl x a
(for compatibility).
.It Fl x
As
.Fl o ,
but prints a hex dump of the entire value instead of just the first
few bytes.
.El
.Pp
The information available from
.Nm
consists of integers, strings, and opaque types.
The
.Nm
utility
only knows about a couple of opaque types, and will resort to hexdumps
for the rest.
The opaque information is much more useful if retrieved by special
purpose programs such as
.Xr ps 1 ,
.Xr systat 1 ,
and
.Xr netstat 1 .
.Pp
.\" Some of the variables which cannot be modified during normal system
.\" operation can be initialized via
.\" .Xr loader 8
.\" tunables.
.\" This can for example be done by setting them in
.\" .Xr loader.conf 5 .
.\" Please refer to
.\" .Xr loader.conf 5
.\" for more information on which tunables are available and how to set them.
.\" .Pp
The string and integer information is summarized below.
For a detailed description of these variable see
.Xr sysctl 3 .
.Pp
The changeable column indicates whether a process with appropriate
privilege can change the value.
String and integer values can be set using
.Nm .
.Bl -column xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx integerxxx
.It Sy "Name	Type	Changeable"
.It "hw.activecpu	integer	no"
.It "hw.busfrequency	integer	no"
.It "hw.busfrequency_max	integer	no"
.It "hw.busfrequency_min	integer	no"
.It "hw.byteorder	integer	no"
.It "hw.cacheconfig	struct	no"
.It "hw.cachelinesize	integer	no"
.It "hw.cachesize	struct	no"
.It "hw.cpu64bit_capable	integer	no"
.It "hw.cpufamily	integer	no"
.It "hw.cpufrequency	integer	no"
.It "hw.cpufrequency_max	integer	no"
.It "hw.cpufrequency_min	integer	no"
.It "hw.cpusubtype	integer	no"
.It "hw.cputhreadtype	integer	no"
.It "hw.cputype	integer	no"
.It "hw.l1dcachesize	integer	no"
.It "hw.l1icachesize	integer	no"
.It "hw.l2cachesize	integer	no"
.It "hw.l3cachesize	integer	no"
.It "hw.logicalcpu	integer	no"
.It "hw.logicalcpu_max	integer	no"
.It "hw.memsize	integer	no"
.It "hw.ncpu	integer	no"
.It "hw.packages	integer	no"
.It "hw.pagesize	integer	no"
.It "hw.physicalcpu	integer	no"
.It "hw.physicalcpu_max	integer	no"
.It "hw.tbfrequency	integer	no"
.It "kern.argmax	integer	no"
.It "kern.bootargs	string	no"
.It "kern.boottime	struct	no"
.It "kern.clockrate	struct	no"
.It "kern.coredump	integer	yes"
.It "kern.corefile	string	yes"
.It "kern.flush_cache_on_write	integer	yes"
.It "kern.hostid	integer	yes"
.It "kern.hostname	string	yes"
.It "kern.job_control	integer	no"
.It "kern.maxfiles	integer	yes"
.It "kern.maxfilesperproc	integer	yes"
.It "kern.maxnbuf	integer	yes"
.It "kern.maxproc	integer	yes"
.It "kern.maxprocperuid	integer	yes"
.It "kern.maxvnodes	integer	yes"
.It "kern.msgbuf	integer	yes"
.It "kern.nbuf	integer	no"
.It "kern.netboot	integer	no"
.It "kern.ngroups	integer	no"
.It "kern.nisdomainname	string	yes"
.It "kern.num_files	integer	no"
.It "kern.num_tasks	integer	no"
.It "kern.num_taskthreads	integer	no"
.It "kern.num_threads	integer	no"
.It "kern.num_vnodes	integer	no"
.It "kern.nx	integer	yes"
.It "kern.osrelease	string	no"
.It "kern.osrevision	integer	no"
.It "kern.ostype	string	no"
.It "kern.osversion	string	yes"
.It "kern.posix1version	integer	no"
.It "kern.procname	string	yes"
.It "kern.safeboot	integer	no"
.It "kern.saved_ids	integer	no"
.It "kern.secure_kernel	integer	no"
.It "kern.securelevel	integer	yes"
.It "kern.singleuser	integer	no"
.It "kern.sleeptime	struct	no"
.It "kern.slide	integer	no"
.It "kern.stack_depth_max	integer	no"
.It "kern.stack_size	integer	no"
.It "kern.sugid_coredump	integer	yes"
.It "kern.sugid_scripts	integer	yes"
.It "kern.symfile	string	no"
.It "kern.usrstack	integer	no"
.It "kern.usrstack64	integer	no"
.It "kern.uuid	string	no"
.It "kern.version	string	no"
.It "kern.waketime	struct	no"
.It "machdep.cpu.address_bits.physical	integer	no"
.It "machdep.cpu.address_bits.virtual	integer	no"
.It "machdep.cpu.brand	integer	no"
.It "machdep.cpu.brand_string	string	no"
.It "machdep.cpu.cache.L2_associativity	integer	no"
.It "machdep.cpu.cache.linesize	integer	no"
.It "machdep.cpu.cache.size	integer	no"
.It "machdep.cpu.core_count	integer	no"
.It "machdep.cpu.cores_per_package	integer	no"
.It "machdep.cpu.extfamily	integer	no"
.It "machdep.cpu.extfeature_bits	integer	no"
.It "machdep.cpu.extfeatures	string	no"
.It "machdep.cpu.extmodel	integer	no"
.It "machdep.cpu.family	integer	no"
.It "machdep.cpu.feature_bits	integer	no"
.It "machdep.cpu.features	string	no"
.It "machdep.cpu.leaf7_feature_bits	integer	no"
.It "machdep.cpu.leaf7_features	string	no"
.It "machdep.cpu.logical_per_package	integer	no"
.It "machdep.cpu.max_basic	integer	no"
.It "machdep.cpu.max_ext	integer	no"
.It "machdep.cpu.microcode_version	integer	no"
.It "machdep.cpu.model	integer	no"
.It "machdep.cpu.processor_flag	integer	no"
.It "machdep.cpu.signature	integer	no"
.It "machdep.cpu.stepping	integer	no"
.It "machdep.cpu.thread_count	integer	no"
.It "machdep.cpu.tlb.data.large	integer	no"
.It "machdep.cpu.tlb.data.large_level1	integer	no"
.It "machdep.cpu.tlb.data.small	integer	no"
.It "machdep.cpu.tlb.data.small_level1	integer	no"
.It "machdep.cpu.tlb.inst.large	integer	no"
.It "machdep.cpu.tlb.inst.small	integer	no"
.It "machdep.cpu.tlb.shared	integer	no"
.It "machdep.cpu.ucupdate	integer	yes"
.It "machdep.cpu.vendor	string	no"
.It "machdep.cpu.xsave.extended_state	integer	no"
.It "machdep.tsc.deep_idle_rebase	integer	yes"
.It "machdep.tsc.frequency	integer	no"
.It "machdep.tsc.nanotime.generation	integer	no"
.It "machdep.tsc.nanotime.shift	integer	no"
.It "net.inet.ip.forwarding	integer	yes"
.It "net.inet.ip.portrange.first	integer	yes"
.It "net.inet.ip.portrange.hifirst	integer	yes"
.It "net.inet.ip.portrange.hilast	integer	yes"
.It "net.inet.ip.portrange.last	integer	yes"
.It "net.inet.ip.portrange.lowfirst	integer	yes"
.It "net.inet.ip.portrange.lowlast	integer	yes"
.It "net.inet.ip.redirect	integer	yes"
.It "net.inet.ip.ttl	integer	yes"
.It "net.inet.udp.checksum	integer	yes"
.It "net.inet.udp.maxdgram	integer	yes"
.It "vm.loadavg	struct	no"
.It "vm.swapusage	struct	no"
.It "user.bc_base_max	integer	no"
.It "user.bc_dim_max	integer	no"
.It "user.bc_scale_max	integer	no"
.It "user.bc_string_max	integer	no"
.It "user.coll_weights_max	integer	no"
.It "user.cs_path	string	no"
.It "user.expr_nest_max	integer	no"
.It "user.line_max	integer	no"
.It "user.posix2_c_bind	integer	no"
.It "user.posix2_c_dev	integer	no"
.It "user.posix2_char_term	integer	no"
.It "user.posix2_fort_dev	integer	no"
.It "user.posix2_fort_run	integer	no"
.It "user.posix2_localedef	integer	no"
.It "user.posix2_sw_dev	integer	no"
.It "user.posix2_upe	integer	no"
.It "user.posix2_version	integer	no"
.It "user.re_dup_max	integer	no"
.It "user.stream_max	integer	no"
.It "user.tzname_max	integer	no"
.El
.Sh FILES
.Bl -tag -width ".In netinet/icmp_var.h" -compact
.It In sys/sysctl.h
definitions for top level identifiers, second level kernel and hardware
identifiers, and user level identifiers
.It In sys/socket.h
definitions for second level network identifiers
.It In sys/gmon.h
definitions for third level profiling identifiers
.It In vm/vm_param.h
definitions for second level virtual memory identifiers
.It In netinet/in.h
definitions for third level Internet identifiers and
fourth level IP identifiers
.It In netinet/icmp_var.h
definitions for fourth level ICMP identifiers
.It In netinet/udp_var.h
definitions for fourth level UDP identifiers
.El
.Sh EXAMPLES
For example, to retrieve the maximum number of processes allowed
in the system, one would use the following request:
.Pp
.Dl "sysctl kern.maxproc"
.Pp
To set the maximum number of processes allowed
per uid to 1000, one would use the following request:
.Pp
.Dl "sysctl kern.maxprocperuid=1000"
.Pp
Information about the system clock rate may be obtained with:
.Pp
.Dl "sysctl kern.clockrate"
.Pp
Information about the load average history may be obtained with:
.Pp
.Dl "sysctl vm.loadavg"
.Pp
More variables than these exist, and the best and likely only place
to search for their deeper meaning is undoubtedly the source where
they are defined.
.Sh COMPATIBILITY
The
.Fl w
option has been deprecated and is silently ignored.
.Sh SEE ALSO
.Xr sysctl 3 ,
.\" .Xr loader.conf 5 ,
.Xr sysctl.conf 5
.\" .Xr loader 8
.Sh HISTORY
A
.Nm
utility first appeared in
.Bx 4.4 .
.Pp
In
.Fx 2.2 ,
.Nm
was significantly remodeled.
.\" .Sh BUGS
.\" The
.\" .Nm
.\" utility presently exploits an undocumented interface to the kernel
.\" sysctl facility to traverse the sysctl tree and to retrieve format
.\" and name information.
.\" This correct interface is being thought about for the time being.