sysctl.8

.\"	$NetBSD: sysctl.8,v 1.79 2002/05/29 23:30:50 msaitoh Exp $
.\"
.\" Copyright (c) 1993
.\"	The Regents of the University of California.  All rights reserved.
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.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
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.\"    without specific prior written permission.
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"	@(#)sysctl.8	8.1 (Berkeley) 6/6/93
.\"
.Dd June 6, 1993
.Dt SYSCTL 8
.Os
.Sh NAME
.Nm sysctl
.Nd get or set kernel state
.Sh SYNOPSIS
.Nm sysctl
.Op Fl n
.Ar name ...
.Nm sysctl
.Op Fl n
.Op Fl q
.Fl w
.Ar name Ns Li = Ns Ar value ...
.Nm sysctl
.Op Fl n
.Fl a
.Nm sysctl
.Op Fl n
.Fl A
.Nm sysctl
.Op Fl n 
.Op Fl q
.Fl f
.Ar file
.Sh DESCRIPTION
The
.Nm sysctl
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
``Management Information Base'' (``MIB'') style name,
described as a dotted set of components.
The
.Fl a
flag can be used to list all the currently available string or integer values.
The
.Fl A
flag will list all the known MIB names including tables.
Those with string or integer values will be printed as with the
.Fl a
flag; for the table values,
the name of the utility to retrieve them is given.
.Pp
The
.Fl n
flag specifies that the printing of the field name should be
suppressed and that only its value should be output.
This flag is useful for setting shell variables.
For example, to save the pagesize in variable psize, use:
.Bd -literal -offset indent -compact
set psize=`sysctl -n hw.pagesize`
.Ed
.Pp
If just a MIB style name is given,
the corresponding value is retrieved.
If a value is to be set, the
.Fl w
flag must be specified and the MIB name followed
by an equal sign and the new value to be used.
.Pp
The
.Fl f
flag specifies the name of a file to read and process.  Blank lines and
comments (beginning with
.Ql # )
are ignored.  Line continuations with
.Ql \e
are permitted.  Remaining lines are processed similarly to
command line arguments of the form
.Ar name
or
.Ar name Ns Li = Ns Ar value .
The
.Fl w
flag is implied by
.Fl f .
.Pp
The 
.Fl q
flag may be used with 
.Fl f
and
.Fl w
to indicate that nothing should be printed for writes unless an error is
detected.
.Pp
The
.Ql proc
top-level MIB has a special semantic: it represent per-process values
and as such may differ from one process to another. The second-level name
is the pid of the process (in decimal form), or the special word
.Ql curproc .
For variables below
.Ql proc.\*[Lt]pid\*[Gt].rlimit ,
the integer value may be replaced
with the string
.Ql unlimited
if it matches the magic value used to disable
a limit.
.Pp
The information available from
.Nm sysctl
consists of integers, strings, and tables.
The tabular information can only be retrieved by special
purpose programs such as
.Nm ps ,
.Nm systat ,
and
.Nm netstat .
The string and integer information is summarized below.
For a detailed description of these variable see
.Xr sysctl 3 .
The changeable column indicates whether a process with appropriate
privilege can change the value.
.Bl -column proc.\*[Lt]pid\*[Gt].rlimit.coredumpsize.hardxxxxxx integerxxx
.It Sy Name	Type	Changeable
.It ddb.fromconsole	integer 	yes
.It ddb.lines	integer		yes
.It ddb.maxoff	integer 	yes
.It ddb.maxwidth	integer		yes
.It ddb.onpanic	integer		yes
.It ddb.radix	integer		yes
.It ddb.tabstops	integer		yes
.It hw.alignbytes	integer	no
.It hw.byteorder	integer	no
.It hw.disknames	string	no
.It hw.diskstats	struct	no
.It hw.machine	string	no
.It hw.machine_arch	string	no
.It hw.model	string	no
.It hw.ncpu	integer	no
.It hw.pagesize	integer	no
.It hw.physmem	integer	no
.It hw.usermem	integer	no
.It hw.cnmagic	string	yes
.It kern.argmax	integer	no
.It kern.autonicetime	integer	yes
.It kern.autoniceval	integer	yes
.It kern.boottime	struct	no
.It kern.chown_restricted	integer	no
.It kern.clockrate	struct	no
.It kern.defcorename	string	yes
.It kern.fsync	integer	no
.It kern.hostid	integer	yes
.It kern.hostname	string	yes
.It kern.iov_max	integer	no
.It kern.job_control	integer	no
.It kern.link_max	integer	no
.It kern.login_name_max	integer	no
.It kern.logsigexit	integer	yes
.It kern.max_canon	integer	no
.It kern.max_input	integer	no
.It kern.maxfiles	integer	yes
.It kern.maxpartitions	integer	no
.It kern.maxproc	integer	yes
.It kern.maxptys	integer	yes, special
.It kern.maxvnodes	integer	raise only
.It kern.mapped_files	integer	no
.It kern.memlock	integer	no
.It kern.memlock_rage	integer	no
.It kern.memory_protection	integer	no
.It kern.mbuf.mblowat	integer	yes
.It kern.mbuf.mcllowat	integer	yes
.It kern.mbuf.mclsize	integer	no
.It kern.mbuf.msize	integer	no
.It kern.mbuf.nmbclusters	integer	raise only
.It kern.msgbufsize	integer	no
.It kern.name_max	integer	no
.It kern.ngroups	integer	no
.It kern.no_trunc	integer	no
.It kern.osrelease	string	no
.It kern.osrevision	integer	no
.It kern.ostype	string	no
.It kern.path_max	integer	no
.It kern.pipe.maxkvasz	integer	yes
.It kern.pipe.maxloankvasz	integer	yes
.It kern.pipe.maxbigpipes	integer	yes
.It kern.pipe.nbigpipes	integer	no
.It kern.pipe.kvasize	integer	no
.It kern.posix1version	integer	no
.It kern.rawpartition	integer	no
.It kern.saved_ids	integer	no
.It kern.securelevel	integer	raise only
.It kern.synchronized_io	integer	no
.It kern.sysvmsg	integer	no
.It kern.sysvsem	integer	no
.It kern.sysvshm	integer	no
.It kern.tkstat.nin	quad	no
.It kern.tkstat.nout	quad	no
.It kern.tkstat.cancc	quad	no
.It kern.tkstat.rawcc	quad	no
.It kern.vdisable	integer	no
.It kern.version	string	no
.It machdep.console_device	dev_t	no
.It net.inet.icmp.maskrepl	integer	yes
.It net.inet.icmp.errppslimit	integer	yes
.It net.inet.icmp.rediraccept	integer	yes
.It net.inet.icmp.redirtimeout	integer	yes
.It net.inet.ip.allowsrcrt	integer	yes
.It net.inet.ip.anonportmax	integer	yes
.It net.inet.ip.anonportmin	integer	yes
.It net.inet.ip.directed-broadcast	integer		yes
.It net.inet.ip.forwarding	integer	yes
.It net.inet.ip.forwsrcrt	integer	yes
.It net.inet.ip.maxfragpacket	integer	yes
.It net.inet.ip.lowportmax	integer	yes
.It net.inet.ip.lowportmin	integer	yes
.It net.inet.ip.mtudisc	integer	yes
.It net.inet.ip.mtudisctimeout	integer	yes
.It net.inet.ip.redirect	integer	yes
.It net.inet.ip.subnetsarelocal	integer	yes
.It net.inet.ip.ttl	integer	yes
.It net.inet.ipsec.ah_cleartos	integer	yes
.It net.inet.ipsec.ah_net_deflev	integer	yes
.It net.inet.ipsec.ah_offsetmask	integer	yes
.It net.inet.ipsec.ah_trans_deflev	integer	yes
.It net.inet.ipsec.def_policy	integer	yes
.It net.inet.ipsec.dfbit	integer	yes
.It net.inet.ipsec.ecn	integer	yes
.It net.inet.ipsec.esp_net_deflev	integer	yes
.It net.inet.ipsec.esp_trans_deflev	integer	yes
.It net.inet.ipsec.inbound_call_ike	integer	yes
.It net.inet.tcp.ack_on_push	integer	yes
.It net.inet.tcp.compat_42	integer	yes
.It net.inet.tcp.cwm	integer	yes
.It net.inet.tcp.cwm_burstsize	integer	yes
.It net.inet.tcp.init_win	integer	yes
.It net.inet.tcp.keepcnt	integer	yes
.It net.inet.tcp.keepidle	integer	yes
.It net.inet.tcp.keepintvl	integer	yes
.It net.inet.tcp.log_refused	integer	yes
.It net.inet.tcp.mss_ifmtu	integer	yes
.It net.inet.tcp.mssdflt	integer	yes
.It net.inet.tcp.recvspace	integer	yes
.It net.inet.tcp.rfc1323	integer	yes
.It net.inet.tcp.rstppslimit	integer	yes
.It net.inet.tcp.sack	integer	yes
.It net.inet.tcp.sendspace	integer	yes
.It net.inet.tcp.slowhz	integer	no
.It net.inet.tcp.syn_bucket_limit	integer	yes
.It net.inet.tcp.syn_cache_interval	integer	yes
.It net.inet.tcp.syn_cache_limit	integer	yes
.It net.inet.tcp.timestamps	integer	yes
.It net.inet.tcp.win_scale	integer	yes
.It net.inet.udp.checksum	integer	yes
.It net.inet.udp.recvspace	integer	yes
.It net.inet.udp.sendspace	integer	yes
.It net.inet6.icmp6.errppslimit	integer	yes
.It net.inet6.icmp6.mtudisc_hiwat	integer	yes
.It net.inet6.icmp6.mtudisc_lowat	integer	yes
.It net.inet6.icmp6.nd6_debug	integer	yes
.It net.inet6.icmp6.nd6_delay	integer	yes
.It net.inet6.icmp6.nd6_maxnudhint	integer	yes
.It net.inet6.icmp6.nd6_mmaxtries	integer	yes
.It net.inet6.icmp6.nd6_prune	integer	yes
.It net.inet6.icmp6.nd6_umaxtries	integer	yes
.It net.inet6.icmp6.nd6_useloopback	integer	yes
.It net.inet6.icmp6.nodeinfo	integer	yes
.It net.inet6.icmp6.rediraccept	integer	yes
.It net.inet6.icmp6.redirtimeout	integer	yes
.It net.inet6.ip6.accept_rtadv	integer	yes
.It net.inet6.ip6.anonportmax	integer	yes
.It net.inet6.ip6.anonportmin	integer	yes
.It net.inet6.ip6.auto_flowlabel	integer	yes
.It net.inet6.ip6.v6only	integer	yes
.It net.inet6.ip6.dad_count	integer	yes
.It net.inet6.ip6.defmcasthlim	integer	yes
.It net.inet6.ip6.forwarding	integer	yes
.It net.inet6.ip6.gif_hlim	integer	yes
.It net.inet6.ip6.hdrnestlimit	integer	yes
.It net.inet6.ip6.hlim	integer	yes
.It net.inet6.ip6.kame_version	string	no
.It net.inet6.ip6.keepfaith	integer	yes
.It net.inet6.ip6.log_interval	integer	yes
.It net.inet6.ip6.lowportmax	integer	yes
.It net.inet6.ip6.lowportmin	integer	yes
.It net.inet6.ip6.maxfragpackets	integer	yes
.It net.inet6.ip6.maxfrags	integer	yes
.It net.inet6.ip6.redirect	integer	yes
.It net.inet6.ip6.rr_prune	integer	yes
.It net.inet6.ip6.use_deprecated	integer	yes
.It net.inet6.ipsec6.ah_net_deflev	integer	yes
.It net.inet6.ipsec6.ah_trans_deflev	integer	yes
.It net.inet6.ipsec6.def_policy	integer	yes
.It net.inet6.ipsec6.ecn	integer	yes
.It net.inet6.ipsec6.esp_net_deflev	integer	yes
.It net.inet6.ipsec6.esp_trans_deflev	integer	yes
.It net.inet6.ipsec6.inbound_call_ike	integer	yes
.It net.inet6.udp6.recvspace	integer	yes
.It net.inet6.udp6.sendspace	integer	yes
.It net.key.acq_exp_int	integer	yes
.It net.key.acq_maxtime	integer	yes
.It net.key.ah_keymin	integer	yes
.It net.key.debug	integer	yes
.It net.key.esp_auth	integer	yes
.It net.key.esp_keymin	integer	yes
.It net.key.kill_int	integer	yes
.It net.key.random_int	integer	yes
.It net.key.spi_max_value	integer	yes
.It net.key.spi_min_value	integer	yes
.It net.key.spi_try	integer	yes
.It proc.\*[Lt]pid\*[Gt].corename	string	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.coredumpsize.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.coredumpsize.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.cputime.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.cputime.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.datasize.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.datasize.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.filesize.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.filesize.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.maxproc.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.maxproc.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.memorylocked.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.memorylocked.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.memoryuse.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.memoryuse.soft	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.stacksize.hard	integer	yes
.It proc.\*[Lt]pid\*[Gt].rlimit.stacksize.soft	integer	yes
.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 vendor.\*[Lt]vendor\*[Gt].*	?	vendor specific
.It vfs.generic.usermount	integer	yes
.It vfs.nfs.iothreads	integer	yes
.It vm.anonmax	integer	yes
.It vm.anonmin	integer	yes
.It vm.execmax	integer	yes
.It vm.execmin	integer	yes
.It vm.filemax	integer	yes
.It vm.filemin	integer	yes
.It vm.loadavg	struct	no
.It vm.nkmempages	integer	no
.It vm.uvmexp	struct	no
.It vm.uvmexp2	struct	no
.It vm.vmmeter	struct	no
.El
.Pp
Entries found under
.Dq vendor.\*[Lt]vendor\*[Gt]
are left to be specified (and used) by vendors
using the
.Nx
operating system in their products.
Values and structure are vendor-defined, and no registry
exists right now.
.Sh FILES
.Bl -tag -width \*[Lt]netinet6/udp6Xvar.h\*[Gt] -compact
.It Pa \*[Lt]sys/sysctl.h\*[Gt]
definitions for top level identifiers, second level kernel and hardware
identifiers, and user level identifiers
.It Pa \*[Lt]sys/socket.h\*[Gt]
definitions for second level network identifiers
.It Pa \*[Lt]sys/gmon.h\*[Gt]
definitions for third level profiling identifiers
.It Pa \*[Lt]uvm/uvm_param.h\*[Gt]
definitions for second level virtual memory identifiers
.It Pa \*[Lt]netinet/in.h\*[Gt]
definitions for third level IPv4/v6 identifiers and
fourth level IPv4/v6 identifiers
.It Pa \*[Lt]netinet/icmp_var.h\*[Gt]
definitions for fourth level ICMP identifiers
.It Pa \*[Lt]netinet/icmp6.h\*[Gt]
definitions for fourth level ICMPv6 identifiers
.It Pa \*[Lt]netinet/tcp_var.h\*[Gt]
definitions for fourth level TCP identifiers
.It Pa \*[Lt]netinet/udp_var.h\*[Gt]
definitions for fourth level UDP identifiers
.It Pa \*[Lt]netinet6/udp6_var.h\*[Gt]
definitions for fourth level IPv6 UDP identifiers
.It Pa \*[Lt]netinet6/ipsec.h\*[Gt]
definitions for fourth level IPsec identifiers
.It Pa \*[Lt]netkey/key_var.h\*[Gt]
definitions for third level PF_KEY identifiers
.El
.Sh EXAMPLES
For example, to retrieve the maximum number of processes allowed
in the system, one would use the following request:
.Bd -literal -offset indent -compact
sysctl kern.maxproc
.Ed
.Pp
To set the maximum number of processes allowed
in the system to 1000, one would use the following request:
.Bd -literal -offset indent -compact
sysctl -w kern.maxproc=1000
.Ed
.Pp
Information about the system clock rate may be obtained with:
.Bd -literal -offset indent -compact
sysctl kern.clockrate
.Ed
.Pp
Information about the load average history may be obtained with:
.Bd -literal -offset indent -compact
sysctl vm.loadavg
.Ed
.Pp
To view the values of the per-process variables of the current shell,
the request:
.Bd -literal -offset indent -compact
sysctl proc.$$
.Ed
can be used if the shell interpreter replaces $$ with it's pid (this is true
for most shells).
.Pp
To redirect core dumps to the /var/tmp/\*[Lt]username\*[Gt] directory,
.Bd -literal -offset indent -compact
sysctl -w proc.$$.corename=/var/tmp/%u/%n.core
.Ed
Shall be used.
.Bd -literal -offset indent -compact
sysctl -w proc.curproc.corename=/var/tmp/%u/%n.core
.Ed
changes the value for the sysctl process itself, and will not have the desired
effect.
.Sh SEE ALSO
.Xr sysctl 3
.Sh HISTORY
.Nm sysctl
first appeared in
.Bx 4.4 .