.\" Copyright (c) 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by the University of .\" California, Berkeley and its contributors. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)sysctl.8 8.2 (Berkeley) 5/9/95 .\" .Dd "May 9, 1995" .Dt SYSCTL 8 .Os .Sh NAME .Nm sysctl .Nd get or set kernel state .Sh SYNOPSIS .Nm sysctl .Op Fl bn .Ar name ... .Nm sysctl .Op Fl bn .Fl w .Ar name=value ... .Nm sysctl .Op Fl bn .Fl a .Nm sysctl .Op Fl bn .Fl A .Nm sysctl .Op Fl bn .Fl X .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. .Pp The following options are available: .Bl -tag -width indent .\" ========== .It Fl A List all MIB variables including 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 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 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 w Ar name=value Used to set values. The MIB name ( .Ar name ) followed by an equal sign and the new value ( .Ar value ) to be used. .\" ========== .It Fl X Same as .Fl A , but prints a hex dump of the entire value instead of just the first few bytes. .El .Pp If just a MIB style name is given, the corresponding value is retrieved. .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 net.inet.ip.forwardingxxxxxx integerxxx .It Sy Name Type Changeable .It kern.ostype string no .It kern.osrelease string no .It kern.osrevision integer no .It kern.version string no .It kern.maxvnodes integer yes .It kern.maxproc integer yes .It kern.maxfiles integer yes .It kern.argmax integer no .It kern.securelevel integer raise only .It kern.hostname string yes .It kern.hostid integer yes .It kern.clockrate struct no .It kern.posix1version integer no .It kern.ngroups integer no .It kern.job_control integer no .It kern.saved_ids integer no .It kern.link_max integer no .It kern.max_canon integer no .It kern.max_input integer no .It kern.name_max integer no .It kern.path_max integer no .It kern.pipe_buf integer no .It kern.chown_restricted integer no .It kern.no_trunc integer no .It kern.vdisable integer no .It kern.boottime struct no .It vm.loadavg struct no .It vm.swapusage struct no .It machdep.console_device dev_t no .It net.inet.ip.forwarding integer yes .It net.inet.ip.redirect integer yes .It net.inet.ip.ttl integer yes .It net.inet.icmp.maskrepl integer yes .It net.inet.udp.checksum integer yes .It hw.machine string no .It hw.model string no .It hw.ncpu integer no .It hw.byteorder integer no .It hw.physmem integer no .It hw.usermem integer no .It hw.memsize integer no .It hw.pagesize integer no .It user.cs_path string 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.expr_nest_max integer no .It user.line_max integer no .It user.re_dup_max integer no .It user.posix2_version 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 .El .Pp The .Nm sysctl program can get or set debugging variables that have been identified for its display. This information can be obtained by using the command: .Bd -literal -offset indent sysctl debug .Ed .Pp In addition, .Nm sysctl can extract information about the filesystems that have been compiled into the running system. This information can be obtained by using the command: .Bd -literal -offset indent sysctl vfs .Ed .Pp By default, only filesystems that are actively being used are listed. Use of the .Fl A flag lists all the filesystems compiled into the running kernel. .Sh EXAMPLES .Pp For example, to retrieve the maximum number of processes allowed in the system, one would use the request: .Bd -literal -offset indent sysctl kern.maxproc .Ed .Pp To set the maximum number of processes allowed in the system to 1000, one would use the request: .Bd -literal -offset inden sysctl -w kern.maxproc=1000 .Ed .Pp Information about the system clock rate may be obtained with: .Bd -literal -offset indent sysctl kern.clockrate .Ed .Pp Information about the load average history may be obtained with: .Bd -literal -offset indent sysctl vm.loadavg .Ed .Pp Information about the system's swap space usage may be obtained with: .Bd -literal -offset indent sysctl vm.swapusage .Ed .Sh FILES .Bl -tag -width -compact .It Pa definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers .It Pa definitions for second level network identifiers .It Pa definitions for third level profiling identifiers .It Pa definitions for second level virtual memory identifiers .It Pa definitions for third level Internet identifiers and fourth level IP identifiers .It Pa definitions for fourth level ICMP identifiers .It Pa definitions for fourth level UDP identifiers .El .Sh SEE ALSO .Xr sysctl 3 .Sh HISTORY .Nm sysctl first appeared in 4.4BSD.