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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
q Dq MIB style name, described as a dotted set of components.
p The following options are available: l -tag -width indent t Fl A Equivalent to .Fl o a (for compatibility). t 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. t 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. t Fl d Print the description of the variable instead of its value. t 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. t Fl h Format output for human, rather than machine, readability. t 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. t 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: d -literal -offset indent listsysctls () { set -A reply $(sysctl -AN ${1%.*}) } compctl -K listsysctls sysctl .Ed
p To enable completion of variable names in .Xr tcsh 1 , use:
p .Dl "complete sysctl 'n/*/`sysctl -Na`/'" t 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:
p .Dl "set psize=`sysctl -n hw.pagesize`" t 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. t Fl q Suppress some warnings generated by .Nm to standard error. t Fl X Equivalent to .Fl x a (for compatibility). t Fl x As .Fl o , but prints a hex dump of the entire value instead of just the first few bytes. .El
p 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 .
p
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 .
p The changeable column indicates whether a process with appropriate privilege can change the value. String and integer values can be set using .Nm . l -column xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx integerxxx t Sy "Name Type Changeable" t "hw.activecpu integer no" t "hw.busfrequency integer no" t "hw.busfrequency_max integer no" t "hw.busfrequency_min integer no" t "hw.byteorder integer no" t "hw.cacheconfig struct no" t "hw.cachelinesize integer no" t "hw.cachesize struct no" t "hw.cpu64bit_capable integer no" t "hw.cpufamily integer no" t "hw.cpufrequency integer no" t "hw.cpufrequency_max integer no" t "hw.cpufrequency_min integer no" t "hw.cpusubtype integer no" t "hw.cputhreadtype integer no" t "hw.cputype integer no" t "hw.l1dcachesize integer no" t "hw.l1icachesize integer no" t "hw.l2cachesize integer no" t "hw.l3cachesize integer no" t "hw.logicalcpu integer no" t "hw.logicalcpu_max integer no" t "hw.memsize integer no" t "hw.ncpu integer no" t "hw.packages integer no" t "hw.pagesize integer no" t "hw.physicalcpu integer no" t "hw.physicalcpu_max integer no" t "hw.tbfrequency integer no" t "kern.argmax integer no" t "kern.bootargs string no" t "kern.boottime struct no" t "kern.clockrate struct no" t "kern.coredump integer yes" t "kern.corefile string yes" t "kern.flush_cache_on_write integer yes" t "kern.hostid integer yes" t "kern.hostname string yes" t "kern.job_control integer no" t "kern.maxfiles integer yes" t "kern.maxfilesperproc integer yes" t "kern.maxnbuf integer yes" t "kern.maxproc integer yes" t "kern.maxprocperuid integer yes" t "kern.maxvnodes integer yes" t "kern.msgbuf integer yes" t "kern.nbuf integer no" t "kern.netboot integer no" t "kern.ngroups integer no" t "kern.nisdomainname string yes" t "kern.num_files integer no" t "kern.num_tasks integer no" t "kern.num_taskthreads integer no" t "kern.num_threads integer no" t "kern.num_vnodes integer no" t "kern.nx integer yes" t "kern.osrelease string no" t "kern.osrevision integer no" t "kern.ostype string no" t "kern.osversion string yes" t "kern.posix1version integer no" t "kern.procname string yes" t "kern.safeboot integer no" t "kern.saved_ids integer no" t "kern.secure_kernel integer no" t "kern.securelevel integer yes" t "kern.singleuser integer no" t "kern.sleeptime struct no" t "kern.slide integer no" t "kern.stack_depth_max integer no" t "kern.stack_size integer no" t "kern.sugid_coredump integer yes" t "kern.sugid_scripts integer yes" t "kern.symfile string no" t "kern.usrstack integer no" t "kern.usrstack64 integer no" t "kern.uuid string no" t "kern.version string no" t "kern.waketime struct no" t "machdep.cpu.address_bits.physical integer no" t "machdep.cpu.address_bits.virtual integer no" t "machdep.cpu.brand integer no" t "machdep.cpu.brand_string string no" t "machdep.cpu.cache.L2_associativity integer no" t "machdep.cpu.cache.linesize integer no" t "machdep.cpu.cache.size integer no" t "machdep.cpu.core_count integer no" t "machdep.cpu.cores_per_package integer no" t "machdep.cpu.extfamily integer no" t "machdep.cpu.extfeature_bits integer no" t "machdep.cpu.extfeatures string no" t "machdep.cpu.extmodel integer no" t "machdep.cpu.family integer no" t "machdep.cpu.feature_bits integer no" t "machdep.cpu.features string no" t "machdep.cpu.leaf7_feature_bits integer no" t "machdep.cpu.leaf7_features string no" t "machdep.cpu.logical_per_package integer no" t "machdep.cpu.max_basic integer no" t "machdep.cpu.max_ext integer no" t "machdep.cpu.microcode_version integer no" t "machdep.cpu.model integer no" t "machdep.cpu.processor_flag integer no" t "machdep.cpu.signature integer no" t "machdep.cpu.stepping integer no" t "machdep.cpu.thread_count integer no" t "machdep.cpu.tlb.data.large integer no" t "machdep.cpu.tlb.data.large_level1 integer no" t "machdep.cpu.tlb.data.small integer no" t "machdep.cpu.tlb.data.small_level1 integer no" t "machdep.cpu.tlb.inst.large integer no" t "machdep.cpu.tlb.inst.small integer no" t "machdep.cpu.tlb.shared integer no" t "machdep.cpu.ucupdate integer yes" t "machdep.cpu.vendor string no" t "machdep.cpu.xsave.extended_state integer no" t "machdep.tsc.deep_idle_rebase integer yes" t "machdep.tsc.frequency integer no" t "machdep.tsc.nanotime.generation integer no" t "machdep.tsc.nanotime.shift integer no" t "net.inet.ip.forwarding integer yes" t "net.inet.ip.portrange.first integer yes" t "net.inet.ip.portrange.hifirst integer yes" t "net.inet.ip.portrange.hilast integer yes" t "net.inet.ip.portrange.last integer yes" t "net.inet.ip.portrange.lowfirst integer yes" t "net.inet.ip.portrange.lowlast integer yes" t "net.inet.ip.redirect integer yes" t "net.inet.ip.ttl integer yes" t "net.inet.udp.checksum integer yes" t "net.inet.udp.maxdgram integer yes" t "vm.loadavg struct no" t "vm.swapusage struct no" t "user.bc_base_max integer no" t "user.bc_dim_max integer no" t "user.bc_scale_max integer no" t "user.bc_string_max integer no" t "user.coll_weights_max integer no" t "user.cs_path string no" t "user.expr_nest_max integer no" t "user.line_max integer no" t "user.posix2_c_bind integer no" t "user.posix2_c_dev integer no" t "user.posix2_char_term integer no" t "user.posix2_fort_dev integer no" t "user.posix2_fort_run integer no" t "user.posix2_localedef integer no" t "user.posix2_sw_dev integer no" t "user.posix2_upe integer no" t "user.posix2_version integer no" t "user.re_dup_max integer no" t "user.stream_max integer no" t "user.tzname_max integer no" .El .Sh FILES l -tag -width ".In netinet/icmp_var.h" -compact t In sys/sysctl.h definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers t In sys/socket.h definitions for second level network identifiers t In sys/gmon.h definitions for third level profiling identifiers t In vm/vm_param.h definitions for second level virtual memory identifiers t In netinet/in.h definitions for third level Internet identifiers and fourth level IP identifiers t In netinet/icmp_var.h definitions for fourth level ICMP identifiers t 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:
p .Dl "sysctl kern.maxproc"
p To set the maximum number of processes allowed per uid to 1000, one would use the following request:
p .Dl "sysctl kern.maxprocperuid=1000"
p Information about the system clock rate may be obtained with:
p .Dl "sysctl kern.clockrate"
p Information about the load average history may be obtained with:
p .Dl "sysctl vm.loadavg"
p
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
x 4.4 .
p
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.