[-bdehNnoqx
]
name [= value
]
...
[-bdehNnoqx
]
-a
DESCRIPTION
The
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 following options are available:
-A
Equivalent to
-o a
(for compatibility).
-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.
-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.
-d
Print the description of the variable instead of its value.
-e
Separate the name and the value of the variable(s) with
`='
This is useful for producing output which can be fed back to the
utility.
This option is ignored if either
-N
or
-n
is specified, or a variable is being set.
-h
Format output for human, rather than machine, readability.
-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
zsh(1)PqPaports/shells/zsh,
use the following code:
listsysctls () { set -A reply $(sysctl -AN ${1%.*}) }
compctl -K listsysctls sysctl
To enable completion of variable names in
tcsh(1),
use:
"complete sysctl 'n/*/`sysctl -Na`/'"
-n
Show only variable values, not their names.
This option is useful for setting shell variables.
For instance, to save the pagesize in variable
psize
use:
"set psize=`sysctl -n hw.pagesize`"
-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.
-q
Suppress some warnings generated by
to standard error.
-X
Equivalent to
-x a
(for compatibility).
-x
As
-o
but prints a hex dump of the entire value instead of just the first
few bytes.
The information available from
consists of integers, strings, devices
(Vt dev_t
)
and opaque types.
The
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
ps(1),
systat(1),
and
netstat(1).
Some of the variables which cannot be modified during normal system
operation can be initialized via
loader(8)
tunables.
This can for example be done by setting them in
loader.conf5.
Please refer to
loader.conf5
for more information on which tunables are available and how to set them.
The string and integer information is summarized below.
For a detailed description of these variable see
sysctl(3).
The changeable column indicates whether a process with appropriate
privilege can change the value.
String, integer, and devices values can be set using
.
For device values,
value
can be specified as a character device special file name.
Special values
off
and
none
denote
``no device''
NameTypeChangeable
"kern.ostypestringno
"kern.osreleasestringno
"kern.osrevisionintegerno
"kern.versionstringno
"kern.maxvnodesintegeryes
"kern.maxprocintegerno
"kern.maxprocperuidintegeryes
"kern.maxfilesintegeryes
"kern.maxfilesperprocintegeryes
"kern.argmaxintegerno
"kern.securelevelintegerraise only
"kern.hostnamestringyes
"kern.hostidintegeryes
"kern.clockratestructno
"kern.posix1versionintegerno
"kern.ngroupsintegerno
"kern.job_controlintegerno
"kern.saved_idsintegerno
"kern.boottimestructno
"kern.domainnamestringyes
"kern.filedelayintegeryes
"kern.dirdelayintegeryes
"kern.metadelayintegeryes
"kern.osreldatestringno
"kern.bootfilestringyes
"kern.corefilestringyes
"kern.logsigexitintegeryes
"security.bsd.suser_enabledintegeryes
"security.bsd.see_other_uidsintegeryes
"security.bsd.unprivileged_proc_debugintegeryes
"security.bsd.unprivileged_read_msgbufintegeryes
"vm.loadavgstructno
"hw.machinestringno
"hw.modelstringno
"hw.ncpuintegerno
"hw.byteorderintegerno
"hw.physmemintegerno
"hw.usermemintegerno
"hw.pagesizeintegerno
"hw.floatingpointintegerno
"hw.machine_archstringno
"hw.realmemintegerno
"machdep.console_devicedev_tno
"machdep.adjkerntzintegeryes
"machdep.disable_rtc_setintegeryes
"machdep.guessed_bootdevstringno
"user.cs_pathstringno
"user.bc_base_maxintegerno
"user.bc_dim_maxintegerno
"user.bc_scale_maxintegerno
"user.bc_string_maxintegerno
"user.coll_weights_maxintegerno
"user.expr_nest_maxintegerno
"user.line_maxintegerno
"user.re_dup_maxintegerno
"user.posix2_versionintegerno
"user.posix2_c_bindintegerno
"user.posix2_c_devintegerno
"user.posix2_char_termintegerno
"user.posix2_fort_devintegerno
"user.posix2_fort_runintegerno
"user.posix2_localedefintegerno
"user.posix2_sw_devintegerno
"user.posix2_upeintegerno
"user.stream_maxintegerno
"user.tzname_maxintegerno
FILES
In sys/sysctl.h
definitions for top level identifiers, second level kernel and hardware
identifiers, and user level identifiers
In sys/socket.h
definitions for second level network identifiers
In sys/gmon.h
definitions for third level profiling identifiers
In vm/vm_param.h
definitions for second level virtual memory identifiers
In netinet/in.h
definitions for third level Internet identifiers and
fourth level IP identifiers
In netinet/icmp_var.h
definitions for fourth level ICMP identifiers
In netinet/udp_var.h
definitions for fourth level UDP identifiers
EXAMPLES
For example, to retrieve the maximum number of processes allowed
in the system, one would use the following request:
"sysctl kern.maxproc"
To set the maximum number of processes allowed
per uid to 1000, one would use the following request:
"sysctl kern.maxprocperuid=1000"
Information about the system clock rate may be obtained with:
"sysctl kern.clockrate"
Information about the load average history may be obtained with:
"sysctl vm.loadavg"
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.
COMPATIBILITY
The
-w
option has been deprecated and is silently ignored.
The
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.
