sysctl(1M)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXTENDED DESCRIPTION | EXAMPLES | FILES | ATTRIBUTES | SEE ALSO | BUGS

NAME

sysctl- get or set kernel state

SYNOPSIS

sysctl [-bn] name...
sysctl [-bn] -w name=value...
sysctl [-bn] -AaX

DESCRIPTION

>sysctl is a target utility.

sysctl retrieves the kernel state and allows processes with appropriate privilege to set the 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.

OPTIONS

sysctl takes the following options:

-A

List all the known MIB names including opaques. Those with string or integer values are printed as with the -a option. For opaque values, information about the format and the length is printed in addition to the first few bytes, which are dumped in hexadecimal form.

-a

List all the currently available string or integer values.

-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.

-n

Specify 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 page size in variable psize, use:

set psize=`sysctl -n hw.pagesize`

-w name=value

Set the MIB name to the new value. If just a MIB style name is given, the corresponding value is retrieved.

-X

Same as -A except the entire value of opaque variables is dumped in hexadecimal form.

EXTENDED DESCRIPTION

The information available using sysctl consists of integers, strings, and opaques. sysctl 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, systat, and netstat.

The string and integer information is summarized below. The changeable column indicates whether a process with appropriate privileges can change the value.

Name	Type	Changeable
kern.ostype	string	no
kern.osrelease	string	no
kern.osrevision	integer	no
kern.version	string	no
kern.maxvnodes	integer	yes
kern.maxproc	integer	yes
kern.maxprocperuid	integer	yes
kern.maxfiles	integer	yes
kern.maxfilesperproc	integer	yes
kern.argmax	integer	no
kern.securelevel	integer	raise only
kern.hostname	string	yes
kern.hostid	integer	yes
kern.clockrate	struct	no
kern.posix1version	integer	no
kern.ngroups	integer	no
kern.job_control	integer	no
kern.saved_ids	integer	no
kern.boottime	struct	no
kern.domainname	string	yes
kern.update	integer	yes
kern.osreldate	string	no
kern.bootfile	string	yes
vm.loadavg	struct	no
hw.machine	string	no
hw.model	string	no
hw.ncpu	integer	no
hw.byteorder	integer	no
hw.physmem	integer	no
hw.usermem	integer	no
hw.pagesize	integer	no
hw.floatingpoint	integer	no
hw.machine_arch	string	no
machdep.console_device	dev_t	no
machdep.adjkerntz	integer	yes
machdep.disable_rtc_set	integer	yes
user.cs_path	string	no
user.bc_base_max	integer	no
user.bc_dim_max	integer	no
user.bc_scale_max	integer	no
user.bc_string_max	integer	no
user.coll_weights_max	integer	no
user.expr_nest_max	integer	no
user.line_max	integer	no
user.re_dup_max	integer	no
user.posix2_version	integer	no
user.posix2_c_bind	integer	no
user.posix2_c_dev	integer	no
user.posix2_char_term	integer	no
user.posix2_fort_dev	integer	no
user.posix2_fort_run	integer	no
user.posix2_localedef	integer	no
user.posix2_sw_dev	integer	no
user.posix2_upe	integer	no
user.stream_max	integer	no
user.tzname_max	integer	no

EXAMPLES

---

Example 1 Getting the Maximum Number of Processes




The following example gets the maximum number of processes allowed in the system:

sysctl kern.maxproc

---

---

Example 2 Setting the Maximum Number of Processes




The following example sets the maximum number of processes allowed in the system to 1000:

sysctl -w kern.maxproc=1000

---

---

Example 3 Getting System Clock Rate Information




The following example retrieves the system clock rate:

sysctl kern.clockrate

---

---

Example 4 Getting Load Average History




The following example retrieves the load average history for the system:

sysctl vm.loadavg

---

More variables than these are available, and the best and likely only place to find their deeper meanings is undoubtedly the source where they are defined.

FILES

For more information see the following files:

<netinet/icmp_var.h>

Definitions for fourth level ICMP identifiers

<netinet/in.h>

Definitions for third level Internet identifiers and fourth level IP identifiers

<netinet/udp_var.h>

Definitions for fourth level UDP identifiers

<sys/gmon.h>

Definitions for third level profiling identifiers

<sys/socket.h>

Definitions for second level network identifiers

<sys/sysctl.h>

Definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers

<vm/vm_param.h>

Definitions for second level virtual memory identifiers.

ATTRIBUTES

See attributes(5) for descriptions of the following attributes:

ATTRIBUTE TYPE	ATTRIBUTE VALUE
Interface Stability	Evolving

SEE ALSO

sysctl(3POSIX)

BUGS

sysctl presently exploits an undocumented interface to the kernel sysctl() facility to traverse the sysctl tree and to retrieve format and name information. The correct interface is being discussed.

ChorusOS 4.0  Last Revised December 1999

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXTENDED DESCRIPTION | EXAMPLES | FILES | ATTRIBUTES | SEE ALSO | BUGS