sysctl(8) manual page

The 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 following options are available:

-A Equivalent to -o -a (for compatibility).

-a List all the currently available values except for those which are opaque or excluded from listing via the CTLFLAG_SKIP flag. This option is ignored if one or more variable names are specified on the command line.

-B bufsize

Set the buffer size to read from the sysctl to bufsize. This is necessary for a sysctl that has variable length, and the probe value of 0 is a valid length, such as kern.arandom.

-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 sysctl utility. This option is ignored if either -N or -n is specified, or a variable is being set.

-F Print the format of the variable. This is additional information to describe the type of the variable and most useful with struct types such as clockinfo, timeval, and loadavg.

-f filename

Specify a file which contains a pair of name and value in each line. sysctl reads and processes the specified file first and then processes the name and value pairs in the command line argument. Note that when the -j jail option is specified, the file will be opened before attaching to the jail and then be processed inside the jail.

-h Format output for human, rather than machine, readability.

-i Ignore unknown OIDs. The purpose is to make use of sysctl for collecting data from a variety of machines (not all of which are necessarily running exactly the same software) easier.

-J Display only jail prision sysctl variables (CTLFLAG_PRISON).

-j jail

Perform the actions inside the jail (by jail id or jail name).

-l Show the length of variables along with their values. This option cannot be combined with the -N option.

-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) ( ports/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 Do not show variable 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 sysctl to standard error.

-T Display only variables that are settable via loader (CTLFLAG_TUN).

-t Print the type of the variable.

-V Display only VNET sysctl variables (CTLFLAG_VNET).

-W Display only writable variables that are not statistical. Useful for determining the set of runtime tunable sysctls.

-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 sysctl consists of integers, strings, and opaque types. The sysctl 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.conf(5). Please refer to loader.conf(5) 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 variables see sysctl(3) and security(7).

The changeable column indicates whether a process with appropriate privilege can change the value. String and integer values can be set using sysctl.

Name Ta Type Changeable
kern.ostype Ta string no
kern.osrelease Ta string no
kern.osrevision Ta integer no
kern.version Ta string no
kern.maxvnodes Ta integer yes
kern.maxproc Ta integer no
kern.maxprocperuid Ta integer yes
kern.maxfiles Ta integer yes
kern.maxfilesperproc Ta integer yes
kern.argmax Ta integer no
kern.securelevel Ta integer raise only
kern.hostname Ta string yes
kern.hostid Ta integer yes
kern.clockrate Ta struct no
kern.posix1version Ta integer no
kern.ngroups Ta integer no
kern.job_control Ta integer no
kern.saved_ids Ta integer no
kern.boottime Ta struct no
kern.domainname Ta string yes
kern.filedelay Ta integer yes
kern.dirdelay Ta integer yes
kern.metadelay Ta integer yes
kern.osreldate Ta integer no
kern.bootfile Ta string yes
kern.corefile Ta string yes
kern.logsigexit Ta integer yes
security.bsd.suser_enabled Ta integer yes
security.bsd.see_other_uids Ta integer yes
security.bsd.see_other_gids Ta integer yes
security.bsd.see_jail_proc Ta integer yes
security.bsd.unprivileged_proc_debug Ta integer yes
security.bsd.unprivileged_read_msgbuf Ta integer yes
vm.loadavg Ta struct no
hw.machine Ta string no
hw.model Ta string no
hw.ncpu Ta integer no
hw.byteorder Ta integer no
hw.physmem Ta integer no
hw.usermem Ta integer no
hw.pagesize Ta integer no
hw.floatingpoint Ta integer no
hw.machine_arch Ta string no
hw.realmem Ta integer no
machdep.adjkerntz Ta integer yes
machdep.disable_rtc_set Ta integer yes
machdep.guessed_bootdev Ta string no
user.cs_path Ta string no
user.bc_base_max Ta integer no
user.bc_dim_max Ta integer no
user.bc_scale_max Ta integer no
user.bc_string_max Ta integer no
user.coll_weights_max Ta integer no
user.expr_nest_max Ta integer no
user.line_max Ta integer no
user.re_dup_max Ta integer no
user.posix2_version Ta integer no
user.posix2_c_bind Ta integer no
user.posix2_c_dev Ta integer no
user.posix2_char_term Ta integer no
user.posix2_fort_dev Ta integer no
user.posix2_fort_run Ta integer no
user.posix2_localedef Ta integer no
user.posix2_sw_dev Ta integer no
user.posix2_upe Ta integer no
user.stream_max Ta integer no
user.tzname_max Ta integer no
user.localbase Ta string no

`<sys/sysctl.h>`	definitions for top level identifiers, second level kernel and hardware identifiers, and user level identifiers
`<sys/socket.h>`	definitions for second level network identifiers
`<sys/gmon.h>`	definitions for third level profiling identifiers
`<vm/vm_param.h>`	definitions for second level virtual memory identifiers
`<netinet/in.h>`	definitions for third level Internet identifiers and fourth level IP identifiers
`<netinet/icmp_var.h>`
	definitions for fourth level ICMP identifiers
`<netinet/udp_var.h>`
	definitions for fourth level UDP identifiers

Manual Pages — SYSCTL

NAME

CONTENTS

SYNOPSIS

DESCRIPTION

FILES

EXIT STATUS

EXAMPLES

COMPATIBILITY

SEE ALSO

HISTORY

BUGS

-A	Equivalent to -o -a (for compatibility).
-a	List all the currently available values except for those which are opaque or excluded from listing via the `CTLFLAG_SKIP` flag. This option is ignored if one or more variable names are specified on the command line.
-B bufsize
	Set the buffer size to read from the sysctl to bufsize. This is necessary for a sysctl that has variable length, and the probe value of 0 is a valid length, such as kern.arandom.
-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 sysctl utility. This option is ignored if either -N or -n is specified, or a variable is being set.
-F	Print the format of the variable. This is additional information to describe the type of the variable and most useful with struct types such as clockinfo, timeval, and loadavg.
-f filename
	Specify a file which contains a pair of name and value in each line. sysctl reads and processes the specified file first and then processes the name and value pairs in the command line argument. Note that when the -j jail option is specified, the file will be opened before attaching to the jail and then be processed inside the jail.
-h	Format output for human, rather than machine, readability.
-i	Ignore unknown OIDs. The purpose is to make use of sysctl for collecting data from a variety of machines (not all of which are necessarily running exactly the same software) easier.
-J	Display only jail prision sysctl variables (CTLFLAG_PRISON).
-j jail
	Perform the actions inside the jail (by jail id or jail name).
-l	Show the length of variables along with their values. This option cannot be combined with the -N option.
-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) ( `ports/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	Do not show variable 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 sysctl to standard error.
-T	Display only variables that are settable via loader (CTLFLAG_TUN).
-t	Print the type of the variable.
-V	Display only VNET sysctl variables (CTLFLAG_VNET).
-W	Display only writable variables that are not statistical. Useful for determining the set of runtime tunable sysctls.
-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.

Name Ta Type	Changeable
kern.ostype Ta string	no
kern.osrelease Ta string	no
kern.osrevision Ta integer	no
kern.version Ta string	no
kern.maxvnodes Ta integer	yes
kern.maxproc Ta integer	no
kern.maxprocperuid Ta integer	yes
kern.maxfiles Ta integer	yes
kern.maxfilesperproc Ta integer	yes
kern.argmax Ta integer	no
kern.securelevel Ta integer	raise only
kern.hostname Ta string	yes
kern.hostid Ta integer	yes
kern.clockrate Ta struct	no
kern.posix1version Ta integer	no
kern.ngroups Ta integer	no
kern.job_control Ta integer	no
kern.saved_ids Ta integer	no
kern.boottime Ta struct	no
kern.domainname Ta string	yes
kern.filedelay Ta integer	yes
kern.dirdelay Ta integer	yes
kern.metadelay Ta integer	yes
kern.osreldate Ta integer	no
kern.bootfile Ta string	yes
kern.corefile Ta string	yes
kern.logsigexit Ta integer	yes
security.bsd.suser_enabled Ta integer	yes
security.bsd.see_other_uids Ta integer	yes
security.bsd.see_other_gids Ta integer	yes
security.bsd.see_jail_proc Ta integer	yes
security.bsd.unprivileged_proc_debug Ta integer	yes
security.bsd.unprivileged_read_msgbuf Ta integer	yes
vm.loadavg Ta struct	no
hw.machine Ta string	no
hw.model Ta string	no
hw.ncpu Ta integer	no
hw.byteorder Ta integer	no
hw.physmem Ta integer	no
hw.usermem Ta integer	no
hw.pagesize Ta integer	no
hw.floatingpoint Ta integer	no
hw.machine_arch Ta string	no
hw.realmem Ta integer	no
machdep.adjkerntz Ta integer	yes
machdep.disable_rtc_set Ta integer	yes
machdep.guessed_bootdev Ta string	no
user.cs_path Ta string	no
user.bc_base_max Ta integer	no
user.bc_dim_max Ta integer	no
user.bc_scale_max Ta integer	no
user.bc_string_max Ta integer	no
user.coll_weights_max Ta integer	no
user.expr_nest_max Ta integer	no
user.line_max Ta integer	no
user.re_dup_max Ta integer	no
user.posix2_version Ta integer	no
user.posix2_c_bind Ta integer	no
user.posix2_c_dev Ta integer	no
user.posix2_char_term Ta integer	no
user.posix2_fort_dev Ta integer	no
user.posix2_fort_run Ta integer	no
user.posix2_localedef Ta integer	no
user.posix2_sw_dev Ta integer	no
user.posix2_upe Ta integer	no
user.stream_max Ta integer	no
user.tzname_max Ta integer	no
user.localbase Ta string	no