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28 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
29 .\" $FreeBSD: src/lib/libc/gen/sysctl.3,v 1.33.2.13 2002/04/07 04:57:14 dd Exp $
30 .\" $DragonFly: src/lib/libc/gen/sysctl.3,v 1.10 2008/05/02 02:05:03 swildner Exp $
39 .Nd get or set system information
46 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
48 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
50 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
54 function retrieves system information and allows processes with
55 appropriate privileges to set system information.
56 The information available from
58 consists of integers, strings, and tables.
59 Information may be retrieved and set from the command interface
64 Unless explicitly noted below,
66 returns a consistent snapshot of the data requested.
67 Consistency is obtained by locking the destination
68 buffer into memory so that the data may be copied out without blocking.
71 are serialized to avoid deadlock.
73 The state is described using a ``Management Information Base'' (MIB)
78 length array of integers.
82 function accepts an ASCII representation of the name and internally
83 looks up the integer name vector. Apart from that, it behaves the same
88 The information is copied into the buffer specified by
90 The size of the buffer is given by the location specified by
93 and that location gives the amount of data copied after a successful call
94 and after a call that returns with the error code
96 If the amount of data available is greater
97 than the size of the buffer supplied,
98 the call supplies as much data as fits in the buffer provided
99 and returns with the error code
101 If the old value is not desired,
105 should be set to NULL.
107 The size of the available data can be determined by calling
109 with a NULL parameter for
111 The size of the available data will be returned in the location pointed to by
113 For some operations, the amount of space may change often.
114 For these operations,
115 the system attempts to round up so that the returned size is
116 large enough for a call to return the data shortly thereafter.
120 is set to point to a buffer of length
122 from which the requested value is to be taken.
123 If a new value is not to be set,
125 should be set to NULL and
131 function accepts an ASCII representation of the name,
132 looks up the integer name vector,
133 and returns the numeric representation in the mib array pointed to by
135 The number of elements in the mib array is given by the location specified by
138 and that location gives the number of entries copied after a successful call.
143 may be used in subsequent
145 calls to get the data associated with the requested ASCII name.
146 This interface is intended for use by applications that want to
147 repeatedly request the same variable (the
149 function runs in about a third the time as the same request made via the
154 function is also useful for fetching mib prefixes and then adding
156 For example, to fetch process information
157 for processes with pid's less than 100:
159 .Bd -literal -offset indent -compact
162 struct kinfo_proc kp;
164 /* Fill out the first three components of the mib */
166 sysctlnametomib("kern.proc.pid", mib, &len);
168 /* Fetch and print entries for pid's < 100 */
169 for (i = 0; i < 100; i++) {
172 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
179 The top level names are defined with a CTL_ prefix in
182 The next and subsequent levels down are found in the include files
183 listed here, and described in separate sections below.
184 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
185 .It Sy "Name Next level names Description"
186 .It "CTL\_DEBUG sys/sysctl.h Debugging"
187 .It "CTL\_VFS sys/mount.h Filesystem"
188 .It "CTL\_HW sys/sysctl.h Generic CPU, I/O"
189 .It "CTL\_KERN sys/sysctl.h High kernel limits"
190 .It "CTL\_MACHDEP sys/sysctl.h Machine dependent"
191 .It "CTL\_NET sys/socket.h Networking"
192 .It "CTL\_USER sys/sysctl.h User-level"
193 .It "CTL\_VM vm/vm_param.h Virtual memory"
196 For example, the following retrieves the maximum number of processes allowed
199 .Bd -literal -offset indent -compact
204 mib[1] = KERN_MAXPROC;
205 len = sizeof(maxproc);
206 sysctl(mib, 2, &maxproc, &len, NULL, 0);
209 To retrieve the standard search path for the system utilities:
211 .Bd -literal -offset indent -compact
217 mib[1] = USER_CS_PATH;
218 sysctl(mib, 2, NULL, &len, NULL, 0);
220 sysctl(mib, 2, p, &len, NULL, 0);
223 The debugging variables vary from system to system.
224 A debugging variable may be added or deleted without need to recompile
229 gets the list of debugging variables from the kernel and
230 displays their current values.
231 The system defines twenty
232 .Ns ( Va struct ctldebug )
237 They are declared as separate variables so that they can be
238 individually initialized at the location of their associated variable.
239 The loader prevents multiple use of the same variable by issuing errors
240 if a variable is initialized in more than one place.
241 For example, to export the variable
243 as a debugging variable, the following declaration would be used:
244 .Bd -literal -offset indent -compact
245 int dospecialcheck = 1;
246 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
249 A distinguished second level name, VFS_GENERIC,
250 is used to get general information about all filesystems.
251 One of its third level identifiers is VFS_MAXTYPENUM
252 that gives the highest valid filesystem type number.
253 Its other third level identifier is VFS_CONF that
254 returns configuration information about the filesystem
255 type given as a fourth level identifier (see
257 as an example of its use).
258 The remaining second level identifiers are the
259 filesystem type number returned by a
261 call or from VFS_CONF.
262 The third level identifiers available for each filesystem
263 are given in the header file that defines the mount
264 argument structure for that filesystem.
266 The string and integer information available for the CTL_HW level
268 The changeable column shows whether a process with appropriate
269 privilege may change the value.
270 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
271 .It Sy "Second level name Type Changeable"
272 .It "HW\_MACHINE string no"
273 .It "HW\_MODEL string no"
274 .It "HW\_NCPU integer no"
275 .It "HW\_BYTEORDER integer no"
276 .It "HW\_PHYSMEM integer no"
277 .It "HW\_USERMEM integer no"
278 .It "HW\_PAGESIZE integer no"
279 .It "HW\_FLOATINGPOINT integer no"
280 .It "HW\_MACHINE\_ARCH string no"
281 .\".It "HW\_DISKNAMES integer no"
282 .\".It "HW\_DISKSTATS integer no"
283 .It "HW_SENSORS node not applicable"
293 The byteorder (4,321, or 1,234).
295 The bytes of physical memory.
297 The bytes of non-kernel memory.
299 The software page size.
300 .It Li HW_FLOATINGPOINT
301 Nonzero if the floating point support is in hardware.
302 .It Li HW_MACHINE_ARCH
303 The machine dependent architecture type.
304 .\".It Fa HW_DISKNAMES
305 .\".It Fa HW_DISKSTATS
307 Third level comprises an array of
308 .Vt "struct sensordev"
309 structures containing information about devices
310 that may attach hardware monitoring sensors.
312 Third, fourth and fifth levels together comprise an array of
314 structures containing snapshot readings of hardware monitoring sensors.
315 In such usage, third level indicates the numerical representation
316 of the sensor device name to which the sensor is attached
319 and number shall be matched with the help of
320 .Vt "struct sensordev"
322 fourth level indicates sensor type and
323 fifth level is an ordinal sensor number (unique to
324 the specified sensor type on the specified sensor device).
338 The string and integer information available for the CTL_KERN level
340 The changeable column shows whether a process with appropriate
341 privilege may change the value.
342 The types of data currently available are process information,
343 system vnodes, the open file entries, routing table entries,
344 virtual memory statistics, load average history, and clock rate
346 .Bl -column "KERNXMAXPOSIXLOCKSPERUIDXXX" "struct clockrateXXX" -offset indent
347 .It Sy "Second level name Type Changeable"
348 .It "KERN\_ARGMAX integer no"
349 .It "KERN\_BOOTFILE string yes"
350 .It "KERN\_BOOTTIME struct timeval no"
351 .It "KERN\_CLOCKRATE struct clockinfo no"
352 .It "KERN\_FILE struct file no"
353 .It "KERN\_HOSTID integer yes"
354 .It "KERN\_HOSTNAME string yes"
355 .It "KERN\_JOB\_CONTROL integer no"
356 .It "KERN\_MAXFILES integer yes"
357 .It "KERN\_MAXFILESPERPROC integer yes"
358 .It "KERN\_MAXPOSIXLOCKSPERUID integer yes"
359 .It "KERN\_MAXPROC integer no"
360 .It "KERN\_MAXPROCPERUID integer yes"
361 .It "KERN\_MAXVNODES integer yes"
362 .It "KERN\_NGROUPS integer no"
363 .It "KERN\_NISDOMAINNAME string yes"
364 .It "KERN\_OSRELDATE integer no"
365 .It "KERN\_OSRELEASE string no"
366 .It "KERN\_OSREV integer no"
367 .It "KERN\_OSTYPE string no"
368 .It "KERN\_POSIX1 integer no"
369 .It "KERN\_PROC struct proc no"
370 .It "KERN\_PROF node not applicable"
371 .It "KERN\_QUANTUM integer yes"
372 .It "KERN\_SAVED\_IDS integer no"
373 .It "KERN\_SECURELVL integer raise only"
374 .It "KERN\_UPDATEINTERVAL integer no"
375 .It "KERN\_VERSION string no"
376 .It "KERN\_VNODE struct vnode no"
380 The maximum bytes of argument to
383 The full pathname of the file from which the kernel was loaded.
387 structure is returned.
388 This structure contains the time that the system was booted.
389 .It Li KERN_CLOCKRATE
392 structure is returned.
393 This structure contains the clock, statistics clock and profiling clock
394 frequencies, the number of micro-seconds per hz tick and the skew rate.
396 Return the entire file table.
397 The returned data consists of a single
399 followed by an array of
401 whose size depends on the current number of such objects in the system.
403 Get or set the host id.
405 Get or set the hostname.
406 .It Li KERN_JOB_CONTROL
407 Return 1 if job control is available on this system, otherwise 0.
409 The maximum number of files that may be open in the system.
410 .It Li KERN_MAXFILESPERPROC
411 The maximum number of files that may be open for a single process.
412 This limit only applies to processes with an effective uid of nonzero
413 at the time of the open request.
414 Files that have already been opened are not affected if the limit
415 or the effective uid is changed.
417 The maximum number of concurrent processes the system will allow.
418 .It Li KERN_MAXPROCPERUID
419 The maximum number of concurrent processes the system will allow
420 for a single effective uid.
421 This limit only applies to processes with an effective uid of nonzero
422 at the time of a fork request.
423 Processes that have already been started are not affected if the limit
425 .It Li KERN_MAXVNODES
426 The maximum number of vnodes available on the system.
428 The maximum number of supplemental groups.
429 .It Li KERN_NISDOMAINNAME
430 The name of the current YP/NIS domain.
431 .It Li KERN_OSRELDATE
432 The system release date in YYYYMM format
433 (January 1996 is encoded as 199601).
434 .It Li KERN_OSRELEASE
435 The system release string.
437 The system revision string.
439 The system type string.
443 with which the system
446 Return the entire process table, or a subset of it.
448 .Va struct kinfo_proc
449 structures is returned,
450 whose size depends on the current number of such objects in the system.
451 The third and fourth level names are as follows:
452 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
453 .It "Third level name Fourth level is:"
454 .It "KERN\_PROC\_ALL None"
455 .It "KERN\_PROC\_PID A process ID"
456 .It "KERN\_PROC\_PGRP A process group"
457 .It "KERN\_PROC\_TTY A tty device"
458 .It "KERN\_PROC\_UID A user ID"
459 .It "KERN\_PROC\_RUID A real user ID"
463 .Li KERN_PROC_FLAG_LWP
464 to the third level name signals that information about all
465 light weight processes of the selected processes should be returned.
467 Return profiling information about the kernel.
468 If the kernel is not compiled for profiling,
469 attempts to retrieve any of the KERN_PROF values will
472 The third level names for the string and integer profiling information
474 The changeable column shows whether a process with appropriate
475 privilege may change the value.
476 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
477 .It Sy "Third level name Type Changeable"
478 .It "GPROF\_STATE integer yes"
479 .It "GPROF\_COUNT u_short[\|] yes"
480 .It "GPROF\_FROMS u_short[\|] yes"
481 .It "GPROF\_TOS struct tostruct yes"
482 .It "GPROF\_GMONPARAM struct gmonparam no"
485 The variables are as follows:
488 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
489 is running or stopped.
491 Array of statistical program counter counts.
493 Array indexed by program counter of call-from points.
497 describing destination of calls and their counts.
498 .It Li GPROF_GMONPARAM
499 Structure giving the sizes of the above arrays.
502 The maximum period of time, in microseconds, for which a process is allowed
503 to run without being preempted if other processes are in the run queue.
504 .It Li KERN_SAVED_IDS
505 Returns 1 if saved set-group and saved set-user ID is available.
506 .It Li KERN_SECURELVL
507 The system security level.
508 This level may be raised by processes with appropriate privilege.
509 It may not be lowered.
511 The system version string.
513 Return the entire vnode table.
514 Note, the vnode table is not necessarily a consistent snapshot of
516 The returned data consists of an array whose size depends on the
517 current number of such objects in the system.
518 Each element of the array contains the kernel address of a vnode
520 followed by the vnode itself
524 The set of variables defined is architecture dependent.
525 The following variables are defined for the i386 architecture.
526 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
527 .It Sy "Second level name Type Changeable"
528 .It Li "CPU_CONSDEV dev_t no"
529 .It Li "CPU_ADJKERNTZ int yes"
530 .It Li "CPU_DISRTCSET int yes"
531 .It Li "CPU_BOOTINFO struct bootinfo no"
532 .It Li "CPU_WALLCLOCK int yes"
535 The string and integer information available for the CTL_NET level
537 The changeable column shows whether a process with appropriate
538 privilege may change the value.
539 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
540 .It Sy "Second level name Type Changeable"
541 .It "PF\_ROUTE routing messages no"
542 .It "PF\_INET IPv4 values yes"
543 .It "PF\_INET6 IPv6 values yes"
547 Return the entire routing table or a subset of it.
548 The data is returned as a sequence of routing messages (see
550 for the header file, format and meaning).
551 The length of each message is contained in the message header.
553 The third level name is a protocol number, which is currently always 0.
554 The fourth level name is an address family, which may be set to 0 to
555 select all address families.
556 The fifth and sixth level names are as follows:
557 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
558 .It Sy "Fifth level name Sixth level is:"
559 .It "NET\_RT\_FLAGS rtflags"
560 .It "NET\_RT\_DUMP None"
561 .It "NET\_RT\_IFLIST None"
564 Get or set various global information about the IPv4
565 (Internet Protocol version 4).
566 The third level name is the protocol.
567 The fourth level name is the variable name.
568 The currently defined protocols and names are:
569 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
570 .It Sy "Protocol Variable Type Changeable"
571 .It "icmp bmcastecho integer yes"
572 .It "icmp maskrepl integer yes"
573 .It "ip forwarding integer yes"
574 .It "ip redirect integer yes"
575 .It "ip ttl integer yes"
576 .It "udp checksum integer yes"
579 The variables are as follows:
581 .It Li icmp.bmcastecho
582 Returns 1 if an ICMP echo request to a broadcast or multicast address is
585 Returns 1 if ICMP network mask requests are to be answered.
587 Returns 1 when IP forwarding is enabled for the host,
588 meaning that the host is acting as a router.
590 Returns 1 when ICMP redirects may be sent by the host.
591 This option is ignored unless the host is routing IP packets,
592 and should normally be enabled on all systems.
594 The maximum time-to-live (hop count) value for an IP packet sourced by
596 This value applies to normal transport protocols, not to ICMP.
598 Returns 1 when UDP checksums are being computed and checked.
599 Disabling UDP checksums is strongly discouraged.
601 For variables net.inet.*.ipsec, please refer to
605 Get or set various global information about the IPv6
606 (Internet Protocol version 6).
607 The third level name is the protocol.
608 The fourth level name is the variable name.
610 For variables net.inet6.* please refer to
612 For variables net.inet6.*.ipsec6, please refer to
616 The string and integer information available for the CTL_USER level
618 The changeable column shows whether a process with appropriate
619 privilege may change the value.
620 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
621 .It Sy "Second level name Type Changeable"
622 .It "USER\_BC\_BASE\_MAX integer no"
623 .It "USER\_BC\_DIM\_MAX integer no"
624 .It "USER\_BC\_SCALE\_MAX integer no"
625 .It "USER\_BC\_STRING\_MAX integer no"
626 .It "USER\_COLL\_WEIGHTS\_MAX integer no"
627 .It "USER\_CS\_PATH string no"
628 .It "USER\_EXPR\_NEST\_MAX integer no"
629 .It "USER\_LINE\_MAX integer no"
630 .It "USER\_POSIX2\_CHAR\_TERM integer no"
631 .It "USER\_POSIX2\_C\_BIND integer no"
632 .It "USER\_POSIX2\_C\_DEV integer no"
633 .It "USER\_POSIX2\_FORT\_DEV integer no"
634 .It "USER\_POSIX2\_FORT\_RUN integer no"
635 .It "USER\_POSIX2\_LOCALEDEF integer no"
636 .It "USER\_POSIX2\_SW\_DEV integer no"
637 .It "USER\_POSIX2\_UPE integer no"
638 .It "USER\_POSIX2\_VERSION integer no"
639 .It "USER\_RE\_DUP\_MAX integer no"
640 .It "USER\_STREAM\_MAX integer no"
641 .It "USER\_TZNAME\_MAX integer no"
644 .It Li USER_BC_BASE_MAX
645 The maximum ibase/obase values in the
648 .It Li USER_BC_DIM_MAX
649 The maximum array size in the
652 .It Li USER_BC_SCALE_MAX
653 The maximum scale value in the
656 .It Li USER_BC_STRING_MAX
657 The maximum string length in the
660 .It Li USER_COLL_WEIGHTS_MAX
661 The maximum number of weights that can be assigned to any entry of
662 the LC_COLLATE order keyword in the locale definition file.
664 Return a value for the
666 environment variable that finds all the standard utilities.
667 .It Li USER_EXPR_NEST_MAX
668 The maximum number of expressions that can be nested within
673 The maximum length in bytes of a text-processing utility's input
675 .It Li USER_POSIX2_CHAR_TERM
676 Return 1 if the system supports at least one terminal type capable of
677 all operations described in
680 .It Li USER_POSIX2_C_BIND
681 Return 1 if the system's C-language development facilities support the
682 C-Language Bindings Option, otherwise 0.
683 .It Li USER_POSIX2_C_DEV
684 Return 1 if the system supports the C-Language Development Utilities Option,
686 .It Li USER_POSIX2_FORT_DEV
687 Return 1 if the system supports the FORTRAN Development Utilities Option,
689 .It Li USER_POSIX2_FORT_RUN
690 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
692 .It Li USER_POSIX2_LOCALEDEF
693 Return 1 if the system supports the creation of locales, otherwise 0.
694 .It Li USER_POSIX2_SW_DEV
695 Return 1 if the system supports the Software Development Utilities Option,
697 .It Li USER_POSIX2_UPE
698 Return 1 if the system supports the User Portability Utilities Option,
700 .It Li USER_POSIX2_VERSION
703 with which the system attempts to comply.
704 .It Li USER_RE_DUP_MAX
705 The maximum number of repeated occurrences of a regular expression
706 permitted when using interval notation.
707 .It Li USER_STREAM_MAX
708 The minimum maximum number of streams that a process may have open
710 .It Li USER_TZNAME_MAX
711 The minimum maximum number of types supported for the name of a
715 The string and integer information available for the CTL_VM level
717 The changeable column shows whether a process with appropriate
718 privilege may change the value.
719 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
720 .It Sy "Second level name Type Changeable"
721 .It "VM\_LOADAVG struct loadavg no"
722 .It "VM\_METER struct vmtotal no"
723 .It "VM\_PAGEOUT\_ALGORITHM integer yes"
724 .It "VM\_SWAPPING\_ENABLED integer maybe"
725 .It "VM\_V\_CACHE\_MAX integer yes"
726 .It "VM\_V\_CACHE\_MIN integer yes"
727 .It "VM\_V\_FREE\_MIN integer yes"
728 .It "VM\_V\_FREE\_RESERVED integer yes"
729 .It "VM\_V\_FREE\_TARGET integer yes"
730 .It "VM\_V\_INACTIVE\_TARGET integer yes"
731 .It "VM\_V\_PAGEOUT\_FREE\_MIN integer yes"
735 Return the load average history.
736 The returned data consists of a
739 Return the system wide virtual memory statistics.
740 The returned data consists of a
742 .It Li VM_PAGEOUT_ALGORITHM
743 0 if the statistics-based page management algorithm is in use
744 or 1 if the near-LRU algorithm is in use.
745 .It Li VM_SWAPPING_ENABLED
746 1 if process swapping is enabled or 0 if disabled. This variable is
747 permanently set to 0 if the kernel was built with swapping disabled.
748 .It Li VM_V_CACHE_MAX
749 Maximum desired size of the cache queue.
750 .It Li VM_V_CACHE_MIN
751 Minimum desired size of the cache queue. If the cache queue size
752 falls very far below this value, the pageout daemon is awakened.
754 Minimum amount of memory (cache memory plus free memory)
755 required to be available before a process waiting on memory will be
757 .It Li VM_V_FREE_RESERVED
758 Processes will awaken the pageout daemon and wait for memory if the
759 number of free and cached pages drops below this value.
760 .It Li VM_V_FREE_TARGET
761 The total amount of free memory (including cache memory) that the
762 pageout daemon tries to maintain.
763 .It Li VM_V_INACTIVE_TARGET
764 The desired number of inactive pages that the pageout daemon should
765 achieve when it runs. Inactive pages can be quickly inserted into
766 process address space when needed.
767 .It Li VM_V_PAGEOUT_FREE_MIN
768 If the amount of free and cache memory falls below this value, the
769 pageout daemon will enter "memory conserving mode" to avoid deadlock.
774 .Bl -tag -width ".In netinet/icmp_var.h" -compact
776 definitions for top level identifiers, second level kernel and hardware
777 identifiers, and user level identifiers
779 definitions for second level network identifiers
781 definitions for third level profiling identifiers
783 definitions for second level virtual memory identifiers
785 definitions for third level IPv4/IPv6 identifiers and
786 fourth level IPv4/v6 identifiers
787 .It In netinet/icmp_var.h
788 definitions for fourth level ICMP identifiers
789 .It In netinet/icmp6.h
790 definitions for fourth level ICMPv6 identifiers
791 .It In netinet/udp_var.h
792 definitions for fourth level UDP identifiers
795 The following errors may be reported:
804 contains an invalid address.
808 array is less than two or greater than CTL_MAXNAME.
812 is given and its specified length in
814 is too large or too small.
816 The length pointed to by
818 is too short to hold the requested value.
822 array specifies an intermediate rather than terminal name.
826 array specifies a terminal name, but the actual name is not terminal.
830 array specifies a value that is unknown.
832 An attempt is made to set a read-only value.
834 A process without appropriate privilege attempts to set a value.
842 function first appeared in