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