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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 1.3 2004/04/22 16:52:55 dillon 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
184 .Aq Pa sys/sysctl.h ,
186 The next and subsequent levels down are found in the include files
187 listed here, and described in separate sections below.
189 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
190 .It Sy "Name Next level names Description"
191 .It "CTL\_DEBUG sys/sysctl.h Debugging"
192 .It "CTL\_VFS sys/mount.h Filesystem"
193 .It "CTL\_HW sys/sysctl.h Generic CPU, I/O"
194 .It "CTL\_KERN sys/sysctl.h High kernel limits"
195 .It "CTL\_MACHDEP sys/sysctl.h Machine dependent"
196 .It "CTL\_NET sys/socket.h Networking"
197 .It "CTL\_USER sys/sysctl.h User-level"
198 .It "CTL\_VM vm/vm_param.h Virtual memory"
201 For example, the following retrieves the maximum number of processes allowed
204 .Bd -literal -offset indent -compact
209 mib[1] = KERN_MAXPROC;
210 len = sizeof(maxproc);
211 sysctl(mib, 2, &maxproc, &len, NULL, 0);
214 To retrieve the standard search path for the system utilities:
216 .Bd -literal -offset indent -compact
222 mib[1] = USER_CS_PATH;
223 sysctl(mib, 2, NULL, &len, NULL, 0);
225 sysctl(mib, 2, p, &len, NULL, 0);
228 The debugging variables vary from system to system.
229 A debugging variable may be added or deleted without need to recompile
234 gets the list of debugging variables from the kernel and
235 displays their current values.
236 The system defines twenty
237 .Ns ( Va struct ctldebug )
242 They are declared as separate variables so that they can be
243 individually initialized at the location of their associated variable.
244 The loader prevents multiple use of the same variable by issuing errors
245 if a variable is initialized in more than one place.
246 For example, to export the variable
248 as a debugging variable, the following declaration would be used:
249 .Bd -literal -offset indent -compact
250 int dospecialcheck = 1;
251 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
254 A distinguished second level name, VFS_GENERIC,
255 is used to get general information about all filesystems.
256 One of its third level identifiers is VFS_MAXTYPENUM
257 that gives the highest valid filesystem type number.
258 Its other third level identifier is VFS_CONF that
259 returns configuration information about the filesystem
260 type given as a fourth level identifier (see
262 as an example of its use).
263 The remaining second level identifiers are the
264 filesystem type number returned by a
266 call or from VFS_CONF.
267 The third level identifiers available for each filesystem
268 are given in the header file that defines the mount
269 argument structure for that filesystem.
271 The string and integer information available for the CTL_HW level
273 The changeable column shows whether a process with appropriate
274 privilege may change the value.
275 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
276 .It Sy "Second level name Type Changeable"
277 .It "HW\_MACHINE string no"
278 .It "HW\_MODEL string no"
279 .It "HW\_NCPU integer no"
280 .It "HW\_BYTEORDER integer no"
281 .It "HW\_PHYSMEM integer no"
282 .It "HW\_USERMEM integer no"
283 .It "HW\_PAGESIZE integer no"
284 .It "HW\_FLOATINGPOINT integer no"
285 .It "HW\_MACHINE\_ARCH string no"
286 .\".It "HW\_DISKNAMES integer no"
287 .\".It "HW\_DISKSTATS integer no"
298 The byteorder (4,321, or 1,234).
300 The bytes of physical memory.
302 The bytes of non-kernel memory.
304 The software page size.
305 .It Li HW_FLOATINGPOINT
306 Nonzero if the floating point support is in hardware.
307 .It Li HW_MACHINE_ARCH
308 The machine dependent architecture type.
309 .\".It Fa HW_DISKNAMES
310 .\".It Fa HW_DISKSTATS
313 The string and integer information available for the CTL_KERN level
315 The changeable column shows whether a process with appropriate
316 privilege may change the value.
317 The types of data currently available are process information,
318 system vnodes, the open file entries, routing table entries,
319 virtual memory statistics, load average history, and clock rate
321 .Bl -column "KERNXMAXPOSIXLOCKSPERUIDXXX" "struct clockrateXXX" -offset indent
322 .It Sy "Second level name Type Changeable"
323 .It "KERN\_ARGMAX integer no"
324 .It "KERN\_BOOTFILE string yes"
325 .It "KERN\_BOOTTIME struct timeval no"
326 .It "KERN\_CLOCKRATE struct clockinfo no"
327 .It "KERN\_FILE struct file no"
328 .It "KERN\_HOSTID integer yes"
329 .It "KERN\_HOSTNAME string yes"
330 .It "KERN\_JOB\_CONTROL integer no"
331 .It "KERN\_MAXFILES integer yes"
332 .It "KERN\_MAXFILESPERPROC integer yes"
333 .It "KERN\_MAXPOSIXLOCKSPERUID integer yes"
334 .It "KERN\_MAXPROC integer no"
335 .It "KERN\_MAXPROCPERUID integer yes"
336 .It "KERN\_MAXVNODES integer yes"
337 .It "KERN\_NGROUPS integer no"
338 .It "KERN\_NISDOMAINNAME string yes"
339 .It "KERN\_OSRELDATE integer no"
340 .It "KERN\_OSRELEASE string no"
341 .It "KERN\_OSREV integer no"
342 .It "KERN\_OSTYPE string no"
343 .It "KERN\_POSIX1 integer no"
344 .It "KERN\_PROC struct proc no"
345 .It "KERN\_PROF node not applicable"
346 .It "KERN\_QUANTUM integer yes"
347 .It "KERN\_SAVED\_IDS integer no"
348 .It "KERN\_SECURELVL integer raise only"
349 .It "KERN\_UPDATEINTERVAL integer no"
350 .It "KERN\_VERSION string no"
351 .It "KERN\_VNODE struct vnode no"
356 The maximum bytes of argument to
359 The full pathname of the file from which the kernel was loaded.
363 structure is returned.
364 This structure contains the time that the system was booted.
365 .It Li KERN_CLOCKRATE
368 structure is returned.
369 This structure contains the clock, statistics clock and profiling clock
370 frequencies, the number of micro-seconds per hz tick and the skew rate.
372 Return the entire file table.
373 The returned data consists of a single
375 followed by an array of
377 whose size depends on the current number of such objects in the system.
379 Get or set the host id.
381 Get or set the hostname.
382 .It Li KERN_JOB_CONTROL
383 Return 1 if job control is available on this system, otherwise 0.
385 The maximum number of files that may be open in the system.
386 .It Li KERN_MAXFILESPERPROC
387 The maximum number of files that may be open for a single process.
388 This limit only applies to processes with an effective uid of nonzero
389 at the time of the open request.
390 Files that have already been opened are not affected if the limit
391 or the effective uid is changed.
393 The maximum number of concurrent processes the system will allow.
394 .It Li KERN_MAXPROCPERUID
395 The maximum number of concurrent processes the system will allow
396 for a single effective uid.
397 This limit only applies to processes with an effective uid of nonzero
398 at the time of a fork request.
399 Processes that have already been started are not affected if the limit
401 .It Li KERN_MAXVNODES
402 The maximum number of vnodes available on the system.
404 The maximum number of supplemental groups.
405 .It Li KERN_NISDOMAINNAME
406 The name of the current YP/NIS domain.
407 .It Li KERN_OSRELDATE
408 The system release date in YYYYMM format
409 (January 1996 is encoded as 199601).
410 .It Li KERN_OSRELEASE
411 The system release string.
413 The system revision string.
415 The system type string.
419 with which the system
422 Return the entire process table, or a subset of it.
424 .Va struct kinfo_proc
425 structures is returned,
426 whose size depends on the current number of such objects in the system.
427 The third and fourth level names are as follows:
428 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
429 .It "Third level name Fourth level is:"
430 .It "KERN\_PROC\_ALL None"
431 .It "KERN\_PROC\_PID A process ID"
432 .It "KERN\_PROC\_PGRP A process group"
433 .It "KERN\_PROC\_TTY A tty device"
434 .It "KERN\_PROC\_UID A user ID"
435 .It "KERN\_PROC\_RUID A real user ID"
438 Return profiling information about the kernel.
439 If the kernel is not compiled for profiling,
440 attempts to retrieve any of the KERN_PROF values will
443 The third level names for the string and integer profiling information
445 The changeable column shows whether a process with appropriate
446 privilege may change the value.
447 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
448 .It Sy "Third level name Type Changeable"
449 .It "GPROF\_STATE integer yes"
450 .It "GPROF\_COUNT u_short[\|] yes"
451 .It "GPROF\_FROMS u_short[\|] yes"
452 .It "GPROF\_TOS struct tostruct yes"
453 .It "GPROF\_GMONPARAM struct gmonparam no"
456 The variables are as follows:
459 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
460 is running or stopped.
462 Array of statistical program counter counts.
464 Array indexed by program counter of call-from points.
468 describing destination of calls and their counts.
469 .It Li GPROF_GMONPARAM
470 Structure giving the sizes of the above arrays.
473 The maximum period of time, in microseconds, for which a process is allowed
474 to run without being preempted if other processes are in the run queue.
475 .It Li KERN_SAVED_IDS
476 Returns 1 if saved set-group and saved set-user ID is available.
477 .It Li KERN_SECURELVL
478 The system security level.
479 This level may be raised by processes with appropriate privilege.
480 It may not be lowered.
482 The system version string.
484 Return the entire vnode table.
485 Note, the vnode table is not necessarily a consistent snapshot of
487 The returned data consists of an array whose size depends on the
488 current number of such objects in the system.
489 Each element of the array contains the kernel address of a vnode
491 followed by the vnode itself
495 The set of variables defined is architecture dependent.
496 The following variables are defined for the i386 architecture.
497 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
498 .It Sy "Second level name Type Changeable"
499 .It Li "CPU_CONSDEV dev_t no"
500 .It Li "CPU_ADJKERNTZ int yes"
501 .It Li "CPU_DISRTCSET int yes"
502 .It Li "CPU_BOOTINFO struct bootinfo no"
503 .It Li "CPU_WALLCLOCK int yes"
506 The string and integer information available for the CTL_NET level
508 The changeable column shows whether a process with appropriate
509 privilege may change the value.
510 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
511 .It Sy "Second level name Type Changeable"
512 .It "PF\_ROUTE routing messages no"
513 .It "PF\_INET IPv4 values yes"
514 .It "PF\_INET6 IPv6 values yes"
519 Return the entire routing table or a subset of it.
520 The data is returned as a sequence of routing messages (see
522 for the header file, format and meaning).
523 The length of each message is contained in the message header.
525 The third level name is a protocol number, which is currently always 0.
526 The fourth level name is an address family, which may be set to 0 to
527 select all address families.
528 The fifth and sixth level names are as follows:
529 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
530 .It Sy "Fifth level name Sixth level is:"
531 .It "NET\_RT\_FLAGS rtflags"
532 .It "NET\_RT\_DUMP None"
533 .It "NET\_RT\_IFLIST None"
536 Get or set various global information about the IPv4
537 (Internet Protocol version 4).
538 The third level name is the protocol.
539 The fourth level name is the variable name.
540 The currently defined protocols and names are:
541 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
542 .It Sy "Protocol Variable Type Changeable"
543 .It "icmp bmcastecho integer yes"
544 .It "icmp maskrepl integer yes"
545 .It "ip forwarding integer yes"
546 .It "ip redirect integer yes"
547 .It "ip ttl integer yes"
548 .It "udp checksum integer yes"
551 The variables are as follows:
553 .It Li icmp.bmcastecho
554 Returns 1 if an ICMP echo request to a broadcast or multicast address is
557 Returns 1 if ICMP network mask requests are to be answered.
559 Returns 1 when IP forwarding is enabled for the host,
560 meaning that the host is acting as a router.
562 Returns 1 when ICMP redirects may be sent by the host.
563 This option is ignored unless the host is routing IP packets,
564 and should normally be enabled on all systems.
566 The maximum time-to-live (hop count) value for an IP packet sourced by
568 This value applies to normal transport protocols, not to ICMP.
570 Returns 1 when UDP checksums are being computed and checked.
571 Disabling UDP checksums is strongly discouraged.
573 For variables net.inet.*.ipsec, please refer to
577 Get or set various global information about the IPv6
578 (Internet Protocol version 6).
579 The third level name is the protocol.
580 The fourth level name is the variable name.
582 For variables net.inet6.* please refer to
584 For variables net.inet6.*.ipsec6, please refer to
588 The string and integer information available for the CTL_USER level
590 The changeable column shows whether a process with appropriate
591 privilege may change the value.
592 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
593 .It Sy "Second level name Type Changeable"
594 .It "USER\_BC\_BASE\_MAX integer no"
595 .It "USER\_BC\_DIM\_MAX integer no"
596 .It "USER\_BC\_SCALE\_MAX integer no"
597 .It "USER\_BC\_STRING\_MAX integer no"
598 .It "USER\_COLL\_WEIGHTS\_MAX integer no"
599 .It "USER\_CS\_PATH string no"
600 .It "USER\_EXPR\_NEST\_MAX integer no"
601 .It "USER\_LINE\_MAX integer no"
602 .It "USER\_POSIX2\_CHAR\_TERM integer no"
603 .It "USER\_POSIX2\_C\_BIND integer no"
604 .It "USER\_POSIX2\_C\_DEV integer no"
605 .It "USER\_POSIX2\_FORT\_DEV integer no"
606 .It "USER\_POSIX2\_FORT\_RUN integer no"
607 .It "USER\_POSIX2\_LOCALEDEF integer no"
608 .It "USER\_POSIX2\_SW\_DEV integer no"
609 .It "USER\_POSIX2\_UPE integer no"
610 .It "USER\_POSIX2\_VERSION integer no"
611 .It "USER\_RE\_DUP\_MAX integer no"
612 .It "USER\_STREAM\_MAX integer no"
613 .It "USER\_TZNAME\_MAX integer no"
617 .It Li USER_BC_BASE_MAX
618 The maximum ibase/obase values in the
621 .It Li USER_BC_DIM_MAX
622 The maximum array size in the
625 .It Li USER_BC_SCALE_MAX
626 The maximum scale value in the
629 .It Li USER_BC_STRING_MAX
630 The maximum string length in the
633 .It Li USER_COLL_WEIGHTS_MAX
634 The maximum number of weights that can be assigned to any entry of
635 the LC_COLLATE order keyword in the locale definition file.
637 Return a value for the
639 environment variable that finds all the standard utilities.
640 .It Li USER_EXPR_NEST_MAX
641 The maximum number of expressions that can be nested within
646 The maximum length in bytes of a text-processing utility's input
648 .It Li USER_POSIX2_CHAR_TERM
649 Return 1 if the system supports at least one terminal type capable of
650 all operations described in
653 .It Li USER_POSIX2_C_BIND
654 Return 1 if the system's C-language development facilities support the
655 C-Language Bindings Option, otherwise 0.
656 .It Li USER_POSIX2_C_DEV
657 Return 1 if the system supports the C-Language Development Utilities Option,
659 .It Li USER_POSIX2_FORT_DEV
660 Return 1 if the system supports the FORTRAN Development Utilities Option,
662 .It Li USER_POSIX2_FORT_RUN
663 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
665 .It Li USER_POSIX2_LOCALEDEF
666 Return 1 if the system supports the creation of locales, otherwise 0.
667 .It Li USER_POSIX2_SW_DEV
668 Return 1 if the system supports the Software Development Utilities Option,
670 .It Li USER_POSIX2_UPE
671 Return 1 if the system supports the User Portability Utilities Option,
673 .It Li USER_POSIX2_VERSION
676 with which the system attempts to comply.
677 .It Li USER_RE_DUP_MAX
678 The maximum number of repeated occurrences of a regular expression
679 permitted when using interval notation.
680 .It Li USER_STREAM_MAX
681 The minimum maximum number of streams that a process may have open
683 .It Li USER_TZNAME_MAX
684 The minimum maximum number of types supported for the name of a
688 The string and integer information available for the CTL_VM level
690 The changeable column shows whether a process with appropriate
691 privilege may change the value.
692 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
693 .It Sy "Second level name Type Changeable"
694 .It "VM\_LOADAVG struct loadavg no"
695 .It "VM\_METER struct vmtotal no"
696 .It "VM\_PAGEOUT\_ALGORITHM integer yes"
697 .It "VM\_SWAPPING\_ENABLED integer maybe"
698 .It "VM\_V\_CACHE\_MAX integer yes"
699 .It "VM\_V\_CACHE\_MIN integer yes"
700 .It "VM\_V\_FREE\_MIN integer yes"
701 .It "VM\_V\_FREE\_RESERVED integer yes"
702 .It "VM\_V\_FREE\_TARGET integer yes"
703 .It "VM\_V\_INACTIVE\_TARGET integer yes"
704 .It "VM\_V\_PAGEOUT\_FREE\_MIN integer yes"
709 Return the load average history.
710 The returned data consists of a
713 Return the system wide virtual memory statistics.
714 The returned data consists of a
716 .It Li VM_PAGEOUT_ALGORITHM
717 0 if the statistics-based page management algorithm is in use
718 or 1 if the near-LRU algorithm is in use.
719 .It Li VM_SWAPPING_ENABLED
720 1 if process swapping is enabled or 0 if disabled. This variable is
721 permanently set to 0 if the kernel was built with swapping disabled.
722 .It Li VM_V_CACHE_MAX
723 Maximum desired size of the cache queue.
724 .It Li VM_V_CACHE_MIN
725 Minimum desired size of the cache queue. If the cache queue size
726 falls very far below this value, the pageout daemon is awakened.
728 Minimum amount of memory (cache memory plus free memory)
729 required to be available before a process waiting on memory will be
731 .It Li VM_V_FREE_RESERVED
732 Processes will awaken the pageout daemon and wait for memory if the
733 number of free and cached pages drops below this value.
734 .It Li VM_V_FREE_TARGET
735 The total amount of free memory (including cache memory) that the
736 pageout daemon tries to maintain.
737 .It Li VM_V_INACTIVE_TARGET
738 The desired number of inactive pages that the pageout daemon should
739 achieve when it runs. Inactive pages can be quickly inserted into
740 process address space when needed.
741 .It Li VM_V_PAGEOUT_FREE_MIN
742 If the amount of free and cache memory falls below this value, the
743 pageout daemon will enter "memory conserving mode" to avoid deadlock.
748 The following errors may be reported:
757 contains an invalid address.
761 array is less than two or greater than CTL_MAXNAME.
765 is given and its specified length in
767 is too large or too small.
769 The length pointed to by
771 is too short to hold the requested value.
775 array specifies an intermediate rather than terminal name.
779 array specifies a terminal name, but the actual name is not terminal.
783 array specifies a value that is unknown.
785 An attempt is made to set a read-only value.
787 A process without appropriate privilege attempts to set a value.
790 .Bl -tag -width <netinet/icmpXvar.h> -compact
791 .It Aq Pa sys/sysctl.h
792 definitions for top level identifiers, second level kernel and hardware
793 identifiers, and user level identifiers
794 .It Aq Pa sys/socket.h
795 definitions for second level network identifiers
797 definitions for third level profiling identifiers
798 .It Aq Pa vm/vm_param.h
799 definitions for second level virtual memory identifiers
800 .It Aq Pa netinet/in.h
801 definitions for third level IPv4/IPv6 identifiers and
802 fourth level IPv4/v6 identifiers
803 .It Aq Pa netinet/icmp_var.h
804 definitions for fourth level ICMP identifiers
805 .It Aq Pa netinet/icmp6.h
806 definitions for fourth level ICMPv6 identifiers
807 .It Aq Pa netinet/udp_var.h
808 definitions for fourth level UDP identifiers
816 function first appeared in