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14 .\" This product includes software developed by the University of
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20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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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 $
42 .Nd get or set system information
49 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
51 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
53 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
57 function retrieves system information and allows processes with
58 appropriate privileges to set system information.
59 The information available from
61 consists of integers, strings, and tables.
62 Information may be retrieved and set from the command interface
67 Unless explicitly noted below,
69 returns a consistent snapshot of the data requested.
70 Consistency is obtained by locking the destination
71 buffer into memory so that the data may be copied out without blocking.
74 are serialized to avoid deadlock.
76 The state is described using a ``Management Information Base'' (MIB)
81 length array of integers.
85 function accepts an ASCII representation of the name and internally
86 looks up the integer name vector. Apart from that, it behaves the same
91 The information is copied into the buffer specified by
93 The size of the buffer is given by the location specified by
96 and that location gives the amount of data copied after a successful call
97 and after a call that returns with the error code
99 If the amount of data available is greater
100 than the size of the buffer supplied,
101 the call supplies as much data as fits in the buffer provided
102 and returns with the error code
104 If the old value is not desired,
108 should be set to NULL.
110 The size of the available data can be determined by calling
112 with a NULL parameter for
114 The size of the available data will be returned in the location pointed to by
116 For some operations, the amount of space may change often.
117 For these operations,
118 the system attempts to round up so that the returned size is
119 large enough for a call to return the data shortly thereafter.
123 is set to point to a buffer of length
125 from which the requested value is to be taken.
126 If a new value is not to be set,
128 should be set to NULL and
134 function accepts an ASCII representation of the name,
135 looks up the integer name vector,
136 and returns the numeric representation in the mib array pointed to by
138 The number of elements in the mib array is given by the location specified by
141 and that location gives the number of entries copied after a successful call.
146 may be used in subsequent
148 calls to get the data associated with the requested ASCII name.
149 This interface is intended for use by applications that want to
150 repeatedly request the same variable (the
152 function runs in about a third the time as the same request made via the
157 function is also useful for fetching mib prefixes and then adding
159 For example, to fetch process information
160 for processes with pid's less than 100:
162 .Bd -literal -offset indent -compact
165 struct kinfo_proc kp;
167 /* Fill out the first three components of the mib */
169 sysctlnametomib("kern.proc.pid", mib, &len);
171 /* Fetch and print entries for pid's < 100 */
172 for (i = 0; i < 100; i++) {
175 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
182 The top level names are defined with a CTL_ prefix in
183 .Aq Pa sys/sysctl.h ,
185 The next and subsequent levels down are found in the include files
186 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"
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
312 The string and integer information available for the CTL_KERN level
314 The changeable column shows whether a process with appropriate
315 privilege may change the value.
316 The types of data currently available are process information,
317 system vnodes, the open file entries, routing table entries,
318 virtual memory statistics, load average history, and clock rate
320 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
321 .It Sy "Second level name Type Changeable"
322 .It "KERN\_ARGMAX integer no"
323 .It "KERN\_BOOTFILE string yes"
324 .It "KERN\_BOOTTIME struct timeval no"
325 .It "KERN\_CLOCKRATE struct clockinfo no"
326 .It "KERN\_FILE struct file no"
327 .It "KERN\_HOSTID integer yes"
328 .It "KERN\_HOSTNAME string yes"
329 .It "KERN\_JOB\_CONTROL integer no"
330 .It "KERN\_MAXFILES integer yes"
331 .It "KERN\_MAXFILESPERPROC integer yes"
332 .It "KERN\_MAXPROC integer no"
333 .It "KERN\_MAXPROCPERUID integer yes"
334 .It "KERN\_MAXVNODES integer yes"
335 .It "KERN\_NGROUPS integer no"
336 .It "KERN\_NISDOMAINNAME string yes"
337 .It "KERN\_OSRELDATE integer no"
338 .It "KERN\_OSRELEASE string no"
339 .It "KERN\_OSREV integer no"
340 .It "KERN\_OSTYPE string no"
341 .It "KERN\_POSIX1 integer no"
342 .It "KERN\_PROC struct proc no"
343 .It "KERN\_PROF node not applicable"
344 .It "KERN\_QUANTUM integer yes"
345 .It "KERN\_SAVED\_IDS integer no"
346 .It "KERN\_SECURELVL integer raise only"
347 .It "KERN\_UPDATEINTERVAL integer no"
348 .It "KERN\_VERSION string no"
349 .It "KERN\_VNODE struct vnode no"
354 The maximum bytes of argument to
357 The full pathname of the file from which the kernel was loaded.
361 structure is returned.
362 This structure contains the time that the system was booted.
363 .It Li KERN_CLOCKRATE
366 structure is returned.
367 This structure contains the clock, statistics clock and profiling clock
368 frequencies, the number of micro-seconds per hz tick and the skew rate.
370 Return the entire file table.
371 The returned data consists of a single
373 followed by an array of
375 whose size depends on the current number of such objects in the system.
377 Get or set the host id.
379 Get or set the hostname.
380 .It Li KERN_JOB_CONTROL
381 Return 1 if job control is available on this system, otherwise 0.
383 The maximum number of files that may be open in the system.
384 .It Li KERN_MAXFILESPERPROC
385 The maximum number of files that may be open for a single process.
386 This limit only applies to processes with an effective uid of nonzero
387 at the time of the open request.
388 Files that have already been opened are not affected if the limit
389 or the effective uid is changed.
391 The maximum number of concurrent processes the system will allow.
392 .It Li KERN_MAXPROCPERUID
393 The maximum number of concurrent processes the system will allow
394 for a single effective uid.
395 This limit only applies to processes with an effective uid of nonzero
396 at the time of a fork request.
397 Processes that have already been started are not affected if the limit
399 .It Li KERN_MAXVNODES
400 The maximum number of vnodes available on the system.
402 The maximum number of supplemental groups.
403 .It Li KERN_NISDOMAINNAME
404 The name of the current YP/NIS domain.
405 .It Li KERN_OSRELDATE
406 The system release date in YYYYMM format
407 (January 1996 is encoded as 199601).
408 .It Li KERN_OSRELEASE
409 The system release string.
411 The system revision string.
413 The system type string.
417 with which the system
420 Return the entire process table, or a subset of it.
422 .Va struct kinfo_proc
423 structures is returned,
424 whose size depends on the current number of such objects in the system.
425 The third and fourth level names are as follows:
426 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
427 .It "Third level name Fourth level is:"
428 .It "KERN\_PROC\_ALL None"
429 .It "KERN\_PROC\_PID A process ID"
430 .It "KERN\_PROC\_PGRP A process group"
431 .It "KERN\_PROC\_TTY A tty device"
432 .It "KERN\_PROC\_UID A user ID"
433 .It "KERN\_PROC\_RUID A real user ID"
436 Return profiling information about the kernel.
437 If the kernel is not compiled for profiling,
438 attempts to retrieve any of the KERN_PROF values will
441 The third level names for the string and integer profiling information
443 The changeable column shows whether a process with appropriate
444 privilege may change the value.
445 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
446 .It Sy "Third level name Type Changeable"
447 .It "GPROF\_STATE integer yes"
448 .It "GPROF\_COUNT u_short[\|] yes"
449 .It "GPROF\_FROMS u_short[\|] yes"
450 .It "GPROF\_TOS struct tostruct yes"
451 .It "GPROF\_GMONPARAM struct gmonparam no"
454 The variables are as follows:
457 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
458 is running or stopped.
460 Array of statistical program counter counts.
462 Array indexed by program counter of call-from points.
466 describing destination of calls and their counts.
467 .It Li GPROF_GMONPARAM
468 Structure giving the sizes of the above arrays.
471 The maximum period of time, in microseconds, for which a process is allowed
472 to run without being preempted if other processes are in the run queue.
473 .It Li KERN_SAVED_IDS
474 Returns 1 if saved set-group and saved set-user ID is available.
475 .It Li KERN_SECURELVL
476 The system security level.
477 This level may be raised by processes with appropriate privilege.
478 It may not be lowered.
480 The system version string.
482 Return the entire vnode table.
483 Note, the vnode table is not necessarily a consistent snapshot of
485 The returned data consists of an array whose size depends on the
486 current number of such objects in the system.
487 Each element of the array contains the kernel address of a vnode
489 followed by the vnode itself
493 The set of variables defined is architecture dependent.
494 The following variables are defined for the i386 architecture.
495 .Bl -column "CONSOLE_DEVICEXXX" "struct bootinfoXXX" -offset indent
496 .It Sy "Second level name Type Changeable"
497 .It Li "CPU_CONSDEV dev_t no"
498 .It Li "CPU_ADJKERNTZ int yes"
499 .It Li "CPU_DISRTCSET int yes"
500 .It Li "CPU_BOOTINFO struct bootinfo no"
501 .It Li "CPU_WALLCLOCK int yes"
504 The string and integer information available for the CTL_NET level
506 The changeable column shows whether a process with appropriate
507 privilege may change the value.
508 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
509 .It Sy "Second level name Type Changeable"
510 .It "PF\_ROUTE routing messages no"
511 .It "PF\_INET IPv4 values yes"
512 .It "PF\_INET6 IPv6 values yes"
517 Return the entire routing table or a subset of it.
518 The data is returned as a sequence of routing messages (see
520 for the header file, format and meaning).
521 The length of each message is contained in the message header.
523 The third level name is a protocol number, which is currently always 0.
524 The fourth level name is an address family, which may be set to 0 to
525 select all address families.
526 The fifth and sixth level names are as follows:
527 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
528 .It Sy "Fifth level name Sixth level is:"
529 .It "NET\_RT\_FLAGS rtflags"
530 .It "NET\_RT\_DUMP None"
531 .It "NET\_RT\_IFLIST None"
534 Get or set various global information about the IPv4
535 (Internet Protocol version 4).
536 The third level name is the protocol.
537 The fourth level name is the variable name.
538 The currently defined protocols and names are:
539 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
540 .It Sy "Protocol Variable Type Changeable"
541 .It "icmp bmcastecho integer yes"
542 .It "icmp maskrepl integer yes"
543 .It "ip forwarding integer yes"
544 .It "ip redirect integer yes"
545 .It "ip ttl integer yes"
546 .It "udp checksum integer yes"
549 The variables are as follows:
551 .It Li icmp.bmcastecho
552 Returns 1 if an ICMP echo request to a broadcast or multicast address is
555 Returns 1 if ICMP network mask requests are to be answered.
557 Returns 1 when IP forwarding is enabled for the host,
558 meaning that the host is acting as a router.
560 Returns 1 when ICMP redirects may be sent by the host.
561 This option is ignored unless the host is routing IP packets,
562 and should normally be enabled on all systems.
564 The maximum time-to-live (hop count) value for an IP packet sourced by
566 This value applies to normal transport protocols, not to ICMP.
568 Returns 1 when UDP checksums are being computed and checked.
569 Disabling UDP checksums is strongly discouraged.
571 For variables net.inet.*.ipsec, please refer to
575 Get or set various global information about the IPv6
576 (Internet Protocol version 6).
577 The third level name is the protocol.
578 The fourth level name is the variable name.
580 For variables net.inet6.* please refer to
582 For variables net.inet6.*.ipsec6, please refer to
586 The string and integer information available for the CTL_USER level
588 The changeable column shows whether a process with appropriate
589 privilege may change the value.
590 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
591 .It Sy "Second level name Type Changeable"
592 .It "USER\_BC\_BASE\_MAX integer no"
593 .It "USER\_BC\_DIM\_MAX integer no"
594 .It "USER\_BC\_SCALE\_MAX integer no"
595 .It "USER\_BC\_STRING\_MAX integer no"
596 .It "USER\_COLL\_WEIGHTS\_MAX integer no"
597 .It "USER\_CS\_PATH string no"
598 .It "USER\_EXPR\_NEST\_MAX integer no"
599 .It "USER\_LINE\_MAX integer no"
600 .It "USER\_POSIX2\_CHAR\_TERM integer no"
601 .It "USER\_POSIX2\_C\_BIND integer no"
602 .It "USER\_POSIX2\_C\_DEV integer no"
603 .It "USER\_POSIX2\_FORT\_DEV integer no"
604 .It "USER\_POSIX2\_FORT\_RUN integer no"
605 .It "USER\_POSIX2\_LOCALEDEF integer no"
606 .It "USER\_POSIX2\_SW\_DEV integer no"
607 .It "USER\_POSIX2\_UPE integer no"
608 .It "USER\_POSIX2\_VERSION integer no"
609 .It "USER\_RE\_DUP\_MAX integer no"
610 .It "USER\_STREAM\_MAX integer no"
611 .It "USER\_TZNAME\_MAX integer no"
615 .It Li USER_BC_BASE_MAX
616 The maximum ibase/obase values in the
619 .It Li USER_BC_DIM_MAX
620 The maximum array size in the
623 .It Li USER_BC_SCALE_MAX
624 The maximum scale value in the
627 .It Li USER_BC_STRING_MAX
628 The maximum string length in the
631 .It Li USER_COLL_WEIGHTS_MAX
632 The maximum number of weights that can be assigned to any entry of
633 the LC_COLLATE order keyword in the locale definition file.
635 Return a value for the
637 environment variable that finds all the standard utilities.
638 .It Li USER_EXPR_NEST_MAX
639 The maximum number of expressions that can be nested within
644 The maximum length in bytes of a text-processing utility's input
646 .It Li USER_POSIX2_CHAR_TERM
647 Return 1 if the system supports at least one terminal type capable of
648 all operations described in
651 .It Li USER_POSIX2_C_BIND
652 Return 1 if the system's C-language development facilities support the
653 C-Language Bindings Option, otherwise 0.
654 .It Li USER_POSIX2_C_DEV
655 Return 1 if the system supports the C-Language Development Utilities Option,
657 .It Li USER_POSIX2_FORT_DEV
658 Return 1 if the system supports the FORTRAN Development Utilities Option,
660 .It Li USER_POSIX2_FORT_RUN
661 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
663 .It Li USER_POSIX2_LOCALEDEF
664 Return 1 if the system supports the creation of locales, otherwise 0.
665 .It Li USER_POSIX2_SW_DEV
666 Return 1 if the system supports the Software Development Utilities Option,
668 .It Li USER_POSIX2_UPE
669 Return 1 if the system supports the User Portability Utilities Option,
671 .It Li USER_POSIX2_VERSION
674 with which the system attempts to comply.
675 .It Li USER_RE_DUP_MAX
676 The maximum number of repeated occurrences of a regular expression
677 permitted when using interval notation.
678 .It Li USER_STREAM_MAX
679 The minimum maximum number of streams that a process may have open
681 .It Li USER_TZNAME_MAX
682 The minimum maximum number of types supported for the name of a
686 The string and integer information available for the CTL_VM level
688 The changeable column shows whether a process with appropriate
689 privilege may change the value.
690 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
691 .It Sy "Second level name Type Changeable"
692 .It "VM\_LOADAVG struct loadavg no"
693 .It "VM\_METER struct vmtotal no"
694 .It "VM\_PAGEOUT\_ALGORITHM integer yes"
695 .It "VM\_SWAPPING\_ENABLED integer maybe"
696 .It "VM\_V\_CACHE\_MAX integer yes"
697 .It "VM\_V\_CACHE\_MIN integer yes"
698 .It "VM\_V\_FREE\_MIN integer yes"
699 .It "VM\_V\_FREE\_RESERVED integer yes"
700 .It "VM\_V\_FREE\_TARGET integer yes"
701 .It "VM\_V\_INACTIVE\_TARGET integer yes"
702 .It "VM\_V\_PAGEOUT\_FREE\_MIN integer yes"
707 Return the load average history.
708 The returned data consists of a
711 Return the system wide virtual memory statistics.
712 The returned data consists of a
714 .It Li VM_PAGEOUT_ALGORITHM
715 0 if the statistics-based page management algorithm is in use
716 or 1 if the near-LRU algorithm is in use.
717 .It Li VM_SWAPPING_ENABLED
718 1 if process swapping is enabled or 0 if disabled. This variable is
719 permanently set to 0 if the kernel was built with swapping disabled.
720 .It Li VM_V_CACHE_MAX
721 Maximum desired size of the cache queue.
722 .It Li VM_V_CACHE_MIN
723 Minimum desired size of the cache queue. If the cache queue size
724 falls very far below this value, the pageout daemon is awakened.
726 Minimum amount of memory (cache memory plus free memory)
727 required to be available before a process waiting on memory will be
729 .It Li VM_V_FREE_RESERVED
730 Processes will awaken the pageout daemon and wait for memory if the
731 number of free and cached pages drops below this value.
732 .It Li VM_V_FREE_TARGET
733 The total amount of free memory (including cache memory) that the
734 pageout daemon tries to maintain.
735 .It Li VM_V_INACTIVE_TARGET
736 The desired number of inactive pages that the pageout daemon should
737 achieve when it runs. Inactive pages can be quickly inserted into
738 process address space when needed.
739 .It Li VM_V_PAGEOUT_FREE_MIN
740 If the amount of free and cache memory falls below this value, the
741 pageout daemon will enter "memory conserving mode" to avoid deadlock.
746 The following errors may be reported:
755 contains an invalid address.
759 array is less than two or greater than CTL_MAXNAME.
763 is given and its specified length in
765 is too large or too small.
767 The length pointed to by
769 is too short to hold the requested value.
773 array specifies an intermediate rather than terminal name.
777 array specifies a terminal name, but the actual name is not terminal.
781 array specifies a value that is unknown.
783 An attempt is made to set a read-only value.
785 A process without appropriate privilege attempts to set a value.
788 .Bl -tag -width <netinet/icmpXvar.h> -compact
789 .It Aq Pa sys/sysctl.h
790 definitions for top level identifiers, second level kernel and hardware
791 identifiers, and user level identifiers
792 .It Aq Pa sys/socket.h
793 definitions for second level network identifiers
795 definitions for third level profiling identifiers
796 .It Aq Pa vm/vm_param.h
797 definitions for second level virtual memory identifiers
798 .It Aq Pa netinet/in.h
799 definitions for third level IPv4/IPv6 identifiers and
800 fourth level IPv4/v6 identifiers
801 .It Aq Pa netinet/icmp_var.h
802 definitions for fourth level ICMP identifiers
803 .It Aq Pa netinet/icmp6.h
804 definitions for fourth level ICMPv6 identifiers
805 .It Aq Pa netinet/udp_var.h
806 definitions for fourth level UDP identifiers
814 function first appeared in