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28 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
37 .Nd get or set system information
43 .Fn sysctl "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
45 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
47 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
51 function retrieves system information and allows processes with
52 appropriate privileges to set system information.
53 The information available from
55 consists of integers, strings, and tables.
56 Information may be retrieved and set from the command interface
61 Unless explicitly noted below,
63 returns a consistent snapshot of the data requested.
64 Consistency is obtained by locking the destination
65 buffer into memory so that the data may be copied out without blocking.
68 are serialized to avoid deadlock.
70 The state is described using a ``Management Information Base'' (MIB)
75 length array of integers.
79 function accepts an ASCII representation of the name and internally
80 looks up the integer name vector.
81 Apart from that, it behaves the same
86 The information is copied into the buffer specified by
88 The size of the buffer is given by the location specified by
91 and that location gives the amount of data copied after a successful call
92 and after a call that returns with the error code
94 If the amount of data available is greater
95 than the size of the buffer supplied,
96 the call supplies as much data as fits in the buffer provided
97 and returns with the error code
99 If the old value is not desired,
103 should be set to NULL.
105 The size of the available data can be determined by calling
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 Ta Sy Next Level Names Ta Sy Description
186 .It Dv CTL_DEBUG Ta In sys/sysctl.h Ta Debugging
187 .It Dv CTL_VFS Ta In sys/mount.h Ta File system
188 .It Dv CTL_HW Ta In sys/sysctl.h Ta Generic CPU, I/O
189 .It Dv CTL_KERN Ta In sys/sysctl.h Ta High kernel limits
190 .It Dv CTL_MACHDEP Ta In sys/sysctl.h Ta Machine dependent
191 .It Dv CTL_NET Ta In sys/socket.h Ta Networking
192 .It Dv CTL_USER Ta In sys/sysctl.h Ta User-level
193 .It Dv CTL_VM Ta In vm/vm_param.h Ta 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 .Pq Vt "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:
245 .Bd -literal -offset indent -compact
246 int dospecialcheck = 1;
247 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
250 A distinguished second level name, VFS_GENERIC,
251 is used to get general information about all file systems.
252 One of its third level identifiers is VFS_MAXTYPENUM
253 that gives the highest valid file system type number.
254 Its other third level identifier is VFS_CONF that
255 returns configuration information about the file system
256 type given as a fourth level identifier (see
258 as an example of its use).
259 The remaining second level identifiers are the
260 file system type number returned by a
262 call or from VFS_CONF.
263 The third level identifiers available for each file system
264 are given in the header file that defines the mount
265 argument structure for that file system.
267 The string and integer information available for the CTL_HW level
269 The changeable column shows whether a process with appropriate
270 privilege may change the value.
271 .Bl -column "Second Level Name" integerXXX Changeable -offset indent
272 .It Sy Second Level Name Ta Sy Type Ta Sy Changeable
273 .It Dv HW_MACHINE Ta string Ta no
274 .It Dv HW_MODEL Ta string Ta no
275 .It Dv HW_NCPU Ta integer Ta no
276 .It Dv HW_BYTEORDER Ta integer Ta no
277 .It Dv HW_PHYSMEM Ta integer Ta no
278 .It Dv HW_USERMEM Ta integer Ta no
279 .It Dv HW_PAGESIZE Ta integer Ta no
280 .\".It Dv HW_DISKNAMES Ta integer Ta no
281 .\".It Dv HW_DISKSTATS Ta integer Ta no
282 .It Dv HW_FLOATINGPT Ta integer Ta no
283 .It Dv HW_MACHINE_ARCH Ta string Ta no
284 .It Dv HW_REALMEM Ta integer Ta no
285 .It Dv HW_AVAILPAGES Ta integer Ta no
295 The byteorder (4321 or 1234).
297 Amount of physical memory (in bytes), minus the amount used by the kernel,
298 pre-loaded modules, and (on x86) the dcons buffer.
300 Amount of memory (in bytes) which is not wired.
302 The software page size.
303 .\".It Fa HW_DISKNAMES
304 .\".It Fa HW_DISKSTATS
306 Nonzero if the floating point support is in hardware.
307 .It Li HW_MACHINE_ARCH
308 The machine dependent architecture type.
310 Amount of memory (in bytes) reported by the firmware.
311 That value is sometimes not sane; in that case, the kernel reports the max
312 memory address instead.
316 measured in pages rather than bytes.
319 The string and integer information available for the CTL_KERN level
321 The changeable column shows whether a process with appropriate
322 privilege may change the value.
323 The types of data currently available are process information,
324 system vnodes, the open file entries, routing table entries,
325 virtual memory statistics, load average history, and clock rate
327 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
328 .It Sy Second Level Name Ta Sy Type Ta Sy Changeable
329 .It Dv KERN_ARGMAX Ta integer Ta no
330 .It Dv KERN_BOOTFILE Ta string Ta yes
331 .It Dv KERN_BOOTTIME Ta struct timeval Ta no
332 .It Dv KERN_CLOCKRATE Ta struct clockinfo Ta no
333 .It Dv KERN_FILE Ta struct xfile Ta no
334 .It Dv KERN_HOSTID Ta integer Ta yes
335 .It Dv KERN_HOSTUUID Ta string Ta yes
336 .It Dv KERN_HOSTNAME Ta string Ta yes
337 .It Dv KERN_JOB_CONTROL Ta integer Ta no
338 .It Dv KERN_MAXFILES Ta integer Ta yes
339 .It Dv KERN_MAXFILESPERPROC Ta integer Ta yes
340 .It Dv KERN_MAXPROC Ta integer Ta no
341 .It Dv KERN_MAXPROCPERUID Ta integer Ta yes
342 .It Dv KERN_MAXVNODES Ta integer Ta yes
343 .It Dv KERN_NGROUPS Ta integer Ta no
344 .It Dv KERN_NISDOMAINNAME Ta string Ta yes
345 .It Dv KERN_OSRELDATE Ta integer Ta no
346 .It Dv KERN_OSRELEASE Ta string Ta no
347 .It Dv KERN_OSREV Ta integer Ta no
348 .It Dv KERN_OSTYPE Ta string Ta no
349 .It Dv KERN_POSIX1 Ta integer Ta no
350 .It Dv KERN_PROC Ta node Ta not applicable
351 .It Dv KERN_QUANTUM Ta integer Ta yes
352 .It Dv KERN_SAVED_IDS Ta integer Ta no
353 .It Dv KERN_SECURELVL Ta integer Ta raise only
354 .It Dv KERN_UPDATEINTERVAL Ta integer Ta no
355 .It Dv KERN_VERSION Ta string Ta no
359 The maximum bytes of argument to
362 The full pathname of the file from which the kernel was loaded.
366 structure is returned.
367 This structure contains the time that the system was booted.
368 .It Li KERN_CLOCKRATE
371 structure is returned.
372 This structure contains the clock, statistics clock and profiling clock
373 frequencies, the number of micro-seconds per hz tick and the skew rate.
375 Return the entire file table.
376 The returned data consists of an array of
378 whose size depends on the current number of such objects in the system.
380 Get or set the host ID.
382 Get or set the host's universally unique identifier (UUID).
384 Get or set the hostname.
385 .It Li KERN_JOB_CONTROL
386 Return 1 if job control is available on this system, otherwise 0.
388 The maximum number of files that may be open in the system.
389 .It Li KERN_MAXFILESPERPROC
390 The maximum number of files that may be open for a single process.
391 This limit only applies to processes with an effective uid of nonzero
392 at the time of the open request.
393 Files that have already been opened are not affected if the limit
394 or the effective uid is changed.
396 The maximum number of concurrent processes the system will allow.
397 .It Li KERN_MAXPROCPERUID
398 The maximum number of concurrent processes the system will allow
399 for a single effective uid.
400 This limit only applies to processes with an effective uid of nonzero
401 at the time of a fork request.
402 Processes that have already been started are not affected if the limit
404 .It Li KERN_MAXVNODES
405 The maximum number of vnodes available on the system.
407 The maximum number of supplemental groups.
408 .It Li KERN_NISDOMAINNAME
409 The name of the current YP/NIS domain.
410 .It Li KERN_OSRELDATE
411 The kernel release version in the format
412 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
415 is the major version,
417 is the two digit minor version,
419 is 0 if release branch, otherwise 1,
422 is updated when the available APIs change.
424 The userland release version is available from
426 parse this file if you need to get the release version of
427 the currently installed userland.
428 .It Li KERN_OSRELEASE
429 The system release string.
431 The system revision string.
433 The system type string.
437 with which the system
440 Return selected information about specific running processes.
442 For the following names, an array of
443 .Va struct kinfo_proc
444 structures is returned,
445 whose size depends on the current number of such objects in the system.
446 .Bl -column "Third Level NameXXXXXX" "Fourth LevelXXXXXX" -offset indent
447 .It Sy Third Level Name Ta Sy Fourth Level
448 .It Dv KERN_PROC_ALL Ta None
449 .It Dv KERN_PROC_PID Ta A process ID
450 .It Dv KERN_PROC_PGRP Ta A process group
451 .It Dv KERN_PROC_TTY Ta A tty device
452 .It Dv KERN_PROC_UID Ta A user ID
453 .It Dv KERN_PROC_RUID Ta A real user ID
456 If the third level name is
458 then the command line argument
459 array is returned in a flattened form, i.e., zero-terminated arguments
461 The total size of array is returned.
462 It is also possible for a process to set its own process title this way.
463 If the third level name is
464 .Dv KERN_PROC_PATHNAME ,
466 process' text file is stored.
468 .Dv KERN_PROC_PATHNAME ,
471 implies the current process.
472 .Bl -column "Third Level NameXXXXXX" "Fourth LevelXXXXXX" -offset indent
473 .It Sy Third Level Name Ta Sy Fourth Level
474 .It Dv KERN_PROC_ARGS Ta "A process ID"
475 .It Dv KERN_PROC_PATHNAME Ta "A process ID"
478 The maximum period of time, in microseconds, for which a process is allowed
479 to run without being preempted if other processes are in the run queue.
480 .It Li KERN_SAVED_IDS
481 Returns 1 if saved set-group and saved set-user ID is available.
482 .It Li KERN_SECURELVL
483 The system security level.
484 This level may be raised by processes with appropriate privilege.
485 It may not be lowered.
487 The system version string.
490 The string and integer information available for the CTL_NET level
492 The changeable column shows whether a process with appropriate
493 privilege may change the value.
494 .Bl -column "Second Level NameXXXXXX" "routing messagesXXX" -offset indent
495 .It Sy Second Level Name Ta Sy Type Ta Sy Changeable
496 .It Dv PF_ROUTE Ta routing messages Ta no
497 .It Dv PF_INET Ta IPv4 values Ta yes
498 .It Dv PF_INET6 Ta IPv6 values Ta yes
502 Return the entire routing table or a subset of it.
503 The data is returned as a sequence of routing messages (see
505 for the header file, format and meaning).
506 The length of each message is contained in the message header.
508 The third level name is a protocol number, which is currently always 0.
509 The fourth level name is an address family, which may be set to 0 to
510 select all address families.
511 The fifth, sixth, and seventh level names are as follows:
512 .Bl -column -offset indent "Fifth Level" "Sixth Level" "Seventh Level"
513 .It Sy Fifth level Ta Sy Sixth Level Ta Sy Seventh Level
514 .It Dv NET_RT_FLAGS Ta rtflags Ta None
515 .It Dv NET_RT_DUMP Ta None Ta None or fib number
516 .It Dv NET_RT_IFLIST Ta 0 or if_index Ta None
517 .It Dv NET_RT_IFMALIST Ta 0 or if_index Ta None
518 .It Dv NET_RT_IFLISTL Ta 0 or if_index Ta None
519 .It Dv NET_RT_NHOPS Ta None Ta fib number
524 name returns information about multicast group memberships on all interfaces
525 if 0 is specified, or for the interface specified by
532 just returning message header structs with additional fields allowing the
533 interface to be extended without breaking binary compatibility.
536 uses 'l' versions of the message header structures:
537 .Va struct if_msghdrl
539 .Va struct ifa_msghdrl .
542 returns all nexthops for specified address family in given fib.
544 Get or set various global information about the IPv4
545 (Internet Protocol version 4).
546 The third level name is the protocol.
547 The fourth level name is the variable name.
548 The currently defined protocols and names are:
549 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
550 .It Sy Protocol Ta Sy Variable Ta Sy Type Ta Sy Changeable
551 .It icmp Ta bmcastecho Ta integer Ta yes
552 .It icmp Ta maskrepl Ta integer Ta yes
553 .It ip Ta forwarding Ta integer Ta yes
554 .It ip Ta redirect Ta integer Ta yes
555 .It ip Ta ttl Ta integer Ta yes
556 .It udp Ta checksum Ta integer Ta yes
559 The variables are as follows:
561 .It Li icmp.bmcastecho
562 Returns 1 if an ICMP echo request to a broadcast or multicast address is
565 Returns 1 if ICMP network mask requests are to be answered.
567 Returns 1 when IP forwarding is enabled for the host,
568 meaning that the host is acting as a router.
570 Returns 1 when ICMP redirects may be sent by the host.
571 This option is ignored unless the host is routing IP packets,
572 and should normally be enabled on all systems.
574 The maximum time-to-live (hop count) value for an IP packet sourced by
576 This value applies to normal transport protocols, not to ICMP.
578 Returns 1 when UDP checksums are being computed and checked.
579 Disabling UDP checksums is strongly discouraged.
581 For variables net.inet.*.ipsec, please refer to
585 Get or set various global information about the IPv6
586 (Internet Protocol version 6).
587 The third level name is the protocol.
588 The fourth level name is the variable name.
590 For variables net.inet6.* please refer to
592 For variables net.inet6.*.ipsec6, please refer to
596 The string and integer information available for the CTL_USER level
598 The changeable column shows whether a process with appropriate
599 privilege may change the value.
600 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
601 .It Sy Second Level Name Ta Sy Type Ta Sy Changeable
602 .It Dv USER_BC_BASE_MAX Ta integer Ta no
603 .It Dv USER_BC_DIM_MAX Ta integer Ta no
604 .It Dv USER_BC_SCALE_MAX Ta integer Ta no
605 .It Dv USER_BC_STRING_MAX Ta integer Ta no
606 .It Dv USER_COLL_WEIGHTS_MAX Ta integer Ta no
607 .It Dv USER_CS_PATH Ta string Ta no
608 .It Dv USER_EXPR_NEST_MAX Ta integer Ta no
609 .It Dv USER_LINE_MAX Ta integer Ta no
610 .It Dv USER_LOCALBASE Ta string Ta no
611 .It Dv USER_POSIX2_CHAR_TERM Ta integer Ta no
612 .It Dv USER_POSIX2_C_BIND Ta integer Ta no
613 .It Dv USER_POSIX2_C_DEV Ta integer Ta no
614 .It Dv USER_POSIX2_FORT_DEV Ta integer Ta no
615 .It Dv USER_POSIX2_FORT_RUN Ta integer Ta no
616 .It Dv USER_POSIX2_LOCALEDEF Ta integer Ta no
617 .It Dv USER_POSIX2_SW_DEV Ta integer Ta no
618 .It Dv USER_POSIX2_UPE Ta integer Ta no
619 .It Dv USER_POSIX2_VERSION Ta integer Ta no
620 .It Dv USER_RE_DUP_MAX Ta integer Ta no
621 .It Dv USER_STREAM_MAX Ta integer Ta no
622 .It Dv USER_TZNAME_MAX Ta integer Ta no
625 .It Li USER_BC_BASE_MAX
626 The maximum ibase/obase values in the
629 .It Li USER_BC_DIM_MAX
630 The maximum array size in the
633 .It Li USER_BC_SCALE_MAX
634 The maximum scale value in the
637 .It Li USER_BC_STRING_MAX
638 The maximum string length in the
641 .It Li USER_COLL_WEIGHTS_MAX
642 The maximum number of weights that can be assigned to any entry of
643 the LC_COLLATE order keyword in the locale definition file.
645 Return a value for the
647 environment variable that finds all the standard utilities.
648 .It Li USER_EXPR_NEST_MAX
649 The maximum number of expressions that can be nested within
654 The maximum length in bytes of a text-processing utility's input
656 .It Li USER_LOCALBASE
657 Return the value of localbase that has been compiled into system utilities
658 that need to have access to resources provided by a port or package.
659 .It Li USER_POSIX2_CHAR_TERM
660 Return 1 if the system supports at least one terminal type capable of
661 all operations described in
664 .It Li USER_POSIX2_C_BIND
665 Return 1 if the system's C-language development facilities support the
666 C-Language Bindings Option, otherwise 0.
667 .It Li USER_POSIX2_C_DEV
668 Return 1 if the system supports the C-Language Development Utilities Option,
670 .It Li USER_POSIX2_FORT_DEV
671 Return 1 if the system supports the FORTRAN Development Utilities Option,
673 .It Li USER_POSIX2_FORT_RUN
674 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
676 .It Li USER_POSIX2_LOCALEDEF
677 Return 1 if the system supports the creation of locales, otherwise 0.
678 .It Li USER_POSIX2_SW_DEV
679 Return 1 if the system supports the Software Development Utilities Option,
681 .It Li USER_POSIX2_UPE
682 Return 1 if the system supports the User Portability Utilities Option,
684 .It Li USER_POSIX2_VERSION
687 with which the system attempts to comply.
688 .It Li USER_RE_DUP_MAX
689 The maximum number of repeated occurrences of a regular expression
690 permitted when using interval notation.
691 .It Li USER_STREAM_MAX
692 The minimum maximum number of streams that a process may have open
694 .It Li USER_TZNAME_MAX
695 The minimum maximum number of types supported for the name of a
699 The string and integer information available for the CTL_VM level
701 The changeable column shows whether a process with appropriate
702 privilege may change the value.
703 .Bl -column "Second Level NameXXXXXX" "struct loadavgXXX" -offset indent
704 .It Sy Second Level Name Ta Sy Type Ta Sy Changeable
705 .It Dv VM_LOADAVG Ta struct loadavg Ta no
706 .It Dv VM_TOTAL Ta struct vmtotal Ta no
707 .It Dv VM_SWAPPING_ENABLED Ta integer Ta maybe
708 .It Dv VM_V_FREE_MIN Ta integer Ta yes
709 .It Dv VM_V_FREE_RESERVED Ta integer Ta yes
710 .It Dv VM_V_FREE_TARGET Ta integer Ta yes
711 .It Dv VM_V_INACTIVE_TARGET Ta integer Ta yes
712 .It Dv VM_V_PAGEOUT_FREE_MIN Ta integer Ta yes
713 .It Dv VM_OVERCOMMIT Ta integer Ta yes
717 Return the load average history.
718 The returned data consists of a
721 Return the system wide virtual memory statistics.
722 The returned data consists of a
724 .It Li VM_SWAPPING_ENABLED
725 1 if process swapping is enabled or 0 if disabled.
727 permanently set to 0 if the kernel was built with swapping disabled.
729 Minimum amount of memory (cache memory plus free memory)
730 required to be available before a process waiting on memory will be
732 .It Li VM_V_FREE_RESERVED
733 Processes will awaken the pageout daemon and wait for memory if the
734 number of free and cached pages drops below this value.
735 .It Li VM_V_FREE_TARGET
736 The total amount of free memory (including cache memory) that the
737 pageout daemon tries to maintain.
738 .It Li VM_V_INACTIVE_TARGET
739 The desired number of inactive pages that the pageout daemon should
740 achieve when it runs.
741 Inactive pages can be quickly inserted into
742 process address space when needed.
743 .It Li VM_V_PAGEOUT_FREE_MIN
744 If the amount of free and cache memory falls below this value, the
745 pageout daemon will enter "memory conserving mode" to avoid deadlock.
747 Overcommit behaviour, as described in
753 .Bl -tag -width <netinet/icmpXvar.h> -compact
755 definitions for top level identifiers, second level kernel and hardware
756 identifiers, and user level identifiers
758 definitions for second level network identifiers
760 definitions for third level profiling identifiers
762 definitions for second level virtual memory identifiers
764 definitions for third level IPv4/IPv6 identifiers and
765 fourth level IPv4/v6 identifiers
766 .It In netinet/icmp_var.h
767 definitions for fourth level ICMP identifiers
768 .It In netinet/icmp6.h
769 definitions for fourth level ICMPv6 identifiers
770 .It In netinet/udp_var.h
771 definitions for fourth level UDP identifiers
774 The following errors may be reported:
783 contains an invalid address.
787 array is less than two or greater than CTL_MAXNAME.
791 is given and its specified length in
793 is too large or too small.
795 The length pointed to by
797 is too short to hold the requested value.
799 The smaller of either the length pointed to by
801 or the estimated size of the returned data exceeds the
802 system limit on locked memory.
806 or a portion of the buffer if the estimated size of the data
807 to be returned is smaller,
808 would cause the process to exceed its per-process locked memory limit.
812 array specifies an intermediate rather than terminal name.
816 array specifies a terminal name, but the actual name is not terminal.
820 array specifies a value that is unknown.
822 An attempt is made to set a read-only value.
824 A process without appropriate privilege attempts to set a value.
834 function first appeared in