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28 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
38 .Nd get or set system information
45 .Fn sysctl "const int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
47 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "const void *newp" "size_t newlen"
49 .Fn sysctlnametomib "const char *name" "int *mibp" "size_t *sizep"
53 function retrieves system information and allows processes with
54 appropriate privileges to set system information.
55 The information available from
57 consists of integers, strings, and tables.
58 Information may be retrieved and set from the command interface
63 Unless explicitly noted below,
65 returns a consistent snapshot of the data requested.
66 Consistency is obtained by locking the destination
67 buffer into memory so that the data may be copied out without blocking.
70 are serialized to avoid deadlock.
72 The state is described using a ``Management Information Base'' (MIB)
77 length array of integers.
81 function accepts an ASCII representation of the name and internally
82 looks up the integer name vector.
83 Apart from that, it behaves the same
88 The information is copied into the buffer specified by
90 The size of the buffer is given by the location specified by
93 and that location gives the amount of data copied after a successful call
94 and after a call that returns with the error code
96 If the amount of data available is greater
97 than the size of the buffer supplied,
98 the call supplies as much data as fits in the buffer provided
99 and returns with the error code
101 If the old value is not desired,
105 should be set to NULL.
107 The size of the available data can be determined by calling
113 The size of the available data will be returned in the location pointed to by
115 For some operations, the amount of space may change often.
116 For these operations,
117 the system attempts to round up so that the returned size is
118 large enough for a call to return the data shortly thereafter.
122 is set to point to a buffer of length
124 from which the requested value is to be taken.
125 If a new value is not to be set,
127 should be set to NULL and
133 function accepts an ASCII representation of the name,
134 looks up the integer name vector,
135 and returns the numeric representation in the mib array pointed to by
137 The number of elements in the mib array is given by the location specified by
140 and that location gives the number of entries copied after a successful call.
145 may be used in subsequent
147 calls to get the data associated with the requested ASCII name.
148 This interface is intended for use by applications that want to
149 repeatedly request the same variable (the
151 function runs in about a third the time as the same request made via the
156 function is also useful for fetching mib prefixes and then adding
158 For example, to fetch process information
159 for processes with pid's less than 100:
161 .Bd -literal -offset indent -compact
164 struct kinfo_proc kp;
166 /* Fill out the first three components of the mib */
168 sysctlnametomib("kern.proc.pid", mib, &len);
170 /* Fetch and print entries for pid's < 100 */
171 for (i = 0; i < 100; i++) {
174 if (sysctl(mib, 4, &kp, &len, NULL, 0) == -1)
181 The top level names are defined with a CTL_ prefix in
184 The next and subsequent levels down are found in the include files
185 listed here, and described in separate sections below.
186 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
187 .It Sy "Name Next level names Description"
188 .It "CTL_DEBUG sys/sysctl.h Debugging"
189 .It "CTL_VFS sys/mount.h File system"
190 .It "CTL_HW sys/sysctl.h Generic CPU, I/O"
191 .It "CTL_KERN sys/sysctl.h High kernel limits"
192 .It "CTL_MACHDEP sys/sysctl.h Machine dependent"
193 .It "CTL_NET sys/socket.h Networking"
194 .It "CTL_USER sys/sysctl.h User-level"
195 .It "CTL_VM vm/vm_param.h Virtual memory"
198 For example, the following retrieves the maximum number of processes allowed
201 .Bd -literal -offset indent -compact
206 mib[1] = KERN_MAXPROC;
207 len = sizeof(maxproc);
208 sysctl(mib, 2, &maxproc, &len, NULL, 0);
211 To retrieve the standard search path for the system utilities:
213 .Bd -literal -offset indent -compact
219 mib[1] = USER_CS_PATH;
220 sysctl(mib, 2, NULL, &len, NULL, 0);
222 sysctl(mib, 2, p, &len, NULL, 0);
225 The debugging variables vary from system to system.
226 A debugging variable may be added or deleted without need to recompile
231 gets the list of debugging variables from the kernel and
232 displays their current values.
233 The system defines twenty
234 .Pq Vt "struct ctldebug"
239 They are declared as separate variables so that they can be
240 individually initialized at the location of their associated variable.
241 The loader prevents multiple use of the same variable by issuing errors
242 if a variable is initialized in more than one place.
243 For example, to export the variable
245 as a debugging variable, the following declaration would be used:
247 .Bd -literal -offset indent -compact
248 int dospecialcheck = 1;
249 struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
252 A distinguished second level name, VFS_GENERIC,
253 is used to get general information about all file systems.
254 One of its third level identifiers is VFS_MAXTYPENUM
255 that gives the highest valid file system type number.
256 Its other third level identifier is VFS_CONF that
257 returns configuration information about the file system
258 type given as a fourth level identifier (see
260 as an example of its use).
261 The remaining second level identifiers are the
262 file system type number returned by a
264 call or from VFS_CONF.
265 The third level identifiers available for each file system
266 are given in the header file that defines the mount
267 argument structure for that file system.
269 The string and integer information available for the CTL_HW level
271 The changeable column shows whether a process with appropriate
272 privilege may change the value.
273 .Bl -column "Second level nameXXXXXX" integerXXX -offset indent
274 .It Sy "Second level name Type Changeable"
275 .It "HW_MACHINE string no"
276 .It "HW_MODEL string no"
277 .It "HW_NCPU integer no"
278 .It "HW_BYTEORDER integer no"
279 .It "HW_PHYSMEM integer no"
280 .It "HW_USERMEM integer no"
281 .It "HW_PAGESIZE integer no"
282 .\".It "HW_DISKNAMES integer no"
283 .\".It "HW_DISKSTATS integer no"
284 .It "HW_FLOATINGPT integer no"
285 .It "HW_MACHINE_ARCH string no"
286 .It "HW_REALMEM integer no"
296 The byteorder (4,321, or 1,234).
298 The bytes of physical memory.
300 The bytes of non-kernel memory.
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 The bytes of real memory.
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 "KERNXMAXFILESPERPROCXXX" "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 xfile no"
328 .It "KERN_HOSTID integer yes"
329 .It "KERN_HOSTUUID string yes"
330 .It "KERN_HOSTNAME string yes"
331 .It "KERN_JOB_CONTROL integer no"
332 .It "KERN_MAXFILES integer yes"
333 .It "KERN_MAXFILESPERPROC 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 node not applicable"
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 xvnode no"
355 The maximum bytes of argument to
358 The full pathname of the file from which the kernel was loaded.
362 structure is returned.
363 This structure contains the time that the system was booted.
364 .It Li KERN_CLOCKRATE
367 structure is returned.
368 This structure contains the clock, statistics clock and profiling clock
369 frequencies, the number of micro-seconds per hz tick and the skew rate.
371 Return the entire file table.
372 The returned data consists of an array of
374 whose size depends on the current number of such objects in the system.
376 Get or set the host ID.
378 Get or set the host's universally unique identifier (UUID).
380 Get or set the hostname.
381 .It Li KERN_JOB_CONTROL
382 Return 1 if job control is available on this system, otherwise 0.
384 The maximum number of files that may be open in the system.
385 .It Li KERN_MAXFILESPERPROC
386 The maximum number of files that may be open for a single process.
387 This limit only applies to processes with an effective uid of nonzero
388 at the time of the open request.
389 Files that have already been opened are not affected if the limit
390 or the effective uid is changed.
392 The maximum number of concurrent processes the system will allow.
393 .It Li KERN_MAXPROCPERUID
394 The maximum number of concurrent processes the system will allow
395 for a single effective uid.
396 This limit only applies to processes with an effective uid of nonzero
397 at the time of a fork request.
398 Processes that have already been started are not affected if the limit
400 .It Li KERN_MAXVNODES
401 The maximum number of vnodes available on the system.
403 The maximum number of supplemental groups.
404 .It Li KERN_NISDOMAINNAME
405 The name of the current YP/NIS domain.
406 .It Li KERN_OSRELDATE
407 The kernel release version in the format
408 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
411 is the major version,
413 is the two digit minor version,
415 is 0 if release branch, otherwise 1,
418 is updated when the available APIs change.
420 The userland release version is available from
422 parse this file if you need to get the release version of
423 the currently installed userland.
424 .It Li KERN_OSRELEASE
425 The system release string.
427 The system revision string.
429 The system type string.
433 with which the system
436 Return selected information about specific running processes.
438 For the following names, an array of
439 .Va struct kinfo_proc
440 structures is returned,
441 whose size depends on the current number of such objects in the system.
442 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
443 .It "Third level name Fourth level is:"
444 .It "KERN_PROC_ALL None"
445 .It "KERN_PROC_PID A process ID"
446 .It "KERN_PROC_PGRP A process group"
447 .It "KERN_PROC_TTY A tty device"
448 .It "KERN_PROC_UID A user ID"
449 .It "KERN_PROC_RUID A real user ID"
452 If the third level name is
454 then the command line argument
455 array is returned in a flattened form, i.e., zero-terminated arguments
457 The total size of array is returned.
458 It is also possible for a process to set its own process title this way.
459 If the third level name is
460 .Dv KERN_PROC_PATHNAME ,
462 process' text file is stored.
464 .Dv KERN_PROC_PATHNAME ,
467 implies the current process.
468 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
469 .It Sy "Third level name Fourth level is:"
470 .It Dv KERN_PROC_ARGS Ta "A process ID"
471 .It Dv KERN_PROC_PATHNAME Ta "A process ID"
474 Return profiling information about the kernel.
475 If the kernel is not compiled for profiling,
476 attempts to retrieve any of the KERN_PROF values will
479 The third level names for the string and integer profiling information
481 The changeable column shows whether a process with appropriate
482 privilege may change the value.
483 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
484 .It Sy "Third level name Type Changeable"
485 .It "GPROF_STATE integer yes"
486 .It "GPROF_COUNT u_short[\|] yes"
487 .It "GPROF_FROMS u_short[\|] yes"
488 .It "GPROF_TOS struct tostruct yes"
489 .It "GPROF_GMONPARAM struct gmonparam no"
492 The variables are as follows:
495 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
496 is running or stopped.
498 Array of statistical program counter counts.
500 Array indexed by program counter of call-from points.
504 describing destination of calls and their counts.
505 .It Li GPROF_GMONPARAM
506 Structure giving the sizes of the above arrays.
509 The maximum period of time, in microseconds, for which a process is allowed
510 to run without being preempted if other processes are in the run queue.
511 .It Li KERN_SAVED_IDS
512 Returns 1 if saved set-group and saved set-user ID is available.
513 .It Li KERN_SECURELVL
514 The system security level.
515 This level may be raised by processes with appropriate privilege.
516 It may not be lowered.
518 The system version string.
520 Return the entire vnode table.
521 Note, the vnode table is not necessarily a consistent snapshot of
523 The returned data consists of an array whose size depends on the
524 current number of such objects in the system.
525 Each element of the array consists of a
529 The string and integer information available for the CTL_NET level
531 The changeable column shows whether a process with appropriate
532 privilege may change the value.
533 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
534 .It Sy "Second level name Type Changeable"
535 .It "PF_ROUTE routing messages no"
536 .It "PF_INET IPv4 values yes"
537 .It "PF_INET6 IPv6 values yes"
541 Return the entire routing table or a subset of it.
542 The data is returned as a sequence of routing messages (see
544 for the header file, format and meaning).
545 The length of each message is contained in the message header.
547 The third level name is a protocol number, which is currently always 0.
548 The fourth level name is an address family, which may be set to 0 to
549 select all address families.
550 The fifth, sixth, and seventh level names are as follows:
551 .Bl -column -offset indent "Fifth level Sixth level" "Seventh level"
552 .It Sy "Fifth level Sixth level" Ta Sy "Seventh level"
553 .It "NET_RT_FLAGS rtflags" Ta "None"
554 .It "NET_RT_DUMP None" Ta "None or fib number"
555 .It "NET_RT_IFLIST 0 or if_index" Ta None
556 .It "NET_RT_IFMALIST 0 or if_index" Ta None
557 .It "NET_RT_IFLISTL 0 or if_index" Ta None
562 name returns information about multicast group memberships on all interfaces
563 if 0 is specified, or for the interface specified by
570 just returning message header structs with additional fields allowing the
571 interface to be extended without breaking binary compatibility.
574 uses 'l' versions of the message header structures:
575 .Va struct if_msghdrl
577 .Va struct ifa_msghdrl .
579 Get or set various global information about the IPv4
580 (Internet Protocol version 4).
581 The third level name is the protocol.
582 The fourth level name is the variable name.
583 The currently defined protocols and names are:
584 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
585 .It Sy "Protocol Variable Type Changeable"
586 .It "icmp bmcastecho integer yes"
587 .It "icmp maskrepl integer yes"
588 .It "ip forwarding integer yes"
589 .It "ip redirect integer yes"
590 .It "ip ttl integer yes"
591 .It "udp checksum integer yes"
594 The variables are as follows:
596 .It Li icmp.bmcastecho
597 Returns 1 if an ICMP echo request to a broadcast or multicast address is
600 Returns 1 if ICMP network mask requests are to be answered.
602 Returns 1 when IP forwarding is enabled for the host,
603 meaning that the host is acting as a router.
605 Returns 1 when ICMP redirects may be sent by the host.
606 This option is ignored unless the host is routing IP packets,
607 and should normally be enabled on all systems.
609 The maximum time-to-live (hop count) value for an IP packet sourced by
611 This value applies to normal transport protocols, not to ICMP.
613 Returns 1 when UDP checksums are being computed and checked.
614 Disabling UDP checksums is strongly discouraged.
616 For variables net.inet.*.ipsec, please refer to
620 Get or set various global information about the IPv6
621 (Internet Protocol version 6).
622 The third level name is the protocol.
623 The fourth level name is the variable name.
625 For variables net.inet6.* please refer to
627 For variables net.inet6.*.ipsec6, please refer to
631 The string and integer information available for the CTL_USER level
633 The changeable column shows whether a process with appropriate
634 privilege may change the value.
635 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
636 .It Sy "Second level name Type Changeable"
637 .It "USER_BC_BASE_MAX integer no"
638 .It "USER_BC_DIM_MAX integer no"
639 .It "USER_BC_SCALE_MAX integer no"
640 .It "USER_BC_STRING_MAX integer no"
641 .It "USER_COLL_WEIGHTS_MAX integer no"
642 .It "USER_CS_PATH string no"
643 .It "USER_EXPR_NEST_MAX integer no"
644 .It "USER_LINE_MAX integer no"
645 .It "USER_POSIX2_CHAR_TERM integer no"
646 .It "USER_POSIX2_C_BIND integer no"
647 .It "USER_POSIX2_C_DEV integer no"
648 .It "USER_POSIX2_FORT_DEV integer no"
649 .It "USER_POSIX2_FORT_RUN integer no"
650 .It "USER_POSIX2_LOCALEDEF integer no"
651 .It "USER_POSIX2_SW_DEV integer no"
652 .It "USER_POSIX2_UPE integer no"
653 .It "USER_POSIX2_VERSION integer no"
654 .It "USER_RE_DUP_MAX integer no"
655 .It "USER_STREAM_MAX integer no"
656 .It "USER_TZNAME_MAX integer no"
659 .It Li USER_BC_BASE_MAX
660 The maximum ibase/obase values in the
663 .It Li USER_BC_DIM_MAX
664 The maximum array size in the
667 .It Li USER_BC_SCALE_MAX
668 The maximum scale value in the
671 .It Li USER_BC_STRING_MAX
672 The maximum string length in the
675 .It Li USER_COLL_WEIGHTS_MAX
676 The maximum number of weights that can be assigned to any entry of
677 the LC_COLLATE order keyword in the locale definition file.
679 Return a value for the
681 environment variable that finds all the standard utilities.
682 .It Li USER_EXPR_NEST_MAX
683 The maximum number of expressions that can be nested within
688 The maximum length in bytes of a text-processing utility's input
690 .It Li USER_POSIX2_CHAR_TERM
691 Return 1 if the system supports at least one terminal type capable of
692 all operations described in
695 .It Li USER_POSIX2_C_BIND
696 Return 1 if the system's C-language development facilities support the
697 C-Language Bindings Option, otherwise 0.
698 .It Li USER_POSIX2_C_DEV
699 Return 1 if the system supports the C-Language Development Utilities Option,
701 .It Li USER_POSIX2_FORT_DEV
702 Return 1 if the system supports the FORTRAN Development Utilities Option,
704 .It Li USER_POSIX2_FORT_RUN
705 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
707 .It Li USER_POSIX2_LOCALEDEF
708 Return 1 if the system supports the creation of locales, otherwise 0.
709 .It Li USER_POSIX2_SW_DEV
710 Return 1 if the system supports the Software Development Utilities Option,
712 .It Li USER_POSIX2_UPE
713 Return 1 if the system supports the User Portability Utilities Option,
715 .It Li USER_POSIX2_VERSION
718 with which the system attempts to comply.
719 .It Li USER_RE_DUP_MAX
720 The maximum number of repeated occurrences of a regular expression
721 permitted when using interval notation.
722 .It Li USER_STREAM_MAX
723 The minimum maximum number of streams that a process may have open
725 .It Li USER_TZNAME_MAX
726 The minimum maximum number of types supported for the name of a
730 The string and integer information available for the CTL_VM level
732 The changeable column shows whether a process with appropriate
733 privilege may change the value.
734 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
735 .It Sy "Second level name Type Changeable"
736 .It "VM_LOADAVG struct loadavg no"
737 .It "VM_TOTAL struct vmtotal no"
738 .It "VM_SWAPPING_ENABLED integer maybe"
739 .It "VM_V_CACHE_MAX integer yes"
740 .It "VM_V_CACHE_MIN integer yes"
741 .It "VM_V_FREE_MIN integer yes"
742 .It "VM_V_FREE_RESERVED integer yes"
743 .It "VM_V_FREE_TARGET integer yes"
744 .It "VM_V_INACTIVE_TARGET integer yes"
745 .It "VM_V_PAGEOUT_FREE_MIN integer yes"
749 Return the load average history.
750 The returned data consists of a
753 Return the system wide virtual memory statistics.
754 The returned data consists of a
756 .It Li VM_SWAPPING_ENABLED
757 1 if process swapping is enabled or 0 if disabled.
759 permanently set to 0 if the kernel was built with swapping disabled.
760 .It Li VM_V_CACHE_MAX
761 Maximum desired size of the cache queue.
762 .It Li VM_V_CACHE_MIN
763 Minimum desired size of the cache queue.
764 If the cache queue size
765 falls very far below this value, the pageout daemon is awakened.
767 Minimum amount of memory (cache memory plus free memory)
768 required to be available before a process waiting on memory will be
770 .It Li VM_V_FREE_RESERVED
771 Processes will awaken the pageout daemon and wait for memory if the
772 number of free and cached pages drops below this value.
773 .It Li VM_V_FREE_TARGET
774 The total amount of free memory (including cache memory) that the
775 pageout daemon tries to maintain.
776 .It Li VM_V_INACTIVE_TARGET
777 The desired number of inactive pages that the pageout daemon should
778 achieve when it runs.
779 Inactive pages can be quickly inserted into
780 process address space when needed.
781 .It Li VM_V_PAGEOUT_FREE_MIN
782 If the amount of free and cache memory falls below this value, the
783 pageout daemon will enter "memory conserving mode" to avoid deadlock.
788 .Bl -tag -width <netinet/icmpXvar.h> -compact
790 definitions for top level identifiers, second level kernel and hardware
791 identifiers, and user level identifiers
793 definitions for second level network identifiers
795 definitions for third level profiling identifiers
797 definitions for second level virtual memory identifiers
799 definitions for third level IPv4/IPv6 identifiers and
800 fourth level IPv4/v6 identifiers
801 .It In netinet/icmp_var.h
802 definitions for fourth level ICMP identifiers
803 .It In netinet/icmp6.h
804 definitions for fourth level ICMPv6 identifiers
805 .It In netinet/udp_var.h
806 definitions for fourth level UDP identifiers
809 The following errors may be reported:
818 contains an invalid address.
822 array is less than two or greater than CTL_MAXNAME.
826 is given and its specified length in
828 is too large or too small.
830 The length pointed to by
832 is too short to hold the requested value.
834 The smaller of either the length pointed to by
836 or the estimated size of the returned data exceeds the
837 system limit on locked memory.
841 or a portion of the buffer if the estimated size of the data
842 to be returned is smaller,
843 would cause the process to exceed its per-process locked memory limit.
847 array specifies an intermediate rather than terminal name.
851 array specifies a terminal name, but the actual name is not terminal.
855 array specifies a value that is unknown.
857 An attempt is made to set a read-only value.
859 A process without appropriate privilege attempts to set a value.
869 function first appeared in