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28 .\" @(#)sysctl.3 8.4 (Berkeley) 5/9/95
38 .Nd get or set system information
45 .Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
47 .Fn sysctlbyname "const char *name" "void *oldp" "size_t *oldlenp" "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.
187 .Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
188 .It Sy "Name Next level names Description"
189 .It "CTL_DEBUG sys/sysctl.h Debugging"
190 .It "CTL_VFS sys/mount.h File system"
191 .It "CTL_HW sys/sysctl.h Generic CPU, I/O"
192 .It "CTL_KERN sys/sysctl.h High kernel limits"
193 .It "CTL_MACHDEP sys/sysctl.h Machine dependent"
194 .It "CTL_NET sys/socket.h Networking"
195 .It "CTL_USER sys/sysctl.h User-level"
196 .It "CTL_VM vm/vm_param.h Virtual memory"
199 For example, the following retrieves the maximum number of processes allowed
202 .Bd -literal -offset indent -compact
207 mib[1] = KERN_MAXPROC;
208 len = sizeof(maxproc);
209 sysctl(mib, 2, &maxproc, &len, NULL, 0);
212 To retrieve the standard search path for the system utilities:
214 .Bd -literal -offset indent -compact
220 mib[1] = USER_CS_PATH;
221 sysctl(mib, 2, NULL, &len, NULL, 0);
223 sysctl(mib, 2, p, &len, NULL, 0);
226 The debugging variables vary from system to system.
227 A debugging variable may be added or deleted without need to recompile
232 gets the list of debugging variables from the kernel and
233 displays their current values.
234 The system defines twenty
235 .Pq Vt "struct ctldebug"
240 They are declared as separate variables so that they can be
241 individually initialized at the location of their associated variable.
242 The loader prevents multiple use of the same variable by issuing errors
243 if a variable is initialized in more than one place.
244 For example, to export the variable
246 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 file systems.
255 One of its third level identifiers is VFS_MAXTYPENUM
256 that gives the highest valid file system type number.
257 Its other third level identifier is VFS_CONF that
258 returns configuration information about the file system
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 file system type number returned by a
265 call or from VFS_CONF.
266 The third level identifiers available for each file system
267 are given in the header file that defines the mount
268 argument structure for that file system.
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_DISKNAMES integer no"
284 .\".It "HW_DISKSTATS integer no"
285 .It "HW_FLOATINGPT integer no"
286 .It "HW_MACHINE_ARCH string no"
287 .It "HW_REALMEM 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 Fa HW_DISKNAMES
305 .\".It Fa HW_DISKSTATS
307 Nonzero if the floating point support is in hardware.
308 .It Li HW_MACHINE_ARCH
309 The machine dependent architecture type.
311 The bytes of real memory.
314 The string and integer information available for the CTL_KERN level
316 The changeable column shows whether a process with appropriate
317 privilege may change the value.
318 The types of data currently available are process information,
319 system vnodes, the open file entries, routing table entries,
320 virtual memory statistics, load average history, and clock rate
322 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
323 .It Sy "Second level name Type Changeable"
324 .It "KERN_ARGMAX integer no"
325 .It "KERN_BOOTFILE string yes"
326 .It "KERN_BOOTTIME struct timeval no"
327 .It "KERN_CLOCKRATE struct clockinfo no"
328 .It "KERN_FILE struct xfile no"
329 .It "KERN_HOSTID integer yes"
330 .It "KERN_HOSTUUID string yes"
331 .It "KERN_HOSTNAME string yes"
332 .It "KERN_JOB_CONTROL integer no"
333 .It "KERN_MAXFILES integer yes"
334 .It "KERN_MAXFILESPERPROC integer yes"
335 .It "KERN_MAXPROC integer no"
336 .It "KERN_MAXPROCPERUID integer yes"
337 .It "KERN_MAXVNODES integer yes"
338 .It "KERN_NGROUPS integer no"
339 .It "KERN_NISDOMAINNAME string yes"
340 .It "KERN_OSRELDATE integer no"
341 .It "KERN_OSRELEASE string no"
342 .It "KERN_OSREV integer no"
343 .It "KERN_OSTYPE string no"
344 .It "KERN_POSIX1 integer no"
345 .It "KERN_PROC node not applicable"
346 .It "KERN_PROF node not applicable"
347 .It "KERN_QUANTUM integer yes"
348 .It "KERN_SAVED_IDS integer no"
349 .It "KERN_SECURELVL integer raise only"
350 .It "KERN_UPDATEINTERVAL integer no"
351 .It "KERN_VERSION string no"
352 .It "KERN_VNODE struct xvnode 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 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 host's universally unique identifier (UUID).
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 kernel release version in the format
409 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
412 is the major version,
414 is the two digit minor version,
416 is 0 if release branch, otherwise 1,
419 is updated when the available APIs change.
421 The userland release version is available from
423 parse this file if you need to get the release version of
424 the currently installed userland.
425 .It Li KERN_OSRELEASE
426 The system release string.
428 The system revision string.
430 The system type string.
434 with which the system
437 Return selected information about specific running processes.
439 For the following names, an array of
440 .Va struct kinfo_proc
441 structures is returned,
442 whose size depends on the current number of such objects in the system.
443 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
444 .It "Third level name Fourth level is:"
445 .It "KERN_PROC_ALL None"
446 .It "KERN_PROC_PID A process ID"
447 .It "KERN_PROC_PGRP A process group"
448 .It "KERN_PROC_TTY A tty device"
449 .It "KERN_PROC_UID A user ID"
450 .It "KERN_PROC_RUID A real user ID"
453 If the third level name is
455 then the command line argument
456 array is returned in a flattened form, i.e., zero-terminated arguments
458 The total size of array is returned.
459 It is also possible for a process to set its own process title this way.
460 If the third level name is
461 .Dv KERN_PROC_PATHNAME ,
463 process' text file is stored.
465 .Dv KERN_PROC_PATHNAME ,
468 implies the current process.
469 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
470 .It Sy "Third level name Fourth level is:"
471 .It Dv KERN_PROC_ARGS Ta "A process ID"
472 .It Dv KERN_PROC_PATHNAME Ta "A process ID"
475 Return profiling information about the kernel.
476 If the kernel is not compiled for profiling,
477 attempts to retrieve any of the KERN_PROF values will
480 The third level names for the string and integer profiling information
482 The changeable column shows whether a process with appropriate
483 privilege may change the value.
484 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
485 .It Sy "Third level name Type Changeable"
486 .It "GPROF_STATE integer yes"
487 .It "GPROF_COUNT u_short[\|] yes"
488 .It "GPROF_FROMS u_short[\|] yes"
489 .It "GPROF_TOS struct tostruct yes"
490 .It "GPROF_GMONPARAM struct gmonparam no"
493 The variables are as follows:
496 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
497 is running or stopped.
499 Array of statistical program counter counts.
501 Array indexed by program counter of call-from points.
505 describing destination of calls and their counts.
506 .It Li GPROF_GMONPARAM
507 Structure giving the sizes of the above arrays.
510 The maximum period of time, in microseconds, for which a process is allowed
511 to run without being preempted if other processes are in the run queue.
512 .It Li KERN_SAVED_IDS
513 Returns 1 if saved set-group and saved set-user ID is available.
514 .It Li KERN_SECURELVL
515 The system security level.
516 This level may be raised by processes with appropriate privilege.
517 It may not be lowered.
519 The system version string.
521 Return the entire vnode table.
522 Note, the vnode table is not necessarily a consistent snapshot of
524 The returned data consists of an array whose size depends on the
525 current number of such objects in the system.
526 Each element of the array consists of a
530 The string and integer information available for the CTL_NET level
532 The changeable column shows whether a process with appropriate
533 privilege may change the value.
534 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
535 .It Sy "Second level name Type Changeable"
536 .It "PF_ROUTE routing messages no"
537 .It "PF_INET IPv4 values yes"
538 .It "PF_INET6 IPv6 values yes"
542 Return the entire routing table or a subset of it.
543 The data is returned as a sequence of routing messages (see
545 for the header file, format and meaning).
546 The length of each message is contained in the message header.
548 The third level name is a protocol number, which is currently always 0.
549 The fourth level name is an address family, which may be set to 0 to
550 select all address families.
551 The fifth and sixth level names are as follows:
552 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
553 .It Sy "Fifth level name Sixth level is:"
554 .It "NET_RT_FLAGS rtflags"
555 .It "NET_RT_DUMP None"
556 .It "NET_RT_IFLIST 0 or if_index"
557 .It "NET_RT_IFMALIST 0 or if_index"
562 name returns information about multicast group memberships on all interfaces
563 if 0 is specified, or for the interface specified by
566 Get or set various global information about the IPv4
567 (Internet Protocol version 4).
568 The third level name is the protocol.
569 The fourth level name is the variable name.
570 The currently defined protocols and names are:
571 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
572 .It Sy "Protocol Variable Type Changeable"
573 .It "icmp bmcastecho integer yes"
574 .It "icmp maskrepl integer yes"
575 .It "ip forwarding integer yes"
576 .It "ip redirect integer yes"
577 .It "ip ttl integer yes"
578 .It "udp checksum integer yes"
581 The variables are as follows:
583 .It Li icmp.bmcastecho
584 Returns 1 if an ICMP echo request to a broadcast or multicast address is
587 Returns 1 if ICMP network mask requests are to be answered.
589 Returns 1 when IP forwarding is enabled for the host,
590 meaning that the host is acting as a router.
592 Returns 1 when ICMP redirects may be sent by the host.
593 This option is ignored unless the host is routing IP packets,
594 and should normally be enabled on all systems.
596 The maximum time-to-live (hop count) value for an IP packet sourced by
598 This value applies to normal transport protocols, not to ICMP.
600 Returns 1 when UDP checksums are being computed and checked.
601 Disabling UDP checksums is strongly discouraged.
603 For variables net.inet.*.ipsec, please refer to
607 Get or set various global information about the IPv6
608 (Internet Protocol version 6).
609 The third level name is the protocol.
610 The fourth level name is the variable name.
612 For variables net.inet6.* please refer to
614 For variables net.inet6.*.ipsec6, please refer to
618 The string and integer information available for the CTL_USER level
620 The changeable column shows whether a process with appropriate
621 privilege may change the value.
622 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
623 .It Sy "Second level name Type Changeable"
624 .It "USER_BC_BASE_MAX integer no"
625 .It "USER_BC_DIM_MAX integer no"
626 .It "USER_BC_SCALE_MAX integer no"
627 .It "USER_BC_STRING_MAX integer no"
628 .It "USER_COLL_WEIGHTS_MAX integer no"
629 .It "USER_CS_PATH string no"
630 .It "USER_EXPR_NEST_MAX integer no"
631 .It "USER_LINE_MAX integer no"
632 .It "USER_POSIX2_CHAR_TERM integer no"
633 .It "USER_POSIX2_C_BIND integer no"
634 .It "USER_POSIX2_C_DEV integer no"
635 .It "USER_POSIX2_FORT_DEV integer no"
636 .It "USER_POSIX2_FORT_RUN integer no"
637 .It "USER_POSIX2_LOCALEDEF integer no"
638 .It "USER_POSIX2_SW_DEV integer no"
639 .It "USER_POSIX2_UPE integer no"
640 .It "USER_POSIX2_VERSION integer no"
641 .It "USER_RE_DUP_MAX integer no"
642 .It "USER_STREAM_MAX integer no"
643 .It "USER_TZNAME_MAX integer no"
646 .It Li USER_BC_BASE_MAX
647 The maximum ibase/obase values in the
650 .It Li USER_BC_DIM_MAX
651 The maximum array size in the
654 .It Li USER_BC_SCALE_MAX
655 The maximum scale value in the
658 .It Li USER_BC_STRING_MAX
659 The maximum string length in the
662 .It Li USER_COLL_WEIGHTS_MAX
663 The maximum number of weights that can be assigned to any entry of
664 the LC_COLLATE order keyword in the locale definition file.
666 Return a value for the
668 environment variable that finds all the standard utilities.
669 .It Li USER_EXPR_NEST_MAX
670 The maximum number of expressions that can be nested within
675 The maximum length in bytes of a text-processing utility's input
677 .It Li USER_POSIX2_CHAR_TERM
678 Return 1 if the system supports at least one terminal type capable of
679 all operations described in
682 .It Li USER_POSIX2_C_BIND
683 Return 1 if the system's C-language development facilities support the
684 C-Language Bindings Option, otherwise 0.
685 .It Li USER_POSIX2_C_DEV
686 Return 1 if the system supports the C-Language Development Utilities Option,
688 .It Li USER_POSIX2_FORT_DEV
689 Return 1 if the system supports the FORTRAN Development Utilities Option,
691 .It Li USER_POSIX2_FORT_RUN
692 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
694 .It Li USER_POSIX2_LOCALEDEF
695 Return 1 if the system supports the creation of locales, otherwise 0.
696 .It Li USER_POSIX2_SW_DEV
697 Return 1 if the system supports the Software Development Utilities Option,
699 .It Li USER_POSIX2_UPE
700 Return 1 if the system supports the User Portability Utilities Option,
702 .It Li USER_POSIX2_VERSION
705 with which the system attempts to comply.
706 .It Li USER_RE_DUP_MAX
707 The maximum number of repeated occurrences of a regular expression
708 permitted when using interval notation.
709 .It Li USER_STREAM_MAX
710 The minimum maximum number of streams that a process may have open
712 .It Li USER_TZNAME_MAX
713 The minimum maximum number of types supported for the name of a
717 The string and integer information available for the CTL_VM level
719 The changeable column shows whether a process with appropriate
720 privilege may change the value.
721 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
722 .It Sy "Second level name Type Changeable"
723 .It "VM_LOADAVG struct loadavg no"
724 .It "VM_TOTAL struct vmtotal no"
725 .It "VM_PAGEOUT_ALGORITHM integer yes"
726 .It "VM_SWAPPING_ENABLED integer maybe"
727 .It "VM_V_CACHE_MAX integer yes"
728 .It "VM_V_CACHE_MIN integer yes"
729 .It "VM_V_FREE_MIN integer yes"
730 .It "VM_V_FREE_RESERVED integer yes"
731 .It "VM_V_FREE_TARGET integer yes"
732 .It "VM_V_INACTIVE_TARGET integer yes"
733 .It "VM_V_PAGEOUT_FREE_MIN integer yes"
737 Return the load average history.
738 The returned data consists of a
741 Return the system wide virtual memory statistics.
742 The returned data consists of a
744 .It Li VM_PAGEOUT_ALGORITHM
745 0 if the statistics-based page management algorithm is in use
746 or 1 if the near-LRU algorithm is in use.
747 .It Li VM_SWAPPING_ENABLED
748 1 if process swapping is enabled or 0 if disabled.
750 permanently set to 0 if the kernel was built with swapping disabled.
751 .It Li VM_V_CACHE_MAX
752 Maximum desired size of the cache queue.
753 .It Li VM_V_CACHE_MIN
754 Minimum desired size of the cache queue.
755 If the cache queue size
756 falls very far below this value, the pageout daemon is awakened.
758 Minimum amount of memory (cache memory plus free memory)
759 required to be available before a process waiting on memory will be
761 .It Li VM_V_FREE_RESERVED
762 Processes will awaken the pageout daemon and wait for memory if the
763 number of free and cached pages drops below this value.
764 .It Li VM_V_FREE_TARGET
765 The total amount of free memory (including cache memory) that the
766 pageout daemon tries to maintain.
767 .It Li VM_V_INACTIVE_TARGET
768 The desired number of inactive pages that the pageout daemon should
769 achieve when it runs.
770 Inactive pages can be quickly inserted into
771 process address space when needed.
772 .It Li VM_V_PAGEOUT_FREE_MIN
773 If the amount of free and cache memory falls below this value, the
774 pageout daemon will enter "memory conserving mode" to avoid deadlock.
779 .Bl -tag -width <netinet/icmpXvar.h> -compact
781 definitions for top level identifiers, second level kernel and hardware
782 identifiers, and user level identifiers
784 definitions for second level network identifiers
786 definitions for third level profiling identifiers
788 definitions for second level virtual memory identifiers
790 definitions for third level IPv4/IPv6 identifiers and
791 fourth level IPv4/v6 identifiers
792 .It In netinet/icmp_var.h
793 definitions for fourth level ICMP identifiers
794 .It In netinet/icmp6.h
795 definitions for fourth level ICMPv6 identifiers
796 .It In netinet/udp_var.h
797 definitions for fourth level UDP identifiers
800 The following errors may be reported:
809 contains an invalid address.
813 array is less than two or greater than CTL_MAXNAME.
817 is given and its specified length in
819 is too large or too small.
821 The length pointed to by
823 is too short to hold the requested value.
825 The smaller of either the length pointed to by
827 or the estimated size of the returned data exceeds the
828 system limit on locked memory.
832 or a portion of the buffer if the estimated size of the data
833 to be returned is smaller,
834 would cause the process to exceed its per-process locked memory limit.
838 array specifies an intermediate rather than terminal name.
842 array specifies a terminal name, but the actual name is not terminal.
846 array specifies a value that is unknown.
848 An attempt is made to set a read-only value.
850 A process without appropriate privilege attempts to set a value.
860 function first appeared in