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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"
298 The byteorder (4,321, or 1,234).
300 The bytes of physical memory.
302 The bytes of non-kernel memory.
304 The software page size.
305 .\".It Fa HW_DISKNAMES
306 .\".It Fa HW_DISKSTATS
308 Nonzero if the floating point support is in hardware.
309 .It Li HW_MACHINE_ARCH
310 The machine dependent architecture type.
312 The bytes of real memory.
315 The string and integer information available for the CTL_KERN level
317 The changeable column shows whether a process with appropriate
318 privilege may change the value.
319 The types of data currently available are process information,
320 system vnodes, the open file entries, routing table entries,
321 virtual memory statistics, load average history, and clock rate
323 .Bl -column "KERNXMAXFILESPERPROCXXX" "struct clockrateXXX" -offset indent
324 .It Sy "Second level name Type Changeable"
325 .It "KERN_ARGMAX integer no"
326 .It "KERN_BOOTFILE string yes"
327 .It "KERN_BOOTTIME struct timeval no"
328 .It "KERN_CLOCKRATE struct clockinfo no"
329 .It "KERN_FILE struct xfile no"
330 .It "KERN_HOSTID integer yes"
331 .It "KERN_HOSTUUID string yes"
332 .It "KERN_HOSTNAME string yes"
333 .It "KERN_JOB_CONTROL integer no"
334 .It "KERN_MAXFILES integer yes"
335 .It "KERN_MAXFILESPERPROC integer yes"
336 .It "KERN_MAXPROC integer no"
337 .It "KERN_MAXPROCPERUID integer yes"
338 .It "KERN_MAXVNODES integer yes"
339 .It "KERN_NGROUPS integer no"
340 .It "KERN_NISDOMAINNAME string yes"
341 .It "KERN_OSRELDATE integer no"
342 .It "KERN_OSRELEASE string no"
343 .It "KERN_OSREV integer no"
344 .It "KERN_OSTYPE string no"
345 .It "KERN_POSIX1 integer no"
346 .It "KERN_PROC node not applicable"
347 .It "KERN_PROF node not applicable"
348 .It "KERN_QUANTUM integer yes"
349 .It "KERN_SAVED_IDS integer no"
350 .It "KERN_SECURELVL integer raise only"
351 .It "KERN_UPDATEINTERVAL integer no"
352 .It "KERN_VERSION string no"
353 .It "KERN_VNODE struct xvnode no"
358 The maximum bytes of argument to
361 The full pathname of the file from which the kernel was loaded.
365 structure is returned.
366 This structure contains the time that the system was booted.
367 .It Li KERN_CLOCKRATE
370 structure is returned.
371 This structure contains the clock, statistics clock and profiling clock
372 frequencies, the number of micro-seconds per hz tick and the skew rate.
374 Return the entire file table.
375 The returned data consists of an array of
377 whose size depends on the current number of such objects in the system.
379 Get or set the host ID.
381 Get or set the host's universally unique identifier (UUID).
383 Get or set the hostname.
384 .It Li KERN_JOB_CONTROL
385 Return 1 if job control is available on this system, otherwise 0.
387 The maximum number of files that may be open in the system.
388 .It Li KERN_MAXFILESPERPROC
389 The maximum number of files that may be open for a single process.
390 This limit only applies to processes with an effective uid of nonzero
391 at the time of the open request.
392 Files that have already been opened are not affected if the limit
393 or the effective uid is changed.
395 The maximum number of concurrent processes the system will allow.
396 .It Li KERN_MAXPROCPERUID
397 The maximum number of concurrent processes the system will allow
398 for a single effective uid.
399 This limit only applies to processes with an effective uid of nonzero
400 at the time of a fork request.
401 Processes that have already been started are not affected if the limit
403 .It Li KERN_MAXVNODES
404 The maximum number of vnodes available on the system.
406 The maximum number of supplemental groups.
407 .It Li KERN_NISDOMAINNAME
408 The name of the current YP/NIS domain.
409 .It Li KERN_OSRELDATE
410 The kernel release version in the format
411 .Ar M Ns Ar mm Ns Ar R Ns Ar xx ,
414 is the major version,
416 is the two digit minor version,
418 is 0 if release branch, otherwise 1,
421 is updated when the available APIs change.
423 The userland release version is available from
425 parse this file if you need to get the release version of
426 the currently installed userland.
427 .It Li KERN_OSRELEASE
428 The system release string.
430 The system revision string.
432 The system type string.
436 with which the system
439 Return selected information about specific running processes.
441 For the following names, an array of
442 .Va struct kinfo_proc
443 structures is returned,
444 whose size depends on the current number of such objects in the system.
445 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
446 .It "Third level name Fourth level is:"
447 .It "KERN_PROC_ALL None"
448 .It "KERN_PROC_PID A process ID"
449 .It "KERN_PROC_PGRP A process group"
450 .It "KERN_PROC_TTY A tty device"
451 .It "KERN_PROC_UID A user ID"
452 .It "KERN_PROC_RUID A real user ID"
455 If the third level name is
457 then the command line argument
458 array is returned in a flattened form, i.e., zero-terminated arguments
460 The total size of array is returned.
461 It is also possible for a process to set its own process title this way.
462 If the third level name is
463 .Dv KERN_PROC_PATHNAME ,
465 process' text file is stored.
467 .Dv KERN_PROC_PATHNAME ,
470 implies the current process.
471 .Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
472 .It Sy "Third level name Fourth level is:"
473 .It Dv KERN_PROC_ARGS Ta "A process ID"
474 .It Dv KERN_PROC_PATHNAME Ta "A process ID"
477 Return profiling information about the kernel.
478 If the kernel is not compiled for profiling,
479 attempts to retrieve any of the KERN_PROF values will
482 The third level names for the string and integer profiling information
484 The changeable column shows whether a process with appropriate
485 privilege may change the value.
486 .Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
487 .It Sy "Third level name Type Changeable"
488 .It "GPROF_STATE integer yes"
489 .It "GPROF_COUNT u_short[\|] yes"
490 .It "GPROF_FROMS u_short[\|] yes"
491 .It "GPROF_TOS struct tostruct yes"
492 .It "GPROF_GMONPARAM struct gmonparam no"
495 The variables are as follows:
498 Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
499 is running or stopped.
501 Array of statistical program counter counts.
503 Array indexed by program counter of call-from points.
507 describing destination of calls and their counts.
508 .It Li GPROF_GMONPARAM
509 Structure giving the sizes of the above arrays.
512 The maximum period of time, in microseconds, for which a process is allowed
513 to run without being preempted if other processes are in the run queue.
514 .It Li KERN_SAVED_IDS
515 Returns 1 if saved set-group and saved set-user ID is available.
516 .It Li KERN_SECURELVL
517 The system security level.
518 This level may be raised by processes with appropriate privilege.
519 It may not be lowered.
521 The system version string.
523 Return the entire vnode table.
524 Note, the vnode table is not necessarily a consistent snapshot of
526 The returned data consists of an array whose size depends on the
527 current number of such objects in the system.
528 Each element of the array consists of a
532 The string and integer information available for the CTL_NET level
534 The changeable column shows whether a process with appropriate
535 privilege may change the value.
536 .Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
537 .It Sy "Second level name Type Changeable"
538 .It "PF_ROUTE routing messages no"
539 .It "PF_INET IPv4 values yes"
540 .It "PF_INET6 IPv6 values yes"
545 Return the entire routing table or a subset of it.
546 The data is returned as a sequence of routing messages (see
548 for the header file, format and meaning).
549 The length of each message is contained in the message header.
551 The third level name is a protocol number, which is currently always 0.
552 The fourth level name is an address family, which may be set to 0 to
553 select all address families.
554 The fifth and sixth level names are as follows:
555 .Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
556 .It Sy "Fifth level name Sixth level is:"
557 .It "NET_RT_FLAGS rtflags"
558 .It "NET_RT_DUMP None"
559 .It "NET_RT_IFLIST 0 or if_index"
560 .It "NET_RT_IFMALIST 0 or if_index"
565 name returns information about multicast group memberships on all interfaces
566 if 0 is specified, or for the interface specified by
569 Get or set various global information about the IPv4
570 (Internet Protocol version 4).
571 The third level name is the protocol.
572 The fourth level name is the variable name.
573 The currently defined protocols and names are:
574 .Bl -column ProtocolXX VariableXX TypeXX ChangeableXX
575 .It Sy "Protocol Variable Type Changeable"
576 .It "icmp bmcastecho integer yes"
577 .It "icmp maskrepl integer yes"
578 .It "ip forwarding integer yes"
579 .It "ip redirect integer yes"
580 .It "ip ttl integer yes"
581 .It "udp checksum integer yes"
584 The variables are as follows:
586 .It Li icmp.bmcastecho
587 Returns 1 if an ICMP echo request to a broadcast or multicast address is
590 Returns 1 if ICMP network mask requests are to be answered.
592 Returns 1 when IP forwarding is enabled for the host,
593 meaning that the host is acting as a router.
595 Returns 1 when ICMP redirects may be sent by the host.
596 This option is ignored unless the host is routing IP packets,
597 and should normally be enabled on all systems.
599 The maximum time-to-live (hop count) value for an IP packet sourced by
601 This value applies to normal transport protocols, not to ICMP.
603 Returns 1 when UDP checksums are being computed and checked.
604 Disabling UDP checksums is strongly discouraged.
606 For variables net.inet.*.ipsec, please refer to
610 Get or set various global information about the IPv6
611 (Internet Protocol version 6).
612 The third level name is the protocol.
613 The fourth level name is the variable name.
615 For variables net.inet6.* please refer to
617 For variables net.inet6.*.ipsec6, please refer to
621 The string and integer information available for the CTL_USER level
623 The changeable column shows whether a process with appropriate
624 privilege may change the value.
625 .Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
626 .It Sy "Second level name Type Changeable"
627 .It "USER_BC_BASE_MAX integer no"
628 .It "USER_BC_DIM_MAX integer no"
629 .It "USER_BC_SCALE_MAX integer no"
630 .It "USER_BC_STRING_MAX integer no"
631 .It "USER_COLL_WEIGHTS_MAX integer no"
632 .It "USER_CS_PATH string no"
633 .It "USER_EXPR_NEST_MAX integer no"
634 .It "USER_LINE_MAX integer no"
635 .It "USER_POSIX2_CHAR_TERM integer no"
636 .It "USER_POSIX2_C_BIND integer no"
637 .It "USER_POSIX2_C_DEV integer no"
638 .It "USER_POSIX2_FORT_DEV integer no"
639 .It "USER_POSIX2_FORT_RUN integer no"
640 .It "USER_POSIX2_LOCALEDEF integer no"
641 .It "USER_POSIX2_SW_DEV integer no"
642 .It "USER_POSIX2_UPE integer no"
643 .It "USER_POSIX2_VERSION integer no"
644 .It "USER_RE_DUP_MAX integer no"
645 .It "USER_STREAM_MAX integer no"
646 .It "USER_TZNAME_MAX integer no"
650 .It Li USER_BC_BASE_MAX
651 The maximum ibase/obase values in the
654 .It Li USER_BC_DIM_MAX
655 The maximum array size in the
658 .It Li USER_BC_SCALE_MAX
659 The maximum scale value in the
662 .It Li USER_BC_STRING_MAX
663 The maximum string length in the
666 .It Li USER_COLL_WEIGHTS_MAX
667 The maximum number of weights that can be assigned to any entry of
668 the LC_COLLATE order keyword in the locale definition file.
670 Return a value for the
672 environment variable that finds all the standard utilities.
673 .It Li USER_EXPR_NEST_MAX
674 The maximum number of expressions that can be nested within
679 The maximum length in bytes of a text-processing utility's input
681 .It Li USER_POSIX2_CHAR_TERM
682 Return 1 if the system supports at least one terminal type capable of
683 all operations described in
686 .It Li USER_POSIX2_C_BIND
687 Return 1 if the system's C-language development facilities support the
688 C-Language Bindings Option, otherwise 0.
689 .It Li USER_POSIX2_C_DEV
690 Return 1 if the system supports the C-Language Development Utilities Option,
692 .It Li USER_POSIX2_FORT_DEV
693 Return 1 if the system supports the FORTRAN Development Utilities Option,
695 .It Li USER_POSIX2_FORT_RUN
696 Return 1 if the system supports the FORTRAN Runtime Utilities Option,
698 .It Li USER_POSIX2_LOCALEDEF
699 Return 1 if the system supports the creation of locales, otherwise 0.
700 .It Li USER_POSIX2_SW_DEV
701 Return 1 if the system supports the Software Development Utilities Option,
703 .It Li USER_POSIX2_UPE
704 Return 1 if the system supports the User Portability Utilities Option,
706 .It Li USER_POSIX2_VERSION
709 with which the system attempts to comply.
710 .It Li USER_RE_DUP_MAX
711 The maximum number of repeated occurrences of a regular expression
712 permitted when using interval notation.
713 .It Li USER_STREAM_MAX
714 The minimum maximum number of streams that a process may have open
716 .It Li USER_TZNAME_MAX
717 The minimum maximum number of types supported for the name of a
721 The string and integer information available for the CTL_VM level
723 The changeable column shows whether a process with appropriate
724 privilege may change the value.
725 .Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
726 .It Sy "Second level name Type Changeable"
727 .It "VM_LOADAVG struct loadavg no"
728 .It "VM_TOTAL struct vmtotal no"
729 .It "VM_PAGEOUT_ALGORITHM integer yes"
730 .It "VM_SWAPPING_ENABLED integer maybe"
731 .It "VM_V_CACHE_MAX integer yes"
732 .It "VM_V_CACHE_MIN integer yes"
733 .It "VM_V_FREE_MIN integer yes"
734 .It "VM_V_FREE_RESERVED integer yes"
735 .It "VM_V_FREE_TARGET integer yes"
736 .It "VM_V_INACTIVE_TARGET integer yes"
737 .It "VM_V_PAGEOUT_FREE_MIN integer yes"
742 Return the load average history.
743 The returned data consists of a
746 Return the system wide virtual memory statistics.
747 The returned data consists of a
749 .It Li VM_PAGEOUT_ALGORITHM
750 0 if the statistics-based page management algorithm is in use
751 or 1 if the near-LRU algorithm is in use.
752 .It Li VM_SWAPPING_ENABLED
753 1 if process swapping is enabled or 0 if disabled.
755 permanently set to 0 if the kernel was built with swapping disabled.
756 .It Li VM_V_CACHE_MAX
757 Maximum desired size of the cache queue.
758 .It Li VM_V_CACHE_MIN
759 Minimum desired size of the cache queue.
760 If the cache queue size
761 falls very far below this value, the pageout daemon is awakened.
763 Minimum amount of memory (cache memory plus free memory)
764 required to be available before a process waiting on memory will be
766 .It Li VM_V_FREE_RESERVED
767 Processes will awaken the pageout daemon and wait for memory if the
768 number of free and cached pages drops below this value.
769 .It Li VM_V_FREE_TARGET
770 The total amount of free memory (including cache memory) that the
771 pageout daemon tries to maintain.
772 .It Li VM_V_INACTIVE_TARGET
773 The desired number of inactive pages that the pageout daemon should
774 achieve when it runs.
775 Inactive pages can be quickly inserted into
776 process address space when needed.
777 .It Li VM_V_PAGEOUT_FREE_MIN
778 If the amount of free and cache memory falls below this value, the
779 pageout daemon will enter "memory conserving mode" to avoid deadlock.
784 .Bl -tag -width <netinet/icmpXvar.h> -compact
786 definitions for top level identifiers, second level kernel and hardware
787 identifiers, and user level identifiers
789 definitions for second level network identifiers
791 definitions for third level profiling identifiers
793 definitions for second level virtual memory identifiers
795 definitions for third level IPv4/IPv6 identifiers and
796 fourth level IPv4/v6 identifiers
797 .It In netinet/icmp_var.h
798 definitions for fourth level ICMP identifiers
799 .It In netinet/icmp6.h
800 definitions for fourth level ICMPv6 identifiers
801 .It In netinet/udp_var.h
802 definitions for fourth level UDP identifiers
805 The following errors may be reported:
814 contains an invalid address.
818 array is less than two or greater than CTL_MAXNAME.
822 is given and its specified length in
824 is too large or too small.
826 The length pointed to by
828 is too short to hold the requested value.
830 The smaller of either the length pointed to by
832 or the estimated size of the returned data exceeds the
833 system limit on locked memory.
837 or a portion of the buffer if the estimated size of the data
838 to be returned is smaller,
839 would cause the process to exceed its per-process locked memory limit.
843 array specifies an intermediate rather than terminal name.
847 array specifies a terminal name, but the actual name is not terminal.
851 array specifies a value that is unknown.
853 An attempt is made to set a read-only value.
855 A process without appropriate privilege attempts to set a value.
865 function first appeared in