xref: /freebsd/lib/libc/gen/sysctl.3 (revision ef5d438ed4bc17ad7ece3e40fe4d1f9baf3aadf7)
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32.\"	@(#)sysctl.3	8.1 (Berkeley) 6/4/93
33.\"
34.Dd "June 4, 1993"
35.Dt SYSCTL 3
36.Os
37.Sh NAME
38.Nm sysctl
39.Nd get or set system information
40.Sh SYNOPSIS
41.Fd #include <sys/sysctl.h>
42.Ft int
43.Fn sysctl "int *name" "u_int namelen" "void *oldp" "size_t *oldlenp" "void *newp" "size_t newlen"
44.Sh DESCRIPTION
45The
46.Nm sysctl
47function retrieves system information and allows processes with
48appropriate privileges to set system information.
49The information available from
50.Nm sysctl
51consists of integers, strings, and tables.
52Information may be retrieved and set from the command interface
53using the
54.Xr sysctl 8
55utility.
56.Pp
57Unless explicitly noted below,
58.Nm sysctl
59returns a consistent snapshot of the data requested.
60Consistency is obtained by locking the destination
61buffer into memory so that the data may be copied out without blocking.
62Calls to
63.Nm sysctl
64are serialized to avoid deadlock.
65.Pp
66The state is described using a ``Management Information Base'' (MIB)
67style name, listed in
68.Fa name ,
69which is a
70.Fa namelen
71length array of integers.
72.Pp
73The information is copied into the buffer specified by
74.Fa oldp .
75The size of the buffer is given by the location specified by
76.Fa oldlenp
77before the call,
78and that location gives the amount of data copied after a successful call.
79If the amount of data available is greater
80than the size of the buffer supplied,
81the call supplies as much data as fits in the buffer provided
82and returns with the error code ENOMEM.
83If the old value is not desired,
84.Fa oldp
85and
86.Fa oldlenp
87should be set to NULL.
88.Pp
89The size of the available data can be determined by calling
90.Nm sysctl
91with a NULL parameter for
92.Fa oldp .
93The size of the available data will be returned in the location pointed to by
94.Fa oldlenp .
95For some operations, the amount of space may change often.
96For these operations,
97the system attempts to round up so that the returned size is
98large enough for a call to return the data shortly thereafter.
99.Pp
100To set a new value,
101.Fa newp
102is set to point to a buffer of length
103.Fa newlen
104from which the requested value is to be taken.
105If a new value is not to be set,
106.Fa newp
107should be set to NULL and
108.Fa newlen
109set to 0.
110.Pp
111The top level names are defined with a CTL_ prefix in
112.Pa <sys/sysctl.h> ,
113and are as follows.
114The next and subsequent levels down are found in the include files
115listed here, and described in separate sections below.
116.Pp
117.Bl -column CTLXMACHDEPXXX "Next level namesXXXXXX" -offset indent
118.It Sy Pa Name	Next level names	Description
119.It CTL\_DEBUG	sys/sysctl.h	Debugging
120.It CTL\_FS	sys/sysctl.h	File system
121.It CTL\_HW	sys/sysctl.h	Generic CPU, I/O
122.It CTL\_KERN	sys/sysctl.h	High kernel limits
123.It CTL\_MACHDEP	sys/sysctl.h	Machine dependent
124.It CTL\_NET	sys/socket.h	Networking
125.It CTL\_USER	sys/sysctl.h	User-level
126.It CTL\_VM	vm/vm_param.h	Virtual memory
127.El
128.Pp
129For example, the following retrieves the maximum number of processes allowed
130in the system:
131.Bd -literal -offset indent -compact
132int mib[2], maxproc;
133size_t len;
134.sp
135mib[0] = CTL_KERN;
136mib[1] = KERN_MAXPROC;
137len = sizeof(maxproc);
138sysctl(mib, 2, &maxproc, &len, NULL, 0);
139.Ed
140.sp
141To retrieve the standard search path for the system utilities:
142.Bd -literal -offset indent -compact
143int mib[2];
144size_t len;
145char *p;
146.sp
147mib[0] = CTL_USER;
148mib[1] = USER_CS_PATH;
149sysctl(mib, 2, NULL, &len, NULL, 0);
150p = malloc(len);
151sysctl(mib, 2, p, &len, NULL, 0);
152.Ed
153.Sh CTL_DEBUG
154The debugging variables vary from system to system.
155A debugging variable may be added or deleted without need to recompile
156.Nm sysctl
157to know about it.
158Each time it runs,
159.Nm sysctl
160gets the list of debugging variables from the kernel and
161displays their current values.
162The system defines twenty
163.Ns ( Va struct ctldebug )
164variables named
165.Nm debug0
166through
167.Nm debug19 .
168They are declared as separate variables so that they can be
169individually initialized at the location of their associated variable.
170The loader prevents multiple use of the same variable by issuing errors
171if a variable is initialized in more than one place.
172For example, to export the variable
173.Nm dospecialcheck
174as a debugging variable, the following declaration would be used:
175.Bd -literal -offset indent -compact
176int dospecialcheck = 1;
177struct ctldebug debug5 = { "dospecialcheck", &dospecialcheck };
178.Ed
179.Sh CTL_FS
180There are currently no second level names for the file system.
181.Sh CTL_HW
182The string and integer information available for the CTL_HW level
183is detailed below.
184The changeable column shows whether a process with appropriate
185privilege may change the value.
186.Bl -column "Second level nameXXXXXX" integerXXX -offset indent
187.It Sy Pa Second level name	Type	Changeable
188.It HW\_MACHINE	string	no
189.It HW\_MODEL	string	no
190.It HW\_NCPU	integer	no
191.It HW\_BYTEORDER	integer	no
192.It HW\_PHYSMEM	integer	no
193.It HW\_USERMEM	integer	no
194.It HW\_PAGESIZE	integer	no
195.\".It HW\_DISKNAMES	integer	no
196.\".It HW\_DISKSTATS	integer	no
197.El
198.Pp
199.Bl -tag -width "123456"
200.It Li HW_MACHINE
201The machine class.
202.It Li HW_MODEL
203The machine model
204.It Li HW_NCPU
205The number of cpus.
206.It Li HW_BYTEORDER
207The byteorder (4,321, or 1,234).
208.It Li HW_PHYSMEM
209The bytes of physical memory.
210.It Li HW_USERMEM
211The bytes of non-kernel memory.
212.It Li HW_PAGESIZE
213The software page size.
214.\".It Fa HW_DISKNAMES
215.\".It Fa HW_DISKSTATS
216.El
217.Sh CTL_KERN
218The string and integer information available for the CTL_KERN level
219is detailed below.
220The changeable column shows whether a process with appropriate
221privilege may change the value.
222The types of data currently available are process information,
223system vnodes, the open file entries, routing table entries,
224virtual memory statistics, load average history, and clock rate
225information.
226.Bl -column "KERNXCHOWNXRESTRICTEDXXX" "struct clockrateXXX" -offset indent
227.It Sy Pa Second level name	Type	Changeable
228.It KERN\_ARGMAX	integer	no
229.It KERN\_BOOTTIME	struct timeval	no
230.It KERN\_CHOWN\_RESTRICTED	integer	no
231.It KERN\_CLOCKRATE	struct clockinfo	no
232.It KERN\_FILE	struct file	no
233.It KERN\_HOSTID	integer	yes
234.It KERN\_HOSTNAME	string	yes
235.It KERN\_JOB\_CONTROL	integer	no
236.It KERN\_LINK\_MAX	integer	no
237.It KERN\_MAXFILES	integer	yes
238.It KERN\_MAXPROC	integer	yes
239.It KERN\_MAXVNODES	integer	yes
240.It KERN\_MAX\_CANON	integer	no
241.It KERN\_MAX\_INPUT	integer	no
242.It KERN\_NAME\_MAX	integer	no
243.It KERN\_NGROUPS	integer	no
244.It KERN\_NO\_TRUNC	integer	no
245.It KERN\_OSRELEASE	string	no
246.It KERN\_OSREV	integer	no
247.It KERN\_OSTYPE	string	no
248.It KERN\_PATH\_MAX	integer	no
249.It KERN\_PIPE\_BUF	integer	no
250.It KERN\_POSIX1	integer	no
251.It KERN\_PROC	struct proc	no
252.It KERN\_PROF	node	not applicable
253.It KERN\_SAVED\_IDS	integer	no
254.It KERN\_SECURELVL	integer	raise only
255.It KERN\_VDISABLE	integer	no
256.It KERN\_VERSION	string	no
257.It KERN\_VNODE	struct vnode	no
258.El
259.Pp
260.Bl -tag -width "123456"
261.It Li KERN_ARGMAX
262The maximum bytes of argument to
263.Xr execve 2 .
264.It Li KERN_BOOTTIME
265A
266.Va struct timeval
267structure is returned.
268This structure contains the time that the system was booted.
269.It Li KERN_CHOWN_RESTRICTED
270Return 1 if appropriate privileges are required for the
271.Xr chown 2
272system call, otherwise 0.
273.It Li KERN_CLOCKRATE
274A
275.Va struct clockinfo
276structure is returned.
277This structure contains the clock, statistics clock and profiling clock
278frequencies, and the number of micro-seconds per hz tick.
279.It Li KERN_FILE
280Return the entire file table.
281The returned data consists of a single
282.Va struct filehead
283followed by an array of
284.Va struct file ,
285whose size depends on the current number of such objects in the system.
286.It Li KERN_HOSTID
287Get or set the host id.
288.It Li KERN_HOSTNAME
289Get or set the hostname.
290.It Li KERN_JOB_CONTROL
291Return 1 if job control is available on this system, otherwise 0.
292.It Li KERN_LINK_MAX
293The maximum file link count.
294.It Li KERN_MAXFILES
295The maximum number of open files that may be open in the system.
296.It Li KERN_MAXPROC
297The maximum number of simultaneous processes the system will allow.
298.It Li KERN_MAXVNODES
299The maximum number of vnodes available on the system.
300.It Li KERN_MAX_CANON
301The maximum number of bytes in terminal canonical input line.
302.It Li KERN_MAX_INPUT
303The minimum maximum number of bytes for which space is available in
304a terminal input queue.
305.It Li KERN_NAME_MAX
306The maximum number of bytes in a file name.
307.It Li KERN_NGROUPS
308The maximum number of supplemental groups.
309.It Li KERN_NO_TRUNC
310Return 1 if file names longer than KERN_NAME_MAX are truncated.
311.It Li KERN_OSRELEASE
312The system release string.
313.It Li KERN_OSREV
314The system revision string.
315.It Li KERN_OSTYPE
316The system type string.
317.It Li KERN_PATH_MAX
318The maximum number of bytes in a pathname.
319.It Li KERN_PIPE_BUF
320The maximum number of bytes which will be written atomically to a pipe.
321.It Li KERN_POSIX1
322The version of ISO/IEC 9945 (POSIX 1003.1) with which the system
323attempts to comply.
324.It Li KERN_PROC
325Return the entire process table, or a subset of it.
326An array of
327.Va struct kinfo_proc
328structures is returned,
329whose size depends on the current number of such objects in the system.
330The third and fourth level names are as follows:
331.Bl -column "Third level nameXXXXXX" "Fourth level is:XXXXXX" -offset indent
332.It Pa Third level name	Fourth level is:
333.It KERN\_PROC\_ALL	None
334.It KERN\_PROC\_PID	A process ID
335.It KERN\_PROC\_PGRP	A process group
336.It KERN\_PROC\_TTY	A tty device
337.It KERN\_PROC\_UID	A user ID
338.It KERN\_PROC\_RUID	A real user ID
339.El
340.It Li KERN_PROF
341Return profiling information about the kernel.
342If the kernel is not compiled for profiling,
343attempts to retrieve any of the KERN_PROF values will
344fail with EOPNOTSUPP.
345The third level names for the string and integer profiling information
346is detailed below.
347The changeable column shows whether a process with appropriate
348privilege may change the value.
349.Bl -column "GPROFXGMONPARAMXXX" "struct gmonparamXXX" -offset indent
350.It Sy Pa Third level name	Type	Changeable
351.It GPROF\_STATE	integer	yes
352.It GPROF\_COUNT	u_short[\|]	yes
353.It GPROF\_FROMS	u_short[\|]	yes
354.It GPROF\_TOS	struct tostruct	yes
355.It GPROF\_GMONPARAM	struct gmonparam	no
356.El
357.Pp
358The variables are as follows:
359.Bl -tag -width "123456"
360.It Li GPROF_STATE
361Returns GMON_PROF_ON or GMON_PROF_OFF to show that profiling
362is running or stopped.
363.It Li GPROF_COUNT
364Array of statistical program counter counts.
365.It Li GPROF_FROMS
366Array indexed by program counter of call-from points.
367.It Li GPROF_TOS
368Array of
369.Va struct tostruct
370describing destination of calls and their counts.
371.It Li GPROF_GMONPARAM
372Structure giving the sizes of the above arrays.
373.El
374.It Li KERN_SAVED_IDS
375Returns 1 if saved set-group and saved set-user ID is available.
376.It Li KERN_SECURELVL
377The system security level.
378This level may be raised by processes with appropriate privilege.
379It may only be lowered by process 1.
380.It Li KERN_VDISABLE
381Returns the terminal character disabling value.
382.It Li KERN_VERSION
383The system version string.
384.It Li KERN_VNODE
385Return the entire vnode table.
386Note, the vnode table is not necessarily a consistent snapshot of
387the system.
388The returned data consists of an array whose size depends on the
389current number of such objects in the system.
390Each element of the array contains the kernel address of a vnode
391.Va struct vnode *
392followed by the vnode itself
393.Va struct vnode .
394.El
395.Sh CTL_MACHDEP
396The set of variables defined is architecture dependent.
397Most architectures define at least the following variables.
398.Bl -column "CONSOLE_DEVICEXXX" "integerXXX" -offset indent
399.It Sy Pa Second level name	Type	Changeable
400.It Li CPU_CONSDEV	dev_t	no
401.It Li CPU_ADJKERNTZ	int	yes
402.It Li CPU_DISRTCSET	int	yes
403.El
404.Sh CTL_NET
405The string and integer information available for the CTL_NET level
406is detailed below.
407The changeable column shows whether a process with appropriate
408privilege may change the value.
409.Bl -column "Second level nameXXXXXX" "routing messagesXXX" -offset indent
410.It Sy Pa Second level name	Type	Changeable
411.It PF\_ROUTE	routing messages	no
412.It PF\_INET	internet values	yes
413.El
414.Pp
415.Bl -tag -width "123456"
416.It Li PF_ROUTE
417Return the entire routing table or a subset of it.
418The data is returned as a sequence of routing messages (see
419.Xr route 4
420for the header file, format and meaning).
421The length of each message is contained in the message header.
422.Pp
423The third level name is a protocol number, which is currently always 0.
424The fourth level name is an address family, which may be set to 0 to
425select all address families.
426The fifth and sixth level names are as follows:
427.Bl -column "Fifth level nameXXXXXX" "Sixth level is:XXX" -offset indent
428.It Pa Fifth level name	Sixth level is:
429.It NET\_RT\_FLAGS	rtflags
430.It NET\_RT\_DUMP	None
431.It NET\_RT\_IFLIST	None
432.El
433.It Li PF_INET
434Get or set various global information about the internet protocols.
435The third level name is the protocol.
436The fourth level name is the variable name.
437The currently defined protocols and names are:
438.Bl -column "Protocol nameXXXXXX" "Variable nameXXX" "integerXXX" -offset indent
439.It Pa Protocol name	Variable name	Type	Changeable
440.It ip	forwarding	integer	yes
441.It ip	redirect	integer	yes
442.It ip	ttl	integer	yes
443.It icmp	maskrepl	integer	yes
444.It udp	checksum	integer	yes
445.El
446.Pp
447The variables are as follows:
448.Bl -tag -width "123456"
449.It Li ip.forwarding
450Returns 1 when IP forwarding is enabled for the host,
451meaning that the host is acting as a router.
452.It Li ip.redirect
453Returns 1 when ICMP redirects may be sent by the host.
454This option is ignored unless the host is routing IP packets,
455and should normally be enabled on all systems.
456.It Li ip.ttl
457The maximum time-to-live (hop count) value for an IP packet sourced by
458the system.
459This value applies to normal transport protocols, not to ICMP.
460.It Li icmp.maskrepl
461Returns 1 if ICMP network mask requests are to be answered.
462.It Li udp.checksum
463Returns 1 when UDP checksums are being computed and checked.
464Disabling UDP checksums is strongly discouraged.
465.El
466.Sh CTL_USER
467The string and integer information available for the CTL_USER level
468is detailed below.
469The changeable column shows whether a process with appropriate
470privilege may change the value.
471.Bl -column "USER_COLL_WEIGHTS_MAXXXX" "integerXXX" -offset indent
472.It Sy Pa Second level name	Type	Changeable
473.It USER\_BC\_BASE\_MAX	integer	no
474.It USER\_BC\_DIM\_MAX	integer	no
475.It USER\_BC\_SCALE\_MAX	integer	no
476.It USER\_BC\_STRING\_MAX	integer	no
477.It USER\_COLL\_WEIGHTS\_MAX	integer	no
478.It USER\_CS\_PATH	string	no
479.It USER\_EXPR\_NEST\_MAX	integer	no
480.It USER\_LINE\_MAX	integer	no
481.It USER\_POSIX2\_CHAR\_TERM	integer	no
482.It USER\_POSIX2\_C\_BIND	integer	no
483.It USER\_POSIX2\_C\_DEV	integer	no
484.It USER\_POSIX2\_FORT\_DEV	integer	no
485.It USER\_POSIX2\_FORT\_RUN	integer	no
486.It USER\_POSIX2\_LOCALEDEF	integer	no
487.It USER\_POSIX2\_SW\_DEV	integer	no
488.It USER\_POSIX2\_UPE	integer	no
489.It USER\_POSIX2\_VERSION	integer	no
490.It USER\_RE\_DUP\_MAX	integer	no
491.It USER\_STREAM\_MAX	integer	no
492.It USER\_TZNAME\_MAX	integer	no
493.El
494.Bl -tag -width "123456"
495.Pp
496.It Li USER_BC_BASE_MAX
497The maximum ibase/obase values in the
498.Xr bc 1
499utility.
500.It Li USER_BC_DIM_MAX
501The maximum array size in the
502.Xr bc 1
503utility.
504.It Li USER_BC_SCALE_MAX
505The maximum scale value in the
506.Xr bc 1
507utility.
508.It Li USER_BC_STRING_MAX
509The maximum string length in the
510.Xr bc 1
511utility.
512.It Li USER_COLL_WEIGHTS_MAX
513The maximum number of weights that can be assigned to any entry of
514the LC_COLLATE order keyword in the locale definition file.
515.It Li USER_CS_PATH
516Return a value for the
517.Ev PATH
518environment variable that finds all the standard utilities.
519.It Li USER_EXPR_NEST_MAX
520The maximum number of expressions that can be nested within
521parenthesis by the
522.Xr expr 1
523utility.
524.It Li USER_LINE_MAX
525The maximum length in bytes of a text-processing utility's input
526line.
527.It Li USER_POSIX2_CHAR_TERM
528Return 1 if the system supports at least one terminal type capable of
529all operations described in POSIX 1003.2, otherwise 0.
530.It Li USER_POSIX2_C_BIND
531Return 1 if the system's C-language development facilities support the
532C-Language Bindings Option, otherwise 0.
533.It Li USER_POSIX2_C_DEV
534Return 1 if the system supports the C-Language Development Utilities Option,
535otherwise 0.
536.It Li USER_POSIX2_FORT_DEV
537Return 1 if the system supports the FORTRAN Development Utilities Option,
538otherwise 0.
539.It Li USER_POSIX2_FORT_RUN
540Return 1 if the system supports the FORTRAN Runtime Utilities Option,
541otherwise 0.
542.It Li USER_POSIX2_LOCALEDEF
543Return 1 if the system supports the creation of locales, otherwise 0.
544.It Li USER_POSIX2_SW_DEV
545Return 1 if the system supports the Software Development Utilities Option,
546otherwise 0.
547.It Li USER_POSIX2_UPE
548Return 1 if the system supports the User Portability Utilities Option,
549otherwise 0.
550.It Li USER_POSIX2_VERSION
551The version of POSIX 1003.2 with which the system attempts to comply.
552.It Li USER_RE_DUP_MAX
553The maximum number of repeated occurrences of a regular expression
554permitted when using interval notation.
555.It Li USER_STREAM_MAX
556The minimum maximum number of streams that a process may have open
557at any one time.
558.It Li USER_TZNAME_MAX
559The minimum maximum number of types supported for the name of a
560timezone.
561.El
562.Sh CTL_VM
563The string and integer information available for the CTL_VM level
564is detailed below.
565The changeable column shows whether a process with appropriate
566privilege may change the value.
567.Bl -column "Second level nameXXXXXX" "struct loadavgXXX" -offset indent
568.It Sy Pa Second level name	Type	Changeable
569.It VM\_LOADAVG	struct loadavg	no
570.It VM\_METER	struct vmtotal	no
571.El
572.Pp
573.Bl -tag -width "123456"
574.It Li VM_LOADAVG
575Return the load average history.
576The returned data consists of a
577.Va struct loadavg .
578.It Li VM_METER
579Return the system wide virtual memory statistics.
580The returned data consists of a
581.Va struct vmtotal .
582.El
583.Sh RETURN VALUES
584If the call to
585.Nm sysctl
586is successful, 0 is returned.
587Otherwise \-1 is returned and
588.Va errno
589is set appropriately.
590.Sh ERRORS
591The following errors may be reported:
592.Bl -tag -width Er
593.It Bq Er EFAULT
594The buffer
595.Fa name ,
596.Fa oldp ,
597.Fa newp ,
598or length pointer
599.Fa oldlenp
600contains an invalid address.
601.It Bq Er EINVAL
602The
603.Fa name
604array is less than two or greater than CTL_MAXNAME.
605.It Bq Er EINVAL
606A non-null
607.Fa newp
608is given and its specified length in
609.Fa newlen
610is too large or too small.
611.It Bq Er ENOMEM
612The length pointed to by
613.Fa oldlenp
614is too short to hold the requested value.
615.It Bq Er ENOTDIR
616The
617.Fa name
618array specifies an intermediate rather than terminal name.
619.It Bq Er EOPNOTSUPP
620The
621.Fa name
622array specifies a value that is unknown.
623.It Bq Er EPERM
624An attempt is made to set a read-only value.
625.It Bq Er EPERM
626A process without appropriate privilege attempts to set a value.
627.El
628.Sh FILES
629.Bl -tag -width <netinet/icmpXvar.h> -compact
630.It Pa <sys/sysctl.h>
631definitions for top level identifiers, second level kernel and hardware
632identifiers, and user level identifiers
633.It Pa <sys/socket.h>
634definitions for second level network identifiers
635.It Pa <sys/gmon.h>
636definitions for third level profiling identifiers
637.It Pa <vm/vm_param.h>
638definitions for second level virtual memory identifiers
639.It Pa <netinet/in.h>
640definitions for third level Internet identifiers and
641fourth level IP identifiers
642.It Pa <netinet/icmp_var.h>
643definitions for fourth level ICMP identifiers
644.It Pa <netinet/udp_var.h>
645definitions for fourth level UDP identifiers
646.El
647.Sh SEE ALSO
648.Xr sysctl 8
649.Sh HISTORY
650The
651.Nm sysctl
652function first appeared in 4.4BSD.
653