xref: /openbsd/sbin/sysctl/sysctl.8 (revision 9b7c3dbb) 
1.\"	$OpenBSD: sysctl.8,v 1.204 2016/07/27 20:51:46 tedu Exp $
2.\"	$NetBSD: sysctl.8,v 1.4 1995/09/30 07:12:49 thorpej Exp $
3.\"
4.\" Copyright (c) 1993
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31.\"	@(#)sysctl.8	8.2 (Berkeley) 5/9/95
32.\"
33.Dd $Mdocdate: July 27 2016 $
34.Dt SYSCTL 8
35.Os
36.Sh NAME
37.Nm sysctl
38.Nd get or set kernel state
39.Sh SYNOPSIS
40.Nm sysctl
41.Op Fl Aan
42.Nm sysctl
43.Op Fl n
44.Ar name ...
45.Nm sysctl
46.Op Fl nq
47.Ar name Ns = Ns Ar value ...
48.Sh DESCRIPTION
49The
50.Nm
51utility retrieves kernel state and allows processes with
52appropriate privilege to set kernel state.
53The state to be retrieved or set is described using a
54.Dq Management Information Base
55.Pq MIB
56style name, described as a dotted set of components.
57.Pp
58When retrieving a variable,
59a subset of the MIB name may be specified to retrieve a list of
60variables in that subset.
61For example, to list all the machdep variables:
62.Pp
63.Dl $ sysctl machdep
64.Pp
65When setting a variable,
66the MIB name should be followed by an equal sign and the new value.
67.Pp
68The options are as follows:
69.Bl -tag -width xxx
70.It Fl A
71List all the known MIB names including tables.
72Those with string or integer values will be printed as with the
73.Fl a
74flag; for the table values, the name of the utility to retrieve them is given.
75.It Fl a
76List all the currently available string or integer values.
77This is the default, if no parameters are given to
78.Nm .
79.It Fl n
80Suppress printing of the field name, only output the field value.
81Useful for setting shell variables.
82For example, to set the psize shell variable to the pagesize of the hardware:
83.Pp
84.Dl # set psize=`sysctl -n hw.pagesize`
85.It Fl q
86Suppress all output when setting a variable.
87This option overrides the behaviour of
88.Fl n .
89.It Ar name Ns = Ns Ar value
90Attempt to set the specified variable
91.Ar name
92to
93.Ar value .
94.El
95.Pp
96The information available from
97.Nm
98consists of integers, strings, and tables.
99The tabular information can only be retrieved by special
100purpose programs such as
101.Xr ps 1 ,
102.Xr systat 1 ,
103and
104.Xr netstat 1 .
105The string and integer information is summarized below.
106For a detailed description of these variables, see
107.Xr sysctl 3 .
108The changeable column indicates whether a process with appropriate
109privilege can change the value.
110.Pp
111Note:
112not all of the variables are relevant to all architectures,
113and a few require a kernel compiled with non-standard
114.Xr options 4 .
115.Bl -column "kern.timecounter.timestepwarnings" "integer" "Changeable"
116.It Sy Name Ta Sy Type Ta Sy Changeable
117.It kern.ostype	string	no
118.It kern.osrelease Ta string Ta no
119.It kern.osrevision Ta integer Ta no
120.It kern.version Ta string Ta no
121.It kern.maxvnodes Ta integer Ta yes
122.It kern.maxproc Ta integer Ta yes
123.It kern.maxfiles Ta integer Ta yes
124.It kern.argmax Ta integer Ta no
125.It kern.securelevel Ta integer Ta raise only
126.It kern.hostname Ta string Ta yes
127.It kern.hostid Ta u_int Ta yes
128.It kern.clockrate Ta struct Ta no
129.It kern.posix1version Ta integer Ta no
130.It kern.ngroups Ta integer Ta no
131.It kern.job_control Ta integer Ta no
132.It kern.saved_ids Ta integer Ta no
133.It kern.boottime Ta struct Ta no
134.It kern.domainname Ta string Ta yes
135.It kern.maxpartitions Ta integer Ta no
136.It kern.rawpartition Ta integer Ta no
137.It kern.maxthread Ta integer Ta yes
138.It kern.nthreads Ta integer Ta no
139.It kern.osversion Ta string Ta no
140.It kern.somaxconn Ta integer Ta yes
141.It kern.sominconn Ta integer Ta yes
142.It kern.usermount Ta integer Ta yes
143.It kern.nosuidcoredump Ta integer Ta yes
144.It kern.fsync Ta integer Ta no
145.It kern.sysvmsg Ta integer Ta no
146.It kern.sysvsem Ta integer Ta no
147.It kern.sysvshm Ta integer Ta no
148.It kern.arandom Ta u_int Ta no
149.It kern.msgbufsize Ta integer Ta no
150.It kern.malloc.buckets Ta string Ta no
151.It kern.malloc.bucket.<sz> Ta string Ta no
152.It kern.malloc.kmemnames Ta string Ta no
153.It kern.malloc.kmemstat.<name> Ta string Ta no
154.It kern.cp_time Ta struct Ta no
155.It kern.nchstats Ta struct Ta no
156.It kern.forkstat Ta struct Ta no
157.It kern.nselcoll Ta integer Ta no
158.It kern.tty.tk_nin Ta int64_t Ta no
159.It kern.tty.tk_nout Ta int64_t Ta no
160.It kern.tty.tk_rawcc Ta int64_t Ta no
161.It kern.tty.tk_cancc Ta int64_t Ta no
162.It kern.tty.ttyinfo Ta struct Ta no
163.It kern.ccpu Ta u_int Ta no
164.It kern.fscale Ta integer Ta no
165.It kern.nprocs Ta integer Ta no
166.It kern.stackgap_random Ta integer Ta yes
167.It kern.splassert Ta integer Ta yes
168.It kern.nfiles Ta integer Ta no
169.It kern.ttycount Ta integer Ta no
170.It kern.numvnodes Ta integer Ta no
171.It kern.seminfo.semmni Ta integer Ta yes
172.It kern.seminfo.semmns Ta integer Ta yes
173.It kern.seminfo.semmnu Ta integer Ta yes
174.It kern.seminfo.semmsl Ta integer Ta yes
175.It kern.seminfo.semopm Ta integer Ta yes
176.It kern.seminfo.semume Ta integer Ta no
177.It kern.seminfo.semusz Ta integer Ta no
178.It kern.seminfo.semvmx Ta integer Ta no
179.It kern.seminfo.semaem Ta integer Ta no
180.It kern.shminfo.shmmax Ta integer Ta yes
181.It kern.shminfo.shmmin Ta integer Ta yes
182.It kern.shminfo.shmmni Ta integer Ta yes
183.It kern.shminfo.shmseg Ta integer Ta yes
184.It kern.shminfo.shmall Ta integer Ta yes
185.It kern.watchdog.period Ta integer Ta yes
186.It kern.watchdog.auto Ta integer Ta yes
187.It kern.maxclusters Ta integer Ta yes
188.It kern.timecounter.tick Ta integer Ta no
189.It kern.timecounter.timestepwarnings Ta integer Ta yes
190.It kern.timecounter.hardware Ta string Ta yes
191.It kern.timecounter.choice Ta string Ta no
192.It kern.maxlocksperuid Ta integer Ta yes
193.It kern.bufcachepercent Ta integer Ta yes
194.It kern.wxabort Ta integer Ta yes
195.It kern.consdev Ta string Ta no
196.It kern.global_ptrace Ta integer Ta yes
197.It vm.vmmeter Ta struct Ta no
198.It vm.loadavg Ta struct Ta no
199.It vm.psstrings Ta struct Ta no
200.It vm.uvmexp Ta struct Ta no
201.It vm.swapencrypt.enable Ta integer Ta yes
202.It vm.swapencrypt.keyscreated Ta integer Ta no
203.It vm.swapencrypt.keysdeleted Ta integer Ta no
204.It vm.nkmempages Ta integer Ta no
205.It vm.anonmin Ta integer Ta yes
206.It vm.vtextmin Ta integer Ta yes
207.It vm.vnodemin Ta integer Ta yes
208.It vm.maxslp Ta integer Ta no
209.It vm.uspace Ta integer Ta no
210.It fs.posix.setuid Ta integer Ta yes
211.It net.inet.divert.recvspace Ta integer Ta yes
212.It net.inet.divert.sendspace Ta integer Ta yes
213.It net.inet.ip.forwarding Ta integer Ta yes
214.It net.inet.ip.redirect Ta integer Ta yes
215.It net.inet.ip.ttl Ta integer Ta yes
216.\" .It net.inet.ip.mtu Ta integer Ta yes
217.It net.inet.ip.sourceroute Ta integer Ta yes
218.It net.inet.ip.directed-broadcast Ta integer Ta yes
219.It net.inet.ip.portfirst Ta integer Ta yes
220.It net.inet.ip.portlast Ta integer Ta yes
221.It net.inet.ip.porthifirst Ta integer Ta yes
222.It net.inet.ip.porthilast Ta integer Ta yes
223.It net.inet.ip.maxqueue Ta integer Ta yes
224.It net.inet.ip.encdebug Ta integer Ta yes
225.It net.inet.ip.ipsec-expire-acquire Ta integer Ta yes
226.It net.inet.ip.ipsec-invalid-life Ta integer Ta yes
227.It net.inet.ip.ipsec-pfs Ta integer Ta yes
228.It net.inet.ip.ipsec-soft-allocs Ta integer Ta yes
229.It net.inet.ip.ipsec-allocs Ta integer Ta yes
230.It net.inet.ip.ipsec-soft-bytes Ta integer Ta yes
231.It net.inet.ip.ipsec-bytes Ta integer Ta yes
232.It net.inet.ip.ipsec-timeout Ta integer Ta yes
233.It net.inet.ip.ipsec-soft-timeout Ta integer Ta yes
234.It net.inet.ip.ipsec-soft-firstuse Ta integer Ta yes
235.It net.inet.ip.ipsec-firstuse Ta integer Ta yes
236.It net.inet.ip.ipsec-enc-alg Ta string Ta yes
237.It net.inet.ip.ipsec-auth-alg Ta string Ta yes
238.It net.inet.ip.mtudisc Ta integer Ta yes
239.It net.inet.ip.mtudisctimeout Ta integer Ta yes
240.It net.inet.ip.ipsec-comp-alg Ta string Ta yes
241.It net.inet.ip.ifq.len Ta integer Ta no
242.It net.inet.ip.ifq.maxlen Ta integer Ta yes
243.It net.inet.ip.ifq.drops Ta integer Ta no
244.It net.inet.ip.mforwarding Ta integer Ta yes
245.It net.inet.ip.multipath Ta integer Ta yes
246.It net.inet.ip.arptimeout Ta integer Ta yes
247.It net.inet.ip.arpdown Ta integer Ta yes
248.It net.inet.icmp.maskrepl Ta integer Ta yes
249.It net.inet.icmp.bmcastecho Ta integer Ta yes
250.It net.inet.icmp.errppslimit Ta integer Ta yes
251.It net.inet.icmp.rediraccept Ta integer Ta yes
252.It net.inet.icmp.redirtimeout Ta integer Ta yes
253.It net.inet.icmp.tstamprepl Ta integer Ta yes
254.It net.inet.ipip.allow Ta integer Ta yes
255.It net.inet.tcp.rfc1323 Ta integer Ta yes
256.It net.inet.tcp.keepinittime Ta integer Ta yes
257.It net.inet.tcp.keepidle Ta integer Ta yes
258.It net.inet.tcp.keepintvl Ta integer Ta yes
259.It net.inet.tcp.slowhz Ta integer Ta no
260.It net.inet.tcp.baddynamic Ta array Ta yes
261.It net.inet.tcp.sack Ta integer Ta yes
262.It net.inet.tcp.mssdflt Ta integer Ta yes
263.It net.inet.tcp.rstppslimit Ta integer Ta yes
264.It net.inet.tcp.ackonpush Ta integer Ta yes
265.It net.inet.tcp.ecn Ta integer Ta yes
266.It net.inet.tcp.syncachelimit Ta integer Ta yes
267.It net.inet.tcp.synbucketlimit Ta integer Ta yes
268.It net.inet.tcp.rfc3390 Ta integer Ta yes
269.It net.inet.tcp.reasslimit Ta integer Ta yes
270.It net.inet.tcp.sackholelimit Ta integer Ta yes
271.It net.inet.tcp.always_keepalive Ta integer Ta yes
272.It net.inet.tcp.synuselimit Ta integer Ta yes
273.It net.inet.tcp.rootonly Ta array Ta yes
274.It net.inet.tcp.synhashsize Ta integer Ta yes
275.It net.inet.udp.checksum Ta integer Ta yes
276.It net.inet.udp.baddynamic Ta array Ta yes
277.It net.inet.udp.recvspace Ta integer Ta yes
278.It net.inet.udp.sendspace Ta integer Ta yes
279.It net.inet.udp.rootonly Ta array Ta yes
280.It net.inet.gre.allow Ta integer Ta yes
281.It net.inet.gre.wccp Ta integer Ta yes
282.It net.inet.esp.enable Ta integer Ta yes
283.It net.inet.esp.udpencap Ta integer Ta yes
284.It net.inet.esp.udpencap_port Ta integer Ta yes
285.It net.inet.ah.enable Ta integer Ta yes
286.It net.inet.mobileip.allow Ta integer Ta yes
287.It net.inet.etherip.allow Ta integer Ta yes
288.It net.inet.ipcomp.enable Ta integer Ta yes
289.It net.inet.carp.allow Ta integer Ta yes
290.It net.inet.carp.preempt Ta integer Ta yes
291.It net.inet.carp.log Ta integer Ta yes
292.It net.inet6.ip6.forwarding Ta integer Ta yes
293.It net.inet6.ip6.redirect Ta integer Ta yes
294.It net.inet6.ip6.hlim Ta integer Ta yes
295.It net.inet6.ip6.maxfragpackets Ta integer Ta yes
296.It net.inet6.ip6.log_interval Ta integer Ta yes
297.It net.inet6.ip6.hdrnestlimit Ta integer Ta yes
298.It net.inet6.ip6.dad_count Ta integer Ta yes
299.It net.inet6.ip6.auto_flowlabel Ta integer Ta yes
300.It net.inet6.ip6.defmcasthlim Ta integer Ta yes
301.It net.inet6.ip6.use_deprecated Ta integer Ta yes
302.It net.inet6.ip6.maxfrags Ta integer Ta yes
303.It net.inet6.ip6.mforwarding Ta integer Ta yes
304.It net.inet6.ip6.multipath Ta integer Ta yes
305.It net.inet6.ip6.multicast_mtudisc Ta integer Ta yes
306.It net.inet6.ip6.neighborgcthresh Ta integer Ta yes
307.It net.inet6.ip6.maxifprefixes Ta integer Ta yes
308.It net.inet6.ip6.maxifdefrouters Ta integer Ta yes
309.It net.inet6.ip6.maxdynroutes Ta integer Ta yes
310.It net.inet6.ip6.dad_pending Ta integer Ta yes
311.It net.inet6.ip6.mtudisctimeout Ta integer Ta yes
312.It net.inet6.ip6.ifq.len Ta integer Ta no
313.It net.inet6.ip6.ifq.maxlen Ta integer Ta yes
314.It net.inet6.ip6.ifq.drops Ta integer Ta no
315.It net.inet6.icmp6.redirtimeout Ta integer Ta yes
316.It net.inet6.icmp6.nd6_prune Ta integer Ta yes
317.It net.inet6.icmp6.nd6_delay Ta integer Ta yes
318.It net.inet6.icmp6.nd6_umaxtries Ta integer Ta yes
319.It net.inet6.icmp6.nd6_mmaxtries Ta integer Ta yes
320.It net.inet6.icmp6.errppslimit Ta integer Ta yes
321.It net.inet6.icmp6.nd6_maxnudhint Ta integer Ta yes
322.It net.inet6.icmp6.mtudisc_hiwat Ta integer Ta yes
323.It net.inet6.icmp6.mtudisc_lowat Ta integer Ta yes
324.It net.inet6.icmp6.nd6_debug Ta integer Ta yes
325.It net.mpls.ttl Ta integer Ta yes
326.It net.mpls.ifq.len Ta integer Ta no
327.It net.mpls.ifq.maxlen Ta integer Ta yes
328.It net.mpls.ifq.drops Ta integer Ta no
329.It net.mpls.maxloop_inkernel Ta integer Ta yes
330.It net.mpls.mapttl_ip Ta integer Ta yes
331.It net.mpls.mapttl_ip6 Ta integer Ta yes
332.It net.pipex.enable Ta integer Ta yes
333.It net.pipex.inq.len Ta integer Ta no
334.It net.pipex.inq.maxlen Ta integer Ta yes
335.It net.pipex.inq.drops Ta integer Ta no
336.It net.pipex.outq.len Ta integer Ta no
337.It net.pipex.outq.maxlen Ta integer Ta yes
338.It net.pipex.outq.drops=0 Ta integer Ta no
339.It debug.syncprt Ta integer Ta yes
340.It debug.busyprt Ta integer Ta yes
341.It hw.machine Ta string Ta no
342.It hw.model Ta string Ta no
343.It hw.ncpu Ta integer Ta no
344.It hw.byteorder Ta integer Ta no
345.It hw.physmem Ta int64_t Ta no
346.It hw.usermem Ta int64_t Ta no
347.It hw.pagesize Ta integer Ta no
348.It hw.diskstats Ta struct Ta no
349.It hw.disknames Ta string Ta no
350.It hw.diskcount Ta integer Ta no
351.It hw.sensors.<xname>.<type><numt> Ta struct Ta no
352.It hw.cpuspeed Ta integer Ta no
353.It hw.setperf Ta integer Ta yes
354.It hw.vendor Ta string Ta no
355.It hw.product Ta string Ta no
356.It hw.version Ta string Ta no
357.It hw.serialno Ta string Ta no
358.It hw.uuid Ta string Ta no
359.It hw.ncpufound Ta integer Ta no
360.It hw.allowpowerdown Ta integer Ta yes
361.It hw.perfpolicy Ta string Ta yes
362.It machdep.console_device Ta dev_t Ta no
363.It machdep.unaligned_print Ta integer Ta yes
364.It machdep.unaligned_fix Ta integer Ta yes
365.It machdep.unaligned_sigbus Ta integer Ta yes
366.It machdep.apmwarn Ta integer Ta yes
367.It machdep.apmhalt Ta integer Ta yes
368.It machdep.kbdreset Ta integer Ta yes
369.It machdep.osfxsr Ta integer Ta no
370.It machdep.sse Ta integer Ta no
371.It machdep.sse2 Ta integer Ta no
372.It machdep.xcrypt Ta integer Ta no
373.It machdep.allowaperture Ta integer Ta yes
374.It machdep.led_blink Ta integer Ta yes
375.It machdep.ceccerrs Ta integer Ta no
376.It machdep.cecclast Ta quad Ta no
377.It ddb.radix Ta integer Ta yes
378.It ddb.max_width Ta integer Ta yes
379.It ddb.max_line Ta integer Ta yes
380.It ddb.tab_stop_width Ta integer Ta yes
381.It ddb.panic Ta integer Ta yes
382.It ddb.console Ta integer Ta yes
383.It ddb.log Ta integer Ta yes
384.It ddb.trigger Ta integer Ta yes
385.It vfs.mounts.* Ta struct Ta no
386.It vfs.ffs.max_softdeps Ta integer Ta yes
387.It vfs.ffs.sd_tickdelay Ta integer Ta yes
388.It vfs.ffs.sd_worklist_push Ta integer Ta no
389.It vfs.ffs.sd_blk_limit_push Ta integer Ta no
390.It vfs.ffs.sd_ino_limit_push Ta integer Ta no
391.It vfs.ffs.sd_blk_limit_hit Ta integer Ta no
392.It vfs.ffs.sd_ino_limit_hit Ta integer Ta no
393.It vfs.ffs.sd_sync_limit_hit Ta integer Ta no
394.It vfs.ffs.sd_indir_blk_ptrs Ta integer Ta no
395.It vfs.ffs.sd_inode_bitmap Ta integer Ta no
396.It vfs.ffs.sd_direct_blk_ptrs Ta integer Ta no
397.It vfs.ffs.sd_dir_entry Ta integer Ta no
398.It vfs.ffs.dirhash_dirsize Ta integer Ta yes
399.It vfs.ffs.dirhash_maxmem Ta integer Ta yes
400.It vfs.ffs.dirhash_mem Ta integer Ta no
401.It vfs.nfs.iothreads Ta integer Ta yes
402.It vfs.fuse.fusefs_open_devices Ta integer Ta no
403.It vfs.fuse.fusefs_fbufs_in Ta integer Ta no
404.It vfs.fuse.fusefs_fbufs_wait Ta integer Ta no
405.It vfs.fuse.fusefs_pool_pages Ta integer Ta no
406.El
407.Pp
408The
409.Nm
410program can extract information about the filesystems that have been compiled
411into the running system.
412This information can be obtained by using the command:
413.Pp
414.Dl $ sysctl vfs.mounts
415.Pp
416By default, only filesystems that are actively being used are listed.
417Use of the
418.Fl A
419flag lists all the filesystems compiled into the running kernel.
420.Sh FILES
421.Bl -tag -width <uvm/uvm_swap_encrypt.h> -compact
422.It In sys/sysctl.h
423definitions for top level identifiers and second level kernel and hardware
424identifiers
425.It In sys/socket.h
426definitions for second level network identifiers
427.It In sys/gmon.h
428definitions for third level profiling identifiers
429.It In uvm/uvm_param.h
430definitions for second level virtual memory identifiers
431.It In uvm/uvm_swap_encrypt.h
432definitions for third level virtual memory identifiers
433.It In netinet/in.h
434definitions for third level IPv4/v6 identifiers and
435fourth level IPv4/v6 identifiers
436.It In netinet/ip_divert.h
437definitions for fourth level divert identifiers
438.It In netinet/icmp_var.h
439definitions for fourth level ICMP identifiers
440.It In netinet6/icmp6.h
441definitions for fourth level ICMPv6 identifiers
442.It In netinet/tcp_var.h
443definitions for fourth level TCP identifiers
444.It In netinet/udp_var.h
445definitions for fourth level UDP identifiers
446.It In ddb/db_var.h
447definitions for second level ddb identifiers
448.It In sys/mount.h
449definitions for second level vfs identifiers
450.It In nfs/nfs.h
451definitions for third level NFS identifiers
452.It In miscfs/fuse/fusefs.h
453definitions for third level fusefs identifiers
454.It In ufs/ffs/ffs_extern.h
455definitions for third level FFS identifiers
456.It In machine/cpu.h
457definitions for second level CPU identifiers
458.El
459.Sh EXAMPLES
460To retrieve the maximum number of processes allowed
461in the system:
462.Pp
463.Dl $ sysctl kern.maxproc
464.Pp
465To set the maximum number of processes allowed
466in the system to 1000:
467.Pp
468.Dl # sysctl kern.maxproc=1000
469.Pp
470To retrieve information about the system clock rate:
471.Pp
472.Dl $ sysctl kern.clockrate
473.Pp
474To retrieve information about the load average history:
475.Pp
476.Dl $ sysctl vm.loadavg
477.Pp
478To make the
479.Xr chown 2
480system call use traditional
481.Bx
482semantics (don't clear setuid/setgid bits):
483.Pp
484.Dl # sysctl fs.posix.setuid=0
485.Pp
486To set the list of reserved TCP ports that should not be allocated
487by the kernel dynamically:
488.Pp
489.Dl # sysctl net.inet.tcp.baddynamic=749,750,751,760,761,871
490.Dl # sysctl net.inet.udp.baddynamic=749,750,751,760,761,871,1024-2048
491.Pp
492This can be used to keep daemons
493from stealing a specific port that another program needs to function.
494List elements may be separated by commas and/or whitespace;
495a hyphen may be used to specify a range of ports.
496.Pp
497It is also possible to add or remove ports from the current list:
498.Bd -literal -offset indent
499# sysctl net.inet.tcp.baddynamic=+748,+6000-6999
500# sysctl net.inet.tcp.baddynamic=-871
501.Ed
502.Pp
503To set the amount of shared memory available in the system and
504the maximum number of shared memory segments:
505.Bd -literal -offset indent
506# sysctl kern.shminfo.shmmax=33554432
507# sysctl kern.shminfo.shmseg=32
508.Ed
509.Pp
510To place core dumps from
511.Xr issetugid 2
512programs (in this example
513.Xr bgpd 8 )
514into a safe place for debugging purposes:
515.Bd -literal -offset indent
516# mkdir -m 700 /var/crash/bgpd
517# sysctl kern.nosuidcoredump=3
518.Ed
519.Sh SEE ALSO
520.Xr sysctl 3 ,
521.Xr options 4 ,
522.Xr sysctl.conf 5
523.Sh HISTORY
524.Nm
525first appeared in
526.Bx 4.4 .
527