1.\" $OpenBSD: options.4,v 1.231 2013/03/22 16:40:24 deraadt Exp $ 2.\" $NetBSD: options.4,v 1.21 1997/06/25 03:13:00 thorpej Exp $ 3.\" 4.\" Copyright (c) 1998 Theo de Raadt 5.\" Copyright (c) 1998 Todd Miller 6.\" Copyright (c) 1998 Gene Skonicki 7.\" Copyright (c) 1996 8.\" Perry E. Metzger. All rights reserved. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. All advertising materials mentioning features or use of this software 19.\" must display the following acknowledgment: 20.\" This product includes software developed for the NetBSD Project 21.\" by Perry E. Metzger. 22.\" 4. The name of the author may not be used to endorse or promote products 23.\" derived from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 26.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 29.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 30.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 31.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 32.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 33.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 34.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35.\" 36.\" 37.Dd $Mdocdate: March 22 2013 $ 38.Dt OPTIONS 4 39.Os 40.Sh NAME 41.Nm options 42.Nd kernel configuration options 43.Sh SYNOPSIS 44.Cd option ... 45.Sh DESCRIPTION 46This manual page describes a number of miscellaneous kernel 47configuration options that may be specified in a kernel config file. 48See 49.Xr config 8 50for information on how to configure and build kernels. 51.Em Note: 52options are passed to the compile process as 53.Fl D 54flags to the C compiler. 55.Sh COMPATIBILITY OPTIONS 56.Bl -ohang 57.It Cd option COMPAT_43 58This option enables compatibility with 59.Bx 4.3 . 60It adds ioctls for 61.Dv TIOCGETP 62and 63.Dv TIOCSETP . 64It also enables the deprecated 65.Dv NTTYDISC 66terminal line discipline. 67It provides backwards compatibility with the 68.Dq old 69SIOC[GS]IF{ADDR,DSTADDR,BRDADDR,NETMASK} interface ioctls, including 70binary compatibility for code written before the introduction of the 71.Li sa_len 72field in sockaddrs. 73.It Cd option COMPAT_LINUX 74On those architectures that support it, this enables binary 75compatibility with 76.Em Linux 77ELF and a.out 78applications built for the same architecture. 79This option is supported on the i386 architecture. 80See 81.Xr compat_linux 8 . 82.El 83.Sh DEBUGGING OPTIONS 84.Bl -ohang 85.It Cd makeoptions DEBUG="-g" 86The 87.Fl g 88flag causes 89.Pa bsd.gdb 90to be built in addition to 91.Pa bsd . 92.Pa bsd.gdb 93is useful for debugging kernels and their crash dumps with gdb. 94A crash dump can be debugged by starting 95.Xr gdb 1 96with the kernel name 97.Pf ( Pa bsd.gdb ) 98as an argument (no core file) and then use the 99.Xr gdb 1 100command 101.Dq target kvm COREFILE . 102.It Cd makeoptions PROF="-pg" 103The 104.Fl pg 105flag causes the kernel to be compiled with support for profiling. 106The 107.Cm option GPROF 108is required for the kernel compile to succeed. 109.It Cd option ACCOUNTING 110Adds support for the 111.Xr acct 2 112system call. 113.It Cd option DDB 114Compiles in a kernel debugger for diagnosing kernel problems. 115See 116.Xr ddb 4 117for details. 118.It Cd option DDB_SAFE_CONSOLE 119Allows a break into the kernel debugger during boot. 120Useful when debugging problems that can cause 121.Xr init 8 122to fail. 123.It Cd option DDB_STRUCT 124Compiles in symbolic information about the various data structures used by the 125kernel, for use within the kernel debugger. 126This option is currently not supported on alpha, m68k, m88k and vax based 127platforms. 128.It Cd option DEBUG 129Turns on miscellaneous kernel debugging. 130Since options are turned into preprocessor defines (see above), 131.Cm option DEBUG 132is equivalent to doing a 133.Em #define DEBUG 134throughout the kernel. 135Much of the kernel has 136.Em #ifdef DEBUG 137conditional debugging code. 138Note that many parts of the kernel (typically device drivers) include their own 139.Em #ifdef XXX_DEBUG 140conditionals instead. 141This option also turns on certain other options, notably 142.Cm option KMEMSTATS . 143.It Cd option DIAGNOSTIC 144Adds code to the kernel that does internal consistency checks. 145This code will cause the kernel to panic if corruption of internal data 146structures is detected. 147.It Cd option GPROF 148Adds code to the kernel for kernel profiling with 149.Xr kgmon 8 . 150.It Cd option KGDB 151Compiles in a remote kernel debugger stub for diagnosing kernel problems 152using the 153.Dq remote target 154feature of gdb. 155See 156.Xr kgdb 7 157for details. 158.Em Note: 159not available on all architectures. 160.It Cd option KTRACE 161Adds hooks for the system call tracing facility, which allows users to 162watch the system call invocation behavior of processes. 163See 164.Xr ktrace 1 165for details. 166.It Cd option NO_PROPOLICE 167Do not compile the kernel with the ProPolice stack protection. 168See 169.Xr gcc-local 1 170for more information about ProPolice. 171.It Cd option PTRACE 172Adds hooks for the process tracing facility, allowing a process to 173control and observe another process. 174See 175.Xr ptrace 2 176for details. 177.It Cd option SMALL_KERNEL 178Removes some features and some optimizations from the kernel to reduce the 179size of the resulting kernel binary. 180This option is used on some installation media and should not be used 181for general purpose kernels. 182.It Cd option VFSLCKDEBUG 183Turns on debugging for the Virtual File System interface. 184See 185.Xr vfs 9 186for details. 187.El 188.Sh FILE SYSTEMS 189.Bl -ohang 190.It Cd option CD9660 191Includes code for the ISO 9660 + Rock Ridge file system, which is the 192standard file system used on many CD-ROMs. 193It also supports Joliet extensions. 194See 195.Xr mount_cd9660 8 196for details. 197.It Cd option EXT2FS 198Includes code implementing the Second Extended File System 199.Em ( EXT2FS ) , 200commonly used on the Linux operating system. 201This option is provided here for compatibility. 202Some specific features of 203.Em EXT2FS 204like the "behavior on errors" are not implemented. 205This file system 206can't be used with 207.Li uid_t 208or 209.Li gid_t 210values greater than 65535. 211Also, the filesystem will not function correctly on architectures with 212differing byte-orders. 213That is, a big-endian machine will not be able to read an 214ext2fs filesystem created on an i386 or other little-endian machine. 215See 216.Xr mount_ext2fs 8 217for details. 218.It Cd option FFS 219Includes code implementing the Berkeley Fast File System 220.Em ( FFS ) . 221Most machines need this if they are not running diskless. 222.It Cd option FFS2 223Includes code implementing the enhanced Fast File System 224.Em ( FFS2 ) . 225.It Cd option MFS 226Include the memory file system 227.Em ( MFS ) . 228This file system stores files in swappable memory, and produces 229notable performance improvements when it is used as the file store 230for 231.Pa /tmp 232or similar mount points. 233See 234.Xr mount_mfs 8 235for details. 236.It Cd option MSDOSFS 237Includes support for the MS-DOS FAT file system. 238The kernel also implements the Windows 95 239extensions which permit the use of longer, mixed-case file names. 240See 241.Xr mount_msdos 8 242and 243.Xr fsck_msdos 8 244for details. 245.It Cd option NFSCLIENT 246Include the client side of the 247.Em NFS 248(Network File System) remote file sharing protocol. 249Although the bulk of the code implementing 250.Em NFS 251is kernel based, several user level daemons are needed for it to work. 252See 253.Xr mount_nfs 8 254for details on NFS. 255.It Cd option NTFS 256Includes support for reading NTFS file systems. 257See 258.Xr mount_ntfs 8 259for details. 260.It Cd option PROCFS 261Includes code for a special file system (conventionally mounted on 262.Pa /proc ) 263in which the process space becomes visible in the file system. 264Among other things, the memory spaces of processes running on the system are 265visible as files, and signals may be sent to processes by writing to 266.Pa ctl 267files in the procfs namespace. 268See 269.Xr mount_procfs 8 270for details. 271.It Cd option UDF 272Includes code for the UDF file systems typically found on DVD discs. 273See 274.Xr mount_udf 8 275for details. 276.El 277.Sh FILE SYSTEM OPTIONS 278.Bl -ohang 279.It Cd option BUFCACHEPERCENT= Ns Ar integer 280Percentage of RAM to use as a file system buffer. 281It defaults to 5. 282.It Cd option EXT2FS_SYSTEM_FLAGS 283This option changes the behavior of the APPEND and IMMUTABLE flags 284for a file on an 285.Em EXT2FS 286filesystem. 287Without this option, the superuser or owner of the file can set and clear them. 288With this option, only the superuser can set them, and they can't be cleared 289if the securelevel is greater than 0. 290See also 291.Xr chflags 1 . 292.It Cd option FFS_SOFTUPDATES 293Enables a scheme that uses partial ordering of buffer cache operations 294to allow metadata updates in FFS to happen asynchronously, increasing write 295performance significantly. 296Normally, the FFS filesystem writes metadata updates synchronously which exacts 297a performance penalty in favor of filesystem integrity. 298With soft updates, the performance of asynchronous writes is gained while 299retaining the safety of synchronous metadata updates. 300.Pp 301Soft updates must be enabled on a per-filesystem basis. 302See 303.Xr mount 8 304for details. 305.Pp 306Processors with a small kernel address space, such as the sun4 and sun4c, do 307not have enough kernel memory to support soft updates. 308Attempts to use this option with these CPUs will cause a kernel hang or panic 309after a short period of use as the kernel will quickly run out of memory. 310This is not related to the amount of physical memory present in the machine -- 311it is a limitation of the CPU architecture itself. 312.It Cd option FIFO 313Adds support for 314.At V 315style FIFOs (i.e., 316.Dq named pipes ) . 317This option is recommended in almost all cases as many programs use these. 318.It Cd option NFSSERVER 319Include the server side of the 320.Em NFS 321(Network File System) remote file sharing protocol. 322Although the bulk of the code implementing 323.Em NFS 324is kernel based, several user level daemons are needed for it to 325work. 326See 327.Xr mountd 8 328and 329.Xr nfsd 8 330for details. 331.It Cd option QUOTA 332Enables kernel support for file system quotas. 333See 334.Xr quotaon 8 , 335.Xr edquota 8 , 336.Xr repquota 8 , 337and 338.Xr quota 1 339for details. 340Note that quotas only work on 341.Dq ffs 342file systems, although 343.Xr rpc.rquotad 8 344permits them to be accessed over 345.Em NFS . 346.It Cd option UFS_DIRHASH 347This option enables using an in memory hash table to speed lookups 348in large directories. 349.El 350.Sh MISCELLANEOUS OPTIONS 351.Bl -ohang 352.It Cd option APERTURE 353Provide in-kernel support for controlling VGA framebuffer mapping 354and PCI configuration registers by user-processes 355(such as an X Window System server). 356This option is supported on the 357.Va alpha , 358.Va amd64 , 359.Va i386 , 360.Va macppc , 361and 362.Va sparc64 363architectures. 364.It Cd option BOOT_CONFIG 365Adds support for the 366.Fl c 367boot option (User Kernel Config). 368Allows modification of kernel settings (e.g., device parameters) before 369booting the system. 370.It Cd option CRYPTO 371Enables support for the kernel cryptographic framework. 372See 373.Xr crypto 9 374for details. 375While not IP specific, this option is usually used in conjunction with option 376.Em IPSEC . 377.It Cd option EISAVERBOSE 378Makes the boot process more verbose for EISA peripherals. 379.It Cd option INSECURE 380Hardwires the kernel security level at \-1. 381This means that the system always runs in securelevel 0 mode, even when 382running multiuser. 383See 384.Xr init 8 385for details on the implications of this. 386The kernel secure level may be manipulated by the superuser by altering the 387.Em kern.securelevel 388sysctl variable. 389(It should be noted that the securelevel may only be lowered by a call from 390process ID 1, i.e., 391.Xr init 8 . ) 392See also 393.Xr sysctl 8 394and 395.Xr sysctl 3 . 396.It Cd option KMEMSTATS 397The kernel memory allocator, 398.Xr malloc 9 , 399will keep statistics on its performance if this option is enabled. 400Note that this option is silently turned on by the 401.Cm DEBUG 402option. 403.It Cd option LKM 404Enables support for loadable kernel modules. 405See 406.Xr lkm 4 407for details. 408.Em Note: 409This option is not yet available on all architectures. 410.It Cd option MACOBIOVERBOSE 411Makes the boot process more verbose for OBIO peripherals on the 412.Va macppc 413architecture. 414.It Cd option MULTIPROCESSOR 415On those architectures that have it, this enables multiprocessor support. 416.It Cd option PCIVERBOSE 417Makes the boot process more verbose for PCI peripherals 418(vendor names and other information is printed, etc.). 419.It Cd option PCMCIAVERBOSE 420Makes the boot process more verbose for PCMCIA peripherals. 421.It Cd option USER_LDT 422Enable userland manipulation of per-process 423Local Descriptor Table (LDT) entries; 424see 425.Xr i386_set_ldt 2 426and the 427.Va machdep.userldt 428.Xr sysctl 8 . 429This option is supported on the 430.Va i386 431architecture. 432.It Cd option USER_PCICONF 433Enables the user level access to the PCI bus configuration space 434through ioctls on the 435.Pa /dev/pci 436device. 437It's used by the 438.Xr Xorg 1 439server on some architectures. 440See 441.Xr pci 4 442for details. 443.It Cd option UVM_SWAP_ENCRYPT 444Enables kernel support for encrypting pages that are written out to 445swap storage. 446Swap encryption prevents sensitive data from remaining 447on the disk even after the operating system has been shut down. 448This option should be turned on if cryptographic filesystems are used. 449The sysctl variable 450.Em vm.swapencrypt.enable 451controls its behaviour. 452See 453.Xr sysctl 8 454and 455.Xr sysctl 3 456for details. 457.El 458.Sh NETWORKING OPTIONS 459.Bl -ohang 460.It Cd option ALTQ 461Enables ALTQ (Alternate Queuing). 462See 463.Xr pfctl 8 464and 465.Xr pf.conf 5 466to set up the interface transmission rate and queueing disciplines. 467.Em ALTQ_CBQ , 468.Em ALTQ_RED , 469.Em ALTQ_PRIQ 470and 471.Em ALTQ_HFSC 472are enabled by default with option 473.Em ALTQ 474in 475.Ox . 476See 477.Xr altq 9 478for details on ALTQ. 479.It Cd option ENCDEBUG 480This option enables debugging information to be conditionally logged 481in case IPSEC encounters errors. 482The option 483.Em IPSEC 484is required along with this option. 485Debug logging can be turned on/off through the use of the 486.Em net.inet.ip.encdebug 487sysctl variable. 488If 489.Em net.inet.ip.encdebug 490is 1, debug logging is on. 491See 492.Xr sysctl 8 493and 494.Xr sysctl 3 495for details. 496.It Cd option INET 497Includes support for the TCP/IP protocol stack. 498This option is currently required. 499See 500.Xr inet 4 501for details. 502.It Cd option INET6 503Includes support for the IPv6 protocol stack. 504See 505.Xr inet6 4 506for details. 507Unlike 508.Em INET , 509.Em INET6 510enables multicast routing code as well. 511This option requires 512.Em INET 513at this moment, but it should not. 514.It Cd option IPSEC 515This option enables IP security protocol support. 516See 517.Xr ipsec 4 518for more details. 519.It Cd option KEY 520Enables PFKEYv2 (RFC 2367) support. 521While not IP specific, this option is usually used in conjunction with option 522.Em IPSEC . 523.It Cd option MROUTING 524Includes support for IP multicast routers. 525.Em INET 526should be set along with this. 527Multicast routing is controlled by the 528.Xr mrouted 8 529daemon. 530.It Cd option ND6_DEBUG 531The option sets the default value of 532.Em net.inet6.icmp6.nd6_debug 533to 1, 534for debugging IPv6 neighbor discovery protocol handling. 535See 536.Xr sysctl 3 537for details. 538.It Cd option PIPEX 539Includes pipex in-kernel acceleration for PPPoE, L2TP or PPTP. 540See 541.Xr pipex 4 542for details. 543.It Cd option PPP_BSDCOMP 544Enables BSD compressor for PPP connections. 545.It Cd option PPP_DEFLATE 546For use in conjunction with PPP_BSDCOMP; provides an interface to zlib for PPP 547for deflate compression/decompression. 548.It Cd option SOCKET_SPLICE 549Enables zero-copy socket splicing in the kernel. 550See 551.Dv SO_SPLICE 552in 553.Xr setsockopt 2 554and 555.Xr sosplice 9 556for details. 557.It Cd option TCP_ECN 558Turns on Explicit Congestion Notification (RFC 3168). 559.Em ECN 560allows intermediate routers to use the Congestion Experienced 561codepoint in the IP header as an indication of congestion, and allows 562TCP to adjust the transmission rate using this signal. 563Both communication endpoints negotiate enabling 564.Em ECN 565functionality at the TCP connection establishment. 566.It Cd option TCP_FACK 567Turns on forward acknowledgements allowing a more precise estimate of 568outstanding data during the fast recovery phase by using 569.Em SACK 570information. 571This option can only be used together with 572.Em TCP_SACK . 573.It Cd option TCP_SACK 574Turns on selective acknowledgements. 575Additional information about 576segments already received can be transmitted back to the sender, 577thus indicating segments that have been lost and allowing for 578a swifter recovery. 579Both communication endpoints need to support 580.Em SACK . 581The fallback behaviour is NewReno fast recovery phase, which allows 582one lost segment to be recovered per round trip time. 583When more than one segment has been dropped per window, the transmission can 584continue without waiting for a retransmission timeout. 585.It Cd option TCP_SIGNATURE 586Turns on support for the TCP MD5 Signature option (RFC 2385). 587This is used by 588Internet backbone routers to provide per-packet authentication for the TCP 589packets used to communicate BGP routing information. 590You will also need a 591routing daemon that supports this option in order to actually use it. 592.El 593.Sh OPERATION RELATED OPTIONS 594.Bl -ohang -compact 595.It Cd option BUFPAGES= Ns Ar value 596.It Cd option NBUF= Ns Ar value 597These options set the number of pages available for the buffer cache. 598Their default value is a machine dependent value, often calculated as 599between 5% and 10% of total available RAM. 600.Pp 601.It Cd option DST= Ns Ar value 602If 603.Ar value 604is non-zero, indicates that the hardware realtime clock device 605is one hour ahead of the offset given in 606.Sq TIMEZONE , 607due to Daylight Saving Time (DST). 608If 609.Ar value 610is zero, the hardware realtime clock device is not in Daylight Saving Time. 611.Pp 612.It Cd option NKMEMPAGES= Ns Ar value 613.It Cd option NKMEMPAGES_MAX= Ns Ar value 614Size of kernel malloc area in PAGE_SIZE-sized logical pages. 615This area is covered by the kernel submap 616.Em kmem_map . 617The kernel attempts to auto-size this map based on the amount of 618physical memory in the system. 619Platform-specific code may place bounds on this computed size, 620which may be viewed with the 621.Xr sysctl 8 622variable 623.Em vm.nkmempages . 624See 625.Pa /usr/include/machine/param.h 626for the default upper bound. 627The related option 628.Sq NKMEMPAGES_MAX 629allows the bounds to be overridden in the kernel configuration file 630in the event the computed value is insufficient resulting in an 631.Dq out of space in kmem_map 632panic. 633.Pp 634.It Cd option \&"TIMEZONE= Ns Ar value Ns Cm \&" 635.Ar value 636indicates the time zone offset of the hardware realtime clock device, 637in minutes, 638from UTC. 639It is useful when the hardware realtime clock device is configured 640with local time, 641when dual-booting 642.Ox 643with other operating systems on a single machine. 644For instance, if the hardware realtime clock is set to Tokyo time, 645.Ar value 646should be 647.Li \&-540 648as Tokyo local time is 9 hours ahead of UTC. 649Double quotes are needed when specifying a negative 650.Ar value . 651.El 652.Sh SCSI SUBSYSTEM OPTIONS 653.Bl -ohang 654.It Cd option SCSI_DELAY= Ns Ar value 655Delay for 656.Ar value 657seconds before starting to probe the first SCSI bus. 658This can be used if a SCSI device needs extra time to get ready. 659.It Cd option SCSIDEBUG 660Enable printing of SCSI subsystem debugging info to the console. 661Each of 662.Em SCSIDEBUG_LEVEL , 663.Em SCSIDEBUG_BUSES , 664.Em SCSIDEBUG_TARGETS 665and 666.Em SCSIDEBUG_LUNS 667must have non-zero values for any debugging info to be printed. 668Only 669.Em SCSIDEBUG_LEVEL 670has a default value (SDEV_DB1 | SDEV_DB2) that is non-zero. 671.It Cd option SCSIDEBUG_BUSES= Ns Ar value 672Define which SCSI buses will print debug info. 673Each bit enables debugging info for the corresponding bus. 674e.g. a value of 0x1 enables debug info for bus 0. 675.It Cd option SCSIDEBUG_LEVEL= Ns Ar value 676Define which of the four levels of debugging info are printed. 677Each bit enables a level, and multiple levels are specified by setting multiple 678bits. 679.Bd -literal -offset indent 6800x0010 (SDEV_DB1) SCSI commands, errors, and data 6810x0020 (SDEV_DB2) routine flow 6820x0040 (SDEV_DB3) routine internals 6830x0080 (SDEV_DB4) miscellaneous addition debugging 684.Ed 685.Pp 686If 687.Em SCSIDEBUG_LEVEL 688is undefined, a value of 0x0030 (SDEV_DB1|SDEV_DB2) is used. 689.It Cd option SCSIDEBUG_LUNS= Ns Ar value 690Define which SCSI luns will print debug info. 691Each bit enables debugging info for the corresponding lun. 692.It Cd option SCSIDEBUG_TARGETS= Ns Ar value 693Define which SCSI targets will print debug info. 694Each bit enables debugging info for the corresponding target. 695.It Cd option SCSITERSE 696Terser SCSI error messages. 697This omits the table for decoding ASC/ASCQ info, saving about 30KB. 698.El 699.Sh SYSTEM V IPC OPTIONS 700.Bl -ohang 701.It Cd option SEMMNI= Ns Ar value 702Number of semaphore identifiers (also called semaphore handles 703and semaphore sets) available in the system. 704Default value is 10. 705The kernel allocates memory for the control structures at startup, 706so arbitrarily large values should be avoided. 707.It Cd option SEMMNS= Ns Ar value 708Maximum number of semaphores in all sets in the system. 709Default value is 60. 710.It Cd option SEMMNU= Ns Ar value 711Maximum number of semaphore undo structures in the system. 712Default value is 30. 713.It Cd option SEMUME= Ns Ar value 714Maximum number of per-process undo operation entries in the 715system. 716Semaphore undo operations are invoked by the kernel when 717.Xr semop 2 718is called with the SEM_UNDO flag and the process holding 719the semaphores terminates unexpectedly. 720Default value is 10. 721.It Cd option SHMMAXPGS= Ns Ar value 722Sets the maximum number of 723.At V 724style shared memory pages that are available through the 725.Xr shmget 2 726system call. 727Default value is 1024 on most architectures. 728See 729.Pa /usr/include/machine/vmparam.h 730for the default. 731.It Cd option SYSVMSG 732Includes support for 733.At V 734style message queues. 735See 736.Xr msgctl 2 , 737.Xr msgget 2 , 738.Xr msgrcv 2 , 739.Xr msgsnd 2 . 740.It Cd option SYSVSEM 741Includes support for 742.At V 743style semaphores. 744See 745.Xr semctl 2 , 746.Xr semget 2 , 747.Xr semop 2 . 748.It Cd option SYSVSHM 749Includes support for 750.At V 751style shared memory. 752See 753.Xr shmat 2 , 754.Xr shmctl 2 , 755.Xr shmdt 2 , 756.Xr shmget 2 . 757.El 758.Sh SEE ALSO 759.Xr intro 4 , 760.Xr files.conf 5 , 761.Xr config 8 , 762.Xr sysctl 8 763.Sh HISTORY 764The 765.Nm 766man page first appeared in 767.Ox 2.3 . 768.Sh BUGS 769The 770.Em INET 771option should not be required. 772