1.\" $NetBSD: options.4,v 1.509 2020/03/07 23:17:47 tnn Exp $ 2.\" 3.\" Copyright (c) 1996 4.\" Perry E. Metzger. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgment: 16.\" This product includes software developed for the NetBSD Project 17.\" by Perry E. Metzger. 18.\" 4. The name of the author may not be used to endorse or promote products 19.\" derived from this software without specific prior written permission. 20.\" 21.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 22.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 23.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 24.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 25.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 26.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 27.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 28.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 29.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 30.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 31.\" 32.\" 33.Dd March 7, 2020 34.Dt OPTIONS 4 35.Os 36.Sh NAME 37.Nm options 38.Nd Miscellaneous kernel configuration options 39.Sh SYNOPSIS 40.Cd cinclude ... 41.Cd config ... 42.Cd [no] file-system ... 43.Cd ident ... 44.Cd include ... 45.Cd [no] makeoptions ... 46.Cd maxusers ... 47.Cd [no] options ... 48.Cd [no] pseudo-device ... 49.Sh DESCRIPTION 50This manual page describes a number of miscellaneous kernel 51configuration options that may be specified in a kernel config 52file. 53See 54.Xr config 1 55and 56.Xr config 5 57for information on how to configure and build kernels. 58.Pp 59The 60.Ar no 61form removes a previously specified option. 62.Ss Keywords 63The following keywords are recognized in a kernel configuration file: 64.Bl -ohang 65.It Sy cinclude Qq Ar filename 66Conditionally includes another kernel configuration file whose name is 67.Ar filename , 68which may be double-quoted and may be an explicit path or relative to 69the kernel source directory. 70Failure to open the named file is ignored. 71.It Sy config Ar exec_name No root on Ar rootdev Oo type Ar fstype Oc \ 72Oo dumps on Ar dumpdev Oc 73Defines a configuration whose kernel executable is named 74.Ar exec_name , 75normally 76.Dq netbsd , 77with its root file system of type 78.Ar fstype 79on the device 80.Ar rootdev , 81and optionally specifying the location of kernel core dumps on the device 82.Ar dumpdev . 83.Ar dev 84or 85.Ar dumpdev 86and 87.Ar fstype 88may be specified as 89.Dq \&? , 90which is a wild card. 91The root 92.Ar fstype 93and 94.Ar dumpdev 95are optional and assumed to be wild carded if they are not specified. 96.It Ar device_instance No at Ar attachment \ 97Oo Ar locators value Oo ... Oc Oc Oo flags Ar value Oc 98Define an instance of the device driver 99.Ar device_instance 100that attaches to the bus or device named 101.Ar attachment . 102An 103.Ar attachment 104may require additional information on where the device can be found, such 105as an address, channel, function, offset, and/or slot, referred to as 106.Ar locators , 107whose 108.Ar value 109often may be a wild card, 110.Dq \&? . 111Some device drivers have one or more 112.Ar flags 113that can be adjusted to affect the way they operate. 114.It Sy file-system Ar fs_name Op , Ar fs_name Op ... 115Include support for the file-system 116.Ar fs_name . 117.It Sy ident Qq Ar string 118Sets the kernel identification string to 119.Ar string . 120.It Sy include Qq Ar filename 121Functions the same as 122.Ar cinclude , 123except failure to open 124.Ar filename 125produces a fatal error. 126.It Sy makeoptions Ar name=value 127Defines a 128.Xr make 1 129macro 130.Ar name 131with the value 132.Ar value 133in the kernel Makefile. 134.It Sy maxusers Ar integer 135Set the maxusers variable in the kernel. 136.It Sy no Ar keyword Ar name Op Ar arguments Op ... 137For the 138.Xr config 1 139.Ar keywords 140file-system, makeoptions, options, and pseudo-device, 141.Ar no 142removes the file-system, makeoption, options, or pseudo-device, 143.Ar name . 144This is useful when a kernel configuration file includes another which 145has undesired options. 146.Pp 147For example, a local configuration file that wanted the kitchen sink, but 148not COMPAT_09 or bridging, might be: 149.Bd -literal -offset indent 150include "arch/i386/conf/GENERIC" 151no options COMPAT_09 152no pseudo-device bridge 153.Ed 154.It Sy options Ar option_name Op , Ar option_name=value Op ... 155Specifies (or sets) the option, or comma-separated list of options, 156.Ar option_name . 157Some options expect to be assigned a value, which may be an integer, 158a double-quoted word, a bare word, or an empty string 159.Pq Qq . 160Note that those are eventually handled by the C compiler, so the rules 161of that language apply. 162.Pp 163.Em Note : 164Options that are not defined by device definition files are passed to 165the compile process as 166.Fl D 167flags to the C compiler. 168.It Sy pseudo-device Ar name Op Ar N 169Includes support for the pseudo-device 170.Ar name . 171Some pseudo-devices can have multiple or 172.Ar N 173instances. 174.El 175.Ss Compatibility Options 176Note that compatibility options for older 177.Nx 178releases includes support for newer releases as well. 179This means that typically only one of these is necessary, with the 180.Cd COMPAT_09 181option enabling all 182.Nx 183compatibility. 184This does not include the 185.Cd COMPAT_43 186or 187.Cd COMPAT_44 188options. 189.Bl -ohang 190.It Cd options COMPAT_09 191Enable binary compatibility with 192.Nx 0.9 . 193This enables support for 19416-bit user, group, and process IDs (following revisions support 19532-bit identifiers). 196It also allows the use of the deprecated 197.Xr getdomainname 3 , 198.Xr setdomainname 3 , 199and 200.Xr uname 3 201syscalls. 202This option also allows using numeric file system identifiers rather 203than strings. 204Post 205.Nx 0.9 206versions use string identifiers. 207.It Cd options COMPAT_10 208Enable binary compatibility with 209.Nx 1.0 . 210This option allows the use of the file system name of 211.Dq ufs 212as an alias for 213.Dq ffs . 214The name 215.Dq ffs 216should be used post 1.0 in 217.Pa /etc/fstab 218and other files. 219It also adds old syscalls for the 220.At V 221shared memory interface. 222This was changed post 1.0 to work on 64-bit architectures. 223This option also enables 224.Dq sgtty 225compatibility, without which programs using the old interface produce 226an 227.Dq inappropriate ioctl 228error, and 229.Pa /dev/io 230only works when this option is set in the kernel, 231see 232.Xr io 4 233on ports that support it. 234.It Cd options COMPAT_11 235Enable binary compatibility with 236.Nx 1.1 . 237This allows binaries running on the i386 port to gain direct access to 238the io ports by opening 239.Pa /dev/io 240read/write. 241This functionality was replaced by 242.Xr i386_iopl 2 243post 1.1. 244On the Atari port, the location of the disk label was moved after 1.1. 245When the 246.Em COMPAT_11 247option is set, the kernel will read (pre) 1.1 style disk labels as a 248last resort. 249When a disk label is re-written, the old style label will be replaced 250with a post 1.1 style label. 251This also enables the 252.Em EXEC_ELF_NOTELESS 253option. 254.It Cd options COMPAT_12 255Enable binary compatibility with 256.Nx 1.2 . 257This allows the use of old syscalls for 258.Fn reboot 259and 260.Fn swapon . 261The syscall numbers were changed post 1.2 to add functionality to the 262.Xr reboot 2 263syscall, and the new 264.Xr swapctl 2 265interface was introduced. 266This also enables the 267.Em EXEC_ELF_NOTELESS 268option. 269.It Cd options COMPAT_13 270Enable binary compatibility with 271.Nx 1.3 . 272This allows the use of old syscalls for 273.Fn sigaltstack , 274and also enables the old 275.Xr swapctl 2 276command 277.Dv SWAP_STATS 278(now called 279.Dv SWAP_OSTATS ) , 280which does not include the 281.Fa se_path 282member of 283.Va struct swapent . 284.It Cd options COMPAT_14 285Enable binary compatibility with 286.Nx 1.4 . 287This allows some old 288.Xr ioctl 2 289on 290.Xr wscons 4 291to be performed, and allows the 292.Dv NFSSVC_BIOD 293mode of the 294.Xr nfssvc 2 295system call to be used for compatibility with the deprecated nfsiod program. 296.It Cd options COMPAT_15 297Enable binary compatibility with 298.Nx 1.5 . 299Since there were no API changes from 300.Nx 1.5 301and 302.Nx 1.6 , 303this option does nothing. 304.It Cd options COMPAT_16 305Enable binary compatibility with 306.Nx 1.6 . 307This allows the use of old signal trampoline code which has been deprecated 308with the addition of 309.Xr siginfo 2 . 310.It Cd options COMPAT_20 311Enable binary compatibility with 312.Nx 2.0 . 313This allows the use of old syscalls for 314.Fn statfs , 315.Fn fstatfs , 316.Fn getfsstat 317and 318.Fn fhstatfs , 319which have been deprecated with the addition of the 320.Xr statvfs 2 , 321.Xr fstatvfs 2 , 322.Xr getvfsstat 2 323and 324.Xr fhstatvfs 2 325system calls. 326.It Cd options COMPAT_30 327Enable binary compatibility with 328.Nx 3.0 . 329See 330.Xr compat_30 8 331for details about the changes made after the 332.Nx 3.0 333release. 334.It Cd options COMPAT_40 335Enable binary compatibility with 336.Nx 4.0 . 337This allows the use of old 338.Xr ptrace 2 339calls for the SH3 platform. 340It also enables the old 341.Xr mount 2 342system call that did not include the data length parameter. 343The power_event_t structure's pev_switch is filled in. 344.It Cd options COMPAT_43 345Enables compatibility with 346.Bx 4.3 . 347This adds an old syscall for 348.Xr lseek 2 . 349It also adds the ioctls for 350.Dv TIOCGETP 351and 352.Dv TIOCSETP . 353The return values for 354.Xr getpid 2 , 355.Xr getgid 2 , 356and 357.Xr getuid 2 358syscalls are modified as well, to return the parent's PID and 359UID as well as the current process's. 360It also enables the deprecated 361.Dv NTTYDISC 362terminal line discipline. 363It also provides backwards compatibility with 364.Dq old 365SIOC[GS]IF{ADDR,DSTADDR,BRDADDR,NETMASK} interface ioctls, including 366binary compatibility with code written before the introduction of the 367sa_len field in sockaddrs. 368It also enables 369support for some older pre 370.Bx 4.4 371socket calls. 372.It Cd options COMPAT_50 373Enable binary compatibility with 374.Nx 5.0 . 375This enables support for the old 376.Ft time_t 377and 378.Ft dev_t 379types as 32 bit, and all the associated kernel interface changes. 380It also enables old 381.Xr gpio 4 382and 383.Xr rnd 4 384interfaces. 385.It Cd options COMPAT_60 386Enable binary compatibility with 387.Nx 6.0 . 388This provides old 389.Xr ccd 4 390interfaces, enables support for old 391.Xr cpuctl 8 392microcode interfaces, and support for the old 393.Ft ptmget 394structure. 395.It Cd options COMPAT_70 396Enable binary compatibility with 397.Nx 7.0 . 398This provides support for old 399.Xr route 4 400interfaces. 401.It Cd options COMPAT_BSDPTY 402This option is currently on by default and enables the pty multiplexer 403.Xr ptm 4 404and 405.Xr ptmx 4 406to find and use ptys named 407.Pa /dev/ptyXX 408(master) and 409.Pa /dev/ttyXX 410(slave). 411Eventually this option will become optional as ptyfs based pseudo-ttys become 412the default, see 413.Xr mount_ptyfs 8 . 414.It Cd options COMPAT_LINUX 415On those architectures that support it, this enables binary 416compatibility with Linux ELF and 417.Xr a.out 5 418applications built for the same architecture. 419This currently includes the alpha, arm, i386, m68k, mips, powerpc and 420x86_64 ports. 421.It Cd options COMPAT_LINUX32 422On those 64 bit architectures that support it, this enables binary 423compatibility with 32 bit Linux binaries. 424For now this is limited to running i386 ELF Linux binaries on amd64. 425.It Cd options COMPAT_SUNOS 426On those architectures that support it, this enables binary 427compatibility with SunOS 4.1 applications built for the same architecture. 428This currently includes the sparc, sparc64 and most or all m68k ports. 429Note that the sparc64 requires the 430.Em COMPAT_NETBSD32 431option for 64-bit kernels, in addition to this option. 432.It Cd options COMPAT_ULTRIX 433On those architectures that support it, this enables binary 434compatibility with ULTRIX applications built for the same architecture. 435This currently is limited to the pmax. 436The functionality of this option is unknown. 437.It Cd options COMPAT_FREEBSD 438On those architectures that support it, this enables binary 439compatibility with 440.Fx 441applications built for the same architecture. 442At the moment this is limited to the i386 port. 443.It Cd options COMPAT_NOMID 444Enable compatibility with 445.Xr a.out 5 446executables that lack a machine ID. 447This includes 448.Nx 0.8 Ns 's 449ZMAGIC format, and 386BSD and BSDI's 450QMAGIC, NMAGIC, and OMAGIC 451.Xr a.out 5 452formats. 453.It Cd options COMPAT_NETBSD32 454On those architectures that support it, this enables binary 455compatibility with 32-bit applications built for the same architecture. 456This is currently limited to the amd64 and sparc64 ports, and only 457applicable for 64-bit kernels. 458.It Cd options COMPAT_AOUT_M68K 459On m68k architectures which have switched to ELF, 460this enables binary compatibility with 461.Nx Ns /m68k 462.Xr a.out 5 463executables on 464.Nx Ns /m68k 465ELF kernels. 466This handles alignment incompatibility of m68k ABI between 467a.out and ELF which causes the structure padding differences. 468Currently only some system calls which use 469.Va struct stat 470are adjusted and some binaries which use 471.Xr sysctl 3 472to retrieve network details would not work properly. 473.It Cd options EMUL_NATIVEROOT=string 474Just like emulated binaries first try looking up files in 475an emulation root (e.g. 476.Pa /emul/linux ) 477before looking them up in real root, this option causes native 478binaries to first look up files in an "emulation" directory too. 479This can be useful to test an amd64 kernel on top of an i386 system 480before full migration: by unpacking the amd64 distribution in e.g. 481.Pa /emul/netbsd64 482and specifying that location as 483.Cd EMUL_NATIVEROOT , 484native amd64 binaries can be run while the root file system remains 485populated with i386 binaries. 486Beware of 487.Pa /dev 488incompatibilities between i386 and amd64 if you do this. 489.It Cd options EXEC_ELF_NOTELESS 490Run unidentified ELF binaries as 491.Nx 492binaries. 493This might be needed for very old 494.Nx 495ELF binaries on some archs. 496These old binaries didn't contain an appropriate 497.Li .note.netbsd.ident 498section, and thus can't be identified by the kernel as 499.Nx 500binaries otherwise. 501Beware - if this option is on, the kernel would run 502.Em any 503unknown ELF binaries as if they were 504.Nx 505binaries. 506.El 507.Ss Debugging Options 508.Bl -ohang 509.It Cd options DDB 510Compiles in a kernel debugger for diagnosing kernel problems. 511See 512.Xr ddb 4 513for details. 514.Em NOTE : 515not available on all architectures. 516.It Cd options DDB_FROMCONSOLE=integer 517If set to non-zero, DDB may be entered by sending a break on a serial 518console or by a special key sequence on a graphics console. 519A value of "0" ignores console breaks or key sequences. 520If not explicitly specified, the default value is "1". 521Note that this sets the value of the 522.Em ddb.fromconsole 523.Xr sysctl 3 524variable which may be changed at run time \(em see 525.Xr sysctl 8 526for details. 527.It Cd options DDB_HISTORY_SIZE=integer 528If this is non-zero, enable history editing in the kernel debugger 529and set the size of the history to this value. 530.It Cd options DDB_ONPANIC 531The default if not specified is 532.Dq 1 533- just enter into DDB. 534If set to 535.Dq 0 536the kernel will attempt to print out a stack trace 537and reboot the system. 538If set to 539.Dq -1 540then neither a stack trace is printed or DDB entered - 541it is as if DDB were not compiled into the kernel. 542Note that this sets the value of the 543.Em ddb.onpanic 544.Xr sysctl 3 545variable which may be changed at run time \(em see 546.Xr sysctl 8 547for details. 548.It Cd options DDB_COMMANDONENTER=string 549This option specify commands which will be executed on each entry to DDB. 550This sets the default value of the 551.Em ddb.commandonenter 552.Xr sysctl 3 553variable which may be changed at run time. 554.It Cd options DDB_BREAK_CHAR=integer 555This option overrides using break to enter the kernel debugger 556on the serial console. 557The value given is the ASCII value to be used instead. 558This is currently only supported by the com driver. 559.It Cd options DDB_VERBOSE_HELP 560This option adds more verbose descriptions to the 561.Em help 562command. 563.It Cd options DDB_PANICSTACKFRAMES=integer 564Number of stack frames to display on panic. 565Useful to avoid scrolling away the interesting frames on a glass tty. 566Default value is 567.Dv 65535 568(all frames), useful value around 569.Dv 10 . 570.It Cd options KGDB 571Compiles in a remote kernel debugger stub for diagnosing kernel problems 572using the 573.Dq remote target 574feature of gdb. 575See 576.Xr gdb 1 577for details. 578.Em NOTE : 579not available on all architectures. 580.It Cd options KGDB_DEV 581Device number 582.Po 583as a 584.Dv dev_t 585.Pc 586of kgdb device. 587.It Cd options KGDB_DEVADDR 588Memory address of kgdb device. 589.It Cd options KGDB_DEVMODE 590Permissions of kgdb device. 591.It Cd options KGDB_DEVNAME 592Device name of kgdb device. 593.It Cd options KGDB_DEVRATE 594Baud rate of kgdb device. 595.It Cd makeoptions DEBUG="-g" 596The 597.Fl g 598flag causes 599.Pa netbsd.gdb 600to be built in addition to 601.Pa netbsd . 602.Pa netbsd.gdb 603is useful for debugging kernel crash dumps with gdb. 604See 605.Xr gdb 1 606for details. 607.It Cd options DEBUG 608Turns on miscellaneous kernel debugging. 609Since options are turned into preprocessor defines (see above), 610.Em options DEBUG 611is equivalent to doing a 612.Em #define DEBUG 613throughout the kernel. 614Much of the kernel has 615.Em #ifdef DEBUG 616conditionalized debugging code. 617Note that many parts of the kernel (typically device drivers) include their own 618.Em #ifdef XXX_DEBUG 619conditionals instead. 620This option also turns on certain other options, 621which may decrease system performance. 622Systems with this option are not suitable for regular use, and are 623intended only for debugging or looking for bugs. 624.It Cd options DIAGNOSTIC 625Adds code to the kernel that does internal consistency checks. 626This code will cause the kernel to panic if corruption of internal data 627structures is detected. 628Historically, the performance degradation is sufficiently small that 629it is reasonable for systems with 630.Em options DIAGNOSTIC 631to be in production use, with the real consideration not being 632performance but instead a preference for more panics versus continued 633operation with undetected problems. 634.It Cd options LOCKDEBUG 635Adds code to the kernel to detect incorrect use of locking primitives 636(mutex, rwlock). 637This code will cause the kernel to check for dead lock conditions. 638It will also check for memory being freed to not contain initialised 639lock primitives. 640Functions for use in 641.Xr ddb 4 642to check lock chains etc. are also enabled. 643These checks are very expensive and can decrease performance on 644multi-processor machines by a factor of three. 645.It Cd options KDTRACE_HOOKS 646Adds hooks for the DTrace tracing facility, which allows users to 647analyze many aspects of system and application behavior. 648See 649.Xr dtrace 1 650for details. 651.It Cd options KSTACK_CHECK_MAGIC 652Check kernel stack usage and panic if stack overflow is detected. 653This check is performance sensitive because it scans stack on each context 654switch. 655.It Cd options KTRACE 656Add hooks for the system call tracing facility, which allows users to 657watch the system call invocation behavior of processes. 658See 659.Xr ktrace 1 660for details. 661.It Cd options MSGBUFSIZE=integer 662This option sets the size of the kernel message buffer. 663This buffer holds the kernel output of 664.Fn printf 665when not (yet) read by 666.Xr syslogd 8 . 667This is particularly useful when the system has crashed and you wish to lookup 668the kernel output from just before the crash. 669Also, since the autoconfig output becomes more and more verbose, 670it sometimes happens that the message buffer overflows before 671.Xr syslogd 8 672was able to read it. 673Note that not all systems are capable of obtaining a variable sized message 674buffer. 675There are also some systems on which memory contents are not preserved 676across reboots. 677.It Cd options KERNHIST 678Enables the kernel history logs, which create in-memory traces of 679various kernel activities. 680These logs can be displayed by using 681.Cm show kernhist 682from DDB. 683See the kernel source file 684.Pa sys/kern/kern_history.c 685and the 686.Xr kernhist 9 687manual for details. 688.It Cd options KERNHIST_PRINT 689Prints the kernel history logs on the system console as entries are added. 690Note that the output is 691.Em extremely 692voluminous, so this option is really only useful for debugging 693the very earliest parts of kernel initialization. 694.It Cd options UVMHIST 695Like 696.Em KERNHIST , 697it enables the UVM history logs. 698These logs can be displayed by using 699.Cm show kernhist 700from DDB. 701See the kernel source file 702.Pa sys/uvm/uvm_stat.c 703for details. 704.It Cd options UVMHIST_PRINT 705Like 706.Em UVMHIST , 707it prints the UVM history logs on the system console as entries are added. 708Note that the output is 709.Em extremely 710voluminous, so this option is really only useful for debugging 711the very earliest parts of kernel initialization. 712.It Cd options UVMHIST_MAPHIST_SIZE 713Set the size of the 714.Dq maphist 715kernel history. 716The default is 100. 717This option depends upon the 718.Em UVMHIST 719option. 720.It Cd options UVMHIST_PDHIST_SIZE 721Set the size of the 722.Dq pdhist 723kernel history. 724The default is 100. 725This option depends upon the 726.Em UVMHIST 727option. 728.It Cd options BIOHIST 729Like 730.Em KERNHIST , 731it enables the BIO history logs. 732These logs can be displayed by using 733.Cm show kernhist 734from DDB, and can help in debugging problems with Buffered I/O operations. 735See the kernel source file 736.Pa sys/kern/vfs_vio.c 737for details. 738.It Cd options BIOHIST_PRINT 739Like 740.Em BIOHIST , 741it prints the BIO history logs on the system console as entries are added. 742Note that the output is 743.Em extremely 744voluminous, so this option is really only useful for debugging 745the very earliest parts of kernel initialization. 746.It Cd options BIOHIST_SIZE 747Set the size of the 748.Dq biohist 749kernel history. 750The default is 500. 751This option depends upon the 752.Em BIOHIST 753option. 754.El 755.Ss File Systems 756.Bl -ohang 757.It Cd file-system FFS 758Includes code implementing the Berkeley Fast File System 759.Po Em FFS Pc . 760Most machines need this if they are not running diskless. 761.It Cd file-system EXT2FS 762Includes code implementing the Second Extended File System 763.Po Em ext2 Pc , 764revision 0 and revision 1 with the 765.Em filetype , 766.Em sparse_super 767and 768.Em large_file 769options. 770This is the most commonly used file system on the Linux operating system, 771and is provided here for compatibility. 772Some of the specific features of 773.Em ext2 774like the "behavior on errors" are not implemented. 775See 776.Xr mount_ext2fs 8 777for details. 778.It Cd file-system LFS 779.Bq Em EXPERIMENTAL 780Include the Log-structured File System 781.Po Em LFS Pc . 782See 783.Xr mount_lfs 8 784and 785.Xr newfs_lfs 8 786for details. 787.It Cd file-system MFS 788Include the Memory File System 789.Po Em MFS Pc . 790This file system stores files in swappable memory, and produces 791notable performance improvements when it is used as the file store 792for 793.Pa /tmp 794and similar file systems. 795See 796.Xr mount_mfs 8 797for details. 798.It Cd file-system NFS 799Include the client side of the Network File System (NFS) 800remote file sharing protocol. 801Although the bulk of the code implementing NFS 802is kernel based, several user level daemons are needed for it to work. 803See 804.Xr mount_nfs 8 805for details. 806.It Cd file-system CD9660 807Includes code for the ISO 9660 + Rock Ridge file system, which is 808the standard file system on many CD-ROM discs. 809Useful primarily if you have a CD-ROM drive. 810See 811.Xr mount_cd9660 8 812for details. 813.It Cd file-system MSDOSFS 814Includes the MS-DOS FAT file system, which is reportedly still used 815by unfortunate people who have not heard about 816.Nx . 817Also implements the Windows 95 extensions to the same, which permit 818the use of longer, mixed case file names. 819See 820.Xr mount_msdos 8 821and 822.Xr fsck_msdos 8 823for details. 824.It Cd file-system NTFS 825.Bq Em EXPERIMENTAL 826Includes code for the Microsoft Windows NT file system. 827See 828.Xr mount_ntfs 8 829for details. 830.It Cd file-system FDESC 831Includes code for a file system, conventionally mounted on 832.Pa /dev/fd , 833which permits access to the per-process file descriptor space via 834special files in the file system. 835See 836.Xr mount_fdesc 8 837for details. 838Note that this facility is redundant, and thus unneeded on most 839.Nx 840systems, since the 841.Xr fd 4 842pseudo-device driver already provides identical functionality. 843On most 844.Nx 845systems, instances of 846.Xr fd 4 847are mknoded under 848.Pa /dev/fd/ 849and on 850.Pa /dev/stdin , 851.Pa /dev/stdout , 852and 853.Pa /dev/stderr . 854.It Cd file-system KERNFS 855Includes code which permits the mounting of a special file system 856(normally mounted on 857.Pa /kern ) 858in which files representing various kernel variables and parameters 859may be found. 860See 861.Xr mount_kernfs 8 862for details. 863.It Cd file-system NULLFS 864Includes code for a loopback file system. 865This permits portions of the file hierarchy to be re-mounted in other places. 866The code really exists to provide an example of a stackable file system layer. 867See 868.Xr mount_null 8 869for details. 870.It Cd file-system OVERLAY 871Includes code for a file system filter. 872This permits the overlay file system to intercept all access to an underlying 873file system. 874This file system is intended to serve as an example of a stacking file 875system which has a need to interpose itself between an underlying file 876system and all other access. 877See 878.Xr mount_overlay 8 879for details. 880.It Cd file-system PROCFS 881Includes code for a special file system (conventionally mounted on 882.Pa /proc ) 883in which the process space becomes visible in the file system. 884Among 885other things, the memory spaces of processes running on the system are 886visible as files, and signals may be sent to processes by writing to 887.Pa ctl 888files in the procfs namespace. 889See 890.Xr mount_procfs 8 891for details. 892.It Cd file-system UDF 893.Bq Em EXPERIMENTAL 894Includes code for the UDF file system commonly found on CD and DVD 895media but also on USB sticks. 896Currently supports read and write access upto UDF 2.01 and somewhat limited 897write support for UDF 2.50. 898It is marked experimental since there is no 899.Xr fsck_udf 8 . 900See 901.Xr mount_udf 8 902for details. 903.It Cd file-system UMAPFS 904Includes a loopback file system in which user and group IDs may be 905remapped \(em this can be useful when mounting alien file systems with 906different UIDs and GIDs than the local system. 907See 908.Xr mount_umap 8 909for details. 910.It Cd file-system UNION 911.Bq Em EXPERIMENTAL 912Includes code for the union file system, which permits directories to 913be mounted on top of each other in such a way that both file systems 914remain visible \(em this permits tricks like allowing writing (and the 915deleting of files) on a read-only file system like a CD-ROM by 916mounting a local writable file system on top of the read-only file 917system. 918See 919.Xr mount_union 8 920for details. 921.It Cd file-system CODA 922.Bq Em EXPERIMENTAL 923Includes code for the Coda file system. 924Coda is a distributed file system like NFS and AFS. 925It is freely available, like NFS, but it functions much like AFS in being a 926.Dq stateful 927file system. 928Both Coda and AFS cache files on your local machine to improve performance. 929Then Coda goes a step further than AFS by letting you access the cached 930files when there is no available network, viz. disconnected laptops and 931network outages. 932In Coda, both the client and server are outside the kernel which makes 933them easier to experiment with. 934Coda is available for several UNIX and non-UNIX platforms. 935See 936.Lk http://www.coda.cs.cmu.edu 937for more details. 938.Em NOTE : 939You also need to enable the pseudo-device, vcoda, for the Coda 940file system to work. 941.It Cd file-system SMBFS 942.Bq Em EXPERIMENTAL 943Includes code for the SMB/CIFS file system. 944See 945.Xr mount_smbfs 8 946for details. 947.Em NOTE : 948You also need to enable the pseudo-device, nsmb, for the SMB 949file system to work. 950.It Cd file-system PTYFS 951Includes code for a special file system (normally mounted on 952.Pa /dev/pts ) 953in which pseudo-terminal slave devices become visible in the file system. 954See 955.Xr mount_ptyfs 8 956for details. 957.It Cd file-system TMPFS 958Includes code for the efficient memory file system, normally used over 959.Pa /tmp . 960See 961.Xr mount_tmpfs 8 962for details. 963.It Cd file-system PUFFS 964Includes kernel support for the pass-to-userspace framework file system. 965It can be used to implement file system functionality in userspace. 966See 967.Xr puffs 3 968for more details. 969This enables for example sshfs: 970.Xr mount_psshfs 8 . 971.El 972.Ss File System Options 973.Bl -ohang 974.It Cd options DISKLABEL_EI 975Enable 976.Dq Endian-Independent 977.Xr disklabel 5 978support. 979This allows a system to recognize a disklabel written in the other byte order. 980For writing, when a label already exists, its byte order is preserved. 981Otherwise, a new label is written in the native byte order. 982To specify the byte order explicitly, the 983.Fl F 984option of 985.Xr disklabel 8 986should be used with the 987.Fl B 988option in order to avoid using 989.Xr ioctl 2 , 990which results in the default behavior explained above. 991At the moment this option is restricted to the following ports: 992amd64, bebox, emips, epoc32, evbarm, i386, ibmnws, landisk, mvmeppc, prep, 993.\" riscv, 994rs6000, sandpoint, 995.\" usermode, 996xen, and zaurus; 997also to machines of the 998evbmips and evbppc ports that support 999Master Boot Record (MBR). 1000.It Cd options MAGICLINKS 1001Enables the expansion of special strings 1002.Po 1003beginning with 1004.Dq @ 1005.Pc 1006when traversing symbolic links. 1007See 1008.Xr symlink 7 1009for a list of supported strings. 1010Note that this option only controls the enabling of this feature 1011by the kernel at boot-up. 1012This feature can still be manipulated with the 1013.Xr sysctl 8 1014command regardless of the setting of this option. 1015.It Cd options NFSSERVER 1016Include the server side of the 1017.Em NFS 1018(Network File System) remote file sharing protocol. 1019Although the bulk of the code implementing 1020.Em NFS 1021is kernel based, several user level daemons are needed for it to 1022work. 1023See 1024.Xr mountd 8 1025and 1026.Xr nfsd 8 1027for details. 1028.It Cd options NVNODE=integer 1029This option sets the size of the cache used by the name-to-inode translation 1030routines, (a.k.a. the 1031.Fn namei 1032cache, though called by many other names in the kernel source). 1033By default, this cache has 1034.Dv ( NPROC + NTEXT + 100 ) 1035entries (NPROC set as 20 + 16 * MAXUSERS and NTEXT as 80 + NPROC / 8). 1036A reasonable way to derive a value of 1037.Dv NVNODE , 1038should you notice a large number of namei cache misses with a tool such as 1039.Xr systat 1 , 1040is to examine your system's current computed value with 1041.Xr sysctl 8 , 1042(which calls this parameter "kern.maxvnodes") and to increase this value 1043until either the namei cache hit rate improves or it is determined that 1044your system does not benefit substantially from an increase in the size of 1045the namei cache. 1046.It Cd options NAMECACHE_ENTER_REVERSE 1047Causes the namei cache to always enter a reverse mapping (vnode -> name) 1048as well as a normal one. 1049Normally, this is already done for directory vnodes, to speed up the getcwd 1050operation. 1051This option will cause longer hash chains in the reverse cache, and thus 1052slow down getcwd somewhat. 1053However, it does make vnode -> path translations possible in some cases. 1054For now, only useful if strict 1055.Pa /proc/#/maps 1056emulation for Linux binaries is required. 1057.El 1058.Ss Options for FFS/UFS File Systems 1059.Bl -ohang 1060.It Cd options APPLE_UFS 1061Enable support for UFS file systems created on Mac OS X. 1062.It Cd options FFS_EI 1063Enable 1064.Dq Endian-Independent 1065FFS support. 1066This allows a system to mount an FFS file system created for another 1067architecture, at a small performance cost for all FFS file systems. 1068See also 1069.Xr newfs 8 , 1070.Xr fsck_ffs 8 , 1071.Xr dumpfs 8 1072for file system byte order status and manipulation. 1073.It Cd options FFS_NO_SNAPSHOT 1074Disable support for the creation of file system internal snapshot 1075of FFS file systems. 1076Maybe useful for install media kernels, small memory systems and 1077embedded systems which don't require the snapshot support. 1078.It Cd options QUOTA 1079Enables kernel support for traditional quotas in FFS. 1080Traditional quotas store the quota information in external files and 1081require 1082.Xr quotacheck 8 1083and 1084.Xr quotaon 8 1085at boot time. 1086Traditional quotas are limited to 32-bit sizes and are at this point 1087considered a legacy feature. 1088.It Cd options QUOTA2 1089Enables kernel support for in-volume quotas in FFS. 1090The quota information is file system metadata maintained by 1091.Xr fsck 8 1092and/or WAPBL journaling. 1093MFS volumes can also use 1094.Dv QUOTA2 1095quotas; see 1096.Xr mount_mfs 8 1097for more information. 1098.It Cd options UFS_DIRHASH 1099Increase lookup performance by maintaining in-core hash tables 1100for large directories. 1101.It Cd options UFS_EXTATTR 1102Enable extended attribute support for UFS1 file systems. 1103.It Cd options WAPBL 1104Enable 1105.Dq Write Ahead Physical Block Logging file system journaling . 1106This provides rapid file system consistency checking after a system outage. 1107It also provides better general use performance over regular FFS. 1108See also 1109.Xr wapbl 4 . 1110.El 1111.Ss Options for the LFS File System 1112.Bl -ohang 1113.\" .It Cd options LFS_KERNEL_RFW 1114.\" There is no documentation for this. (XXX) 1115.\" .It Cd options LFS_QUOTA 1116.\" Enable traditional quota support for LFS. 1117.\" (It is not clear if this works.) 1118.\" .It Cd options LFS_QUOTA2 1119.\" Enable modernized 64-bit quota support for LFS. 1120.\" (This does not work yet.) 1121.It Cd options LFS_EI 1122Enable 1123.Dq Endian-Independent 1124LFS support. 1125This allows (at a small performance cost) mounting an LFS file system 1126created for another architecture. 1127.\" .It Cd options LFS_EXTATTR 1128.\" Enable extended attribute support for LFS. 1129.\" (It is not clear if this works.) 1130.It Cd options LFS_DIRHASH 1131Increase lookup performance by maintaining in-core hash tables 1132for large directories. 1133.El 1134.Ss Options for the ext2fs File System 1135.Bl -ohang 1136.It Cd options EXT2FS_SYSTEM_FLAGS 1137This option changes the behavior of the APPEND and IMMUTABLE flags 1138for a file on an 1139.Em ext2 1140file system. 1141Without this option, the superuser or owner of the file can 1142set and clear them. 1143With this option, only the superuser can set them, and 1144they can't be cleared if the securelevel is greater than 0. 1145See also 1146.Xr chflags 1 1147and 1148.Xr secmodel_securelevel 9 . 1149.El 1150.Ss Options for the NFS File System 1151.Bl -ohang 1152.It Cd options NFS_BOOT_BOOTP 1153Enable use of the BOOTP protocol (RFCs 951 and 1048) to get configuration 1154information if NFS is used to mount the root file system. 1155See 1156.Xr diskless 8 1157for details. 1158.It Cd options NFS_BOOT_BOOTSTATIC 1159Enable use of static values defined as 1160.Dq NFS_BOOTSTATIC_MYIP , 1161.Dq NFS_BOOTSTATIC_GWIP , 1162.Dq NFS_BOOTSTATIC_SERVADDR , 1163and 1164.Dq NFS_BOOTSTATIC_SERVER 1165in kernel options to get configuration information 1166if NFS is used to mount the root file system. 1167.It Cd options NFS_BOOT_DHCP 1168Same as 1169.Dq NFS_BOOT_BOOTP , 1170but use the DHCP extensions to the 1171BOOTP protocol (RFC 1541). 1172.It Cd options NFS_BOOT_BOOTP_REQFILE 1173Specifies the string sent in the bp_file field of the BOOTP/DHCP 1174request packet. 1175.It Cd options NFS_BOOT_BOOTPARAM 1176Enable use of the BOOTPARAM protocol, consisting of RARP and 1177BOOTPARAM RPC, to get configuration information if NFS 1178is used to mount the root file system. 1179See 1180.Xr diskless 8 1181for details. 1182.It Cd options NFS_BOOT_RWSIZE=value 1183Set the initial NFS read and write sizes for diskless-boot requests. 1184The normal default is 8Kbytes. 1185This option provides a way to lower the value (e.g., to 1024 bytes) 1186as a workaround for buggy network interface cards or boot PROMs. 1187Once booted, the read and write request sizes can be increased by 1188remounting the file system. 1189See 1190.Xr mount_nfs 8 1191for details. 1192.It Cd options NFS_V2_ONLY 1193Reduce the size of the NFS client code by omitting code that's only required 1194for NFSv3 and NQNFS support, leaving only that code required to use NFSv2 1195servers. 1196.It Cd options NFS_BOOT_TCP 1197Use NFS over TCP instead of the default UDP, for mounting root. 1198.El 1199.Ss Buffer queue strategy options 1200The following options enable alternative buffer queue strategies. 1201.Bl -ohang 1202.It Cd options BUFQ_READPRIO 1203Enable alternate buffer queue strategy for disk I/O. 1204In the default strategy, outstanding disk requests are ordered by 1205sector number and sent to the disk, regardless of whether the 1206operation is a read or write; this option gives priority to issuing 1207read requests over write requests. 1208Although requests may therefore be issued out of sector-order, causing 1209more seeks and thus lower overall throughput, interactive system 1210responsiveness under heavy disk I/O load may be improved, as processes 1211blocking on disk reads are serviced sooner (file writes typically 1212don't cause applications to block). 1213The performance effect varies greatly depending on the hardware, drive 1214firmware, file system configuration, workload, and desired performance 1215trade-off. 1216Systems using drive write-cache (most modern IDE disks, by default) 1217are unlikely to benefit and may well suffer; such disks acknowledge 1218writes very quickly, and optimize them internally according to 1219physical layout. 1220Giving these disks as many requests to work with as possible (the 1221standard strategy) will typically produce the best results, especially 1222if the drive has a large cache; the drive will silently complete 1223writes from cache as it seeks for reads. 1224Disks that support a large number of concurrent tagged requests (SCSI 1225disks and many hardware RAID controllers) expose this internal 1226scheduling with tagged responses, and don't block for reads; such 1227disks may not see a noticeable difference with either strategy. 1228However, if IDE disks are run with write-cache disabled for safety, 1229writes are not acknowledged until actually completed, and only one 1230request can be outstanding; a large number of small writes in one 1231locality can keep the disk busy, starving reads elsewhere on the disk. 1232Such systems are likely to see the most benefit from this option. 1233Finally, the performance interaction of this option with ffs soft 1234dependencies can be subtle, as that mechanism can drastically alter 1235the workload for file system metadata writes. 1236.It Cd options BUFQ_PRIOCSCAN 1237Enable another buffer queue strategy for disk I/O, per-priority cyclical scan. 1238.It Cd options NEW_BUFQ_STRATEGY 1239Synonym of 1240.Em BUFQ_READPRIO . 1241.El 1242.Ss Miscellaneous Options 1243.Bl -ohang 1244.It Cd options CPU_UCODE 1245Support cpu microcode loading via 1246.Xr cpuctl 8 . 1247.It Cd options MEMORY_DISK_DYNAMIC 1248This option makes the 1249.Xr md 4 1250RAM disk size dynamically sized. 1251It is incompatible with 1252.Xr mdsetimage 8 . 1253.It Cd options MEMORY_DISK_HOOKS 1254This option allows for some machine dependent functions to be called when 1255the 1256.Xr md 4 1257RAM disk driver is configured. 1258This can result in automatically loading a RAM disk from floppy on 1259open (among other things). 1260.It Cd options MEMORY_DISK_IS_ROOT 1261Forces the 1262.Xr md 4 1263RAM disk to be the root device. 1264This can only be overridden when 1265the kernel is booted in the 'ask-for-root' mode. 1266.It Cd options MEMORY_DISK_ROOT_SIZE=integer 1267Allocates the given number of 512 byte blocks as memory for the 1268.Xr md 4 1269RAM disk, to be populated with 1270.Xr mdsetimage 8 . 1271.It Cd options MEMORY_DISK_SERVER=0 1272Do not include the interface to a userland memory disk server process. 1273Per default, this option is set to 1, including the support code. 1274Useful for install media kernels. 1275.It Cd options MEMORY_DISK_RBFLAGS=value 1276This option sets the 1277.Xr reboot 2 1278flags used when booting with a memory disk as root file system. 1279Possible values include 1280.Dv RB_AUTOBOOT 1281(boot in the usual fashion - default value), and 1282.Dv RB_SINGLE 1283(boot in single-user mode). 1284.It Cd options MODULAR 1285Enables the framework for kernel modules (see 1286.Xr module 7 ) . 1287.It Cd options MODULAR_DEFAULT_AUTOLOAD 1288Enables the autoloading of kernel modules by default. 1289This sets the default value of the 1290.Em kern.module.autoload 1291.Xr sysctl 3 1292variable which may be changed at run time. 1293.It Cd options VND_COMPRESSION 1294Enables the 1295.Xr vnd 4 1296driver to also handle compressed images. 1297See 1298.Xr vndcompress 1 , 1299.Xr vnd 4 1300and 1301.Xr vnconfig 8 1302for more information. 1303.It Cd options SPLDEBUG 1304Help the kernel programmer find bugs related to the interrupt priority 1305level. 1306When 1307.Fn spllower 1308or 1309.Fn splraise 1310changes the current CPU's interrupt priority level to or from 1311.Dv IPL_HIGH , 1312record a backtrace. 1313Read 1314.Xr i386/return_address 9 1315for caveats about collecting backtraces. 1316This feature is experimental, and it is only available on i386. 1317See 1318.Pa sys/kern/subr_spldebug.c . 1319.It Cd options TFTPROOT 1320Download the root memory disk through TFTP at root mount time. 1321This enables the use of a root RAM disk without requiring it to be 1322embedded in the kernel using 1323.Xr mdsetimage 8 . 1324The RAM disk name is obtained using DHCP's filename parameter. 1325This option requires 1326.Em MEMORY_DISK_HOOKS 1327and 1328.Em MEMORY_DISK_DYNAMIC . 1329It is incompatible with 1330.Em MEMORY_DISK_ROOT_SIZE . 1331.It Cd options HZ=integer 1332On ports that support it, set the system clock frequency (see 1333.Xr hz 9 ) 1334to the supplied value. 1335Handle with care. 1336.It Cd options NTP 1337Turns on in-kernel precision timekeeping support used by software 1338implementing 1339.Em NTP 1340(Network Time Protocol, RFC 1305). 1341The 1342.Em NTP 1343option adds an in-kernel Phase-Locked Loop (PLL) for normal 1344.Em NTP 1345operation, and a Frequency-Locked Loop (FLL) for intermittently-connected 1346operation. 1347.Xr ntpd 8 1348will employ a user-level PLL when kernel support is unavailable, 1349but the in-kernel version has lower latency and more precision, and 1350so typically keeps much better time. 1351.Pp 1352The interface to the kernel 1353.Em NTP 1354support is provided by the 1355.Xr ntp_adjtime 2 1356and 1357.Xr ntp_gettime 2 1358system calls, which are intended for use by 1359.Xr ntpd 8 1360and are enabled by the option. 1361On systems with sub-microsecond resolution timers, or where (HZ/100000) 1362is not an integer, the 1363.Em NTP 1364option also enables extended-precision arithmetic to keep track of 1365fractional clock ticks at NTP time-format precision. 1366.It Cd options PPS_SYNC 1367This option enables a kernel serial line discipline for receiving time 1368phase signals from an external reference clock such as a radio clock. 1369.Po 1370The 1371.Em NTP 1372option (which see) must be on if the 1373.Em PPS_SYNC 1374option is used 1375.Pc . 1376Some reference clocks generate a Pulse Per Second (PPS) signal in 1377phase with their time source. 1378The 1379.Em PPS 1380line discipline receives this signal on either the data leads 1381or the DCD control lead of a serial port. 1382.Pp 1383.Em NTP 1384uses the PPS signal to discipline the local clock oscillator to a high 1385degree of precision (typically less than 50 microseconds in time and 13860.1 ppm in accuracy). 1387.Em PPS 1388can also generate a serial output pulse when the system receives a PPS 1389interrupt. 1390This can be used to measure the system interrupt latency and thus calibrate 1391.Em NTP 1392to account for it. 1393Using 1394.Em PPS 1395usually requires a gadget box 1396to convert from TTL to RS-232 signal levels. 1397The gadget box and PPS are described in more detail in the HTML documentation 1398for 1399.Xr ntpd 8 1400in 1401.Pa /usr/share/doc/html/ntp . 1402.Pp 1403.Nx 1404currently supports this option in 1405.Xr com 4 1406and 1407.Xr zsc 4 . 1408.It Cd options SETUIDSCRIPTS 1409Allows scripts with the setuid bit set to execute as the effective 1410user rather than the real user, just like binary executables. 1411.Pp 1412.Em NOTE : 1413Using this option will also enable 1414.Em options FDSCRIPTS 1415.It Cd options FDSCRIPTS 1416Allows execution of scripts with the execute bit set, but not the 1417read bit, by opening the file and passing the file descriptor to 1418the shell, rather than the filename. 1419.Pp 1420.Em NOTE : 1421Execute only (non-readable) scripts will have 1422.Va argv[0] 1423set to 1424.Pa /dev/fd/* . 1425What this option allows as far as security is 1426concerned, is the ability to safely ensure that the correct script 1427is run by the interpreter, as it is passed as an already open file. 1428.It Cd options RTC_OFFSET=integer 1429The kernel (and typically the hardware battery backed-up clock on 1430those machines that have one) keeps time in 1431.Em UTC 1432(Universal Coordinated Time, once known as 1433.Em GMT , 1434or Greenwich Mean Time) 1435and not in the time of the local time zone. 1436The 1437.Em RTC_OFFSET 1438option is used on some ports (such as the i386) to tell the kernel 1439that the hardware clock is offset from 1440.Em UTC 1441by the specified number of minutes. 1442This is typically used when a machine boots several operating 1443systems and one of them wants the hardware clock to run in the 1444local time zone and not in 1445.Em UTC , 1446e.g. 1447.Em RTC_OFFSET=300 1448means 1449the hardware clock is set to US Eastern Time (300 minutes behind 1450.Em UTC ) , 1451and not 1452.Em UTC . 1453(Note: 1454.Em RTC_OFFSET 1455is used to initialize a kernel variable named 1456.Va rtc_offset 1457which is the source actually used to determine the clock offset, and 1458which may be accessed via the kern.rtc_offset sysctl variable. 1459See 1460.Xr sysctl 8 1461and 1462.Xr sysctl 3 1463for details. 1464Since the kernel clock is initialized from the hardware clock very 1465early in the boot process, it is not possible to meaningfully change 1466.Va rtc_offset 1467in system initialization scripts. 1468Changing this value currently may only be done at kernel compile 1469time or by patching the kernel and rebooting). 1470.Pp 1471.Em NOTE : 1472Unfortunately, in many cases where the hardware clock 1473is kept in local time, it is adjusted for Daylight Savings 1474Time; this means that attempting to use 1475.Em RTC_OFFSET 1476to let 1477.Nx 1478coexist with such an operating system, like Windows, 1479would necessitate changing 1480.Em RTC_OFFSET 1481twice a year. 1482As such, this solution is imperfect. 1483.It Cd options MAXUPRC=integer 1484Sets the soft 1485.Dv RLIMIT_NPROC 1486resource limit, which specifies the maximum number of simultaneous 1487processes a user is permitted to run, for process 0; 1488this value is inherited by its child processes. 1489It defaults to 1490.Em CHILD_MAX , 1491which is currently defined to be 160. 1492Setting 1493.Em MAXUPRC 1494to a value less than 1495.Em CHILD_MAX 1496is not permitted, as this would result in a violation of the semantics of 1497.St -p1003.1-90 . 1498.It Cd options NOFILE=integer 1499Sets the soft 1500.Dv RLIMIT_NOFILE 1501resource limit, which specifies the maximum number of open 1502file descriptors for each process; 1503this value is inherited by its child processes. 1504It defaults to 1505.Em OPEN_MAX , 1506which is currently defined to be 128. 1507.It Cd options MAXFILES=integer 1508Sets the default value of the 1509.Em kern.maxfiles 1510sysctl variable, which indicates the maximum number of files that may 1511be open in the system. 1512.It Cd options DEFCORENAME=string 1513Sets the default value of the 1514.Em kern.defcorename 1515sysctl variable, otherwise it is set to 1516.Nm %n.core . 1517See 1518.Xr sysctl 8 1519and 1520.Xr sysctl 3 1521for details. 1522.It Cd options RASOPS_CLIPPING 1523Enables clipping within the 1524.Nm rasops 1525raster-console output system. 1526.Em NOTE : 1527only available on architectures that use 1528.Nm rasops 1529for console output. 1530.It Cd options RASOPS_SMALL 1531Removes optimized character writing code from the 1532.Nm rasops 1533raster-console output system. 1534.Em NOTE : 1535only available on architectures that use 1536.Nm rasops 1537for console output. 1538.It Cd options INCLUDE_CONFIG_FILE 1539Embeds the kernel config file used to define the kernel in the kernel 1540binary itself. 1541The embedded data also includes any files directly included by the config 1542file itself, e.g. 1543.Pa GENERIC.local 1544or 1545.Pa std.$MACHINE . 1546The embedded config file can be extracted from the resulting kernel with 1547.Xr config 1 1548.Fl x , 1549or by the following command: 1550.Bd -literal -offset indent 1551strings netbsd | sed -n 's/^_CFG_//p' | unvis 1552.Ed 1553.It Cd options INCLUDE_JUST_CONFIG 1554Similar to the above option, but includes just the actual config file, 1555not any included files. 1556.It Cd options PIPE_SOCKETPAIR 1557Use slower, but smaller socketpair(2)-based pipe implementation instead 1558of default faster, but bigger one. 1559Primarily useful for installation kernels. 1560.It Cd options USERCONF 1561Compiles in the in-kernel device configuration manager. 1562See 1563.Xr userconf 4 1564for details. 1565.It Cd options SCDEBUG_DEFAULT 1566Used with the 1567.Cd options SYSCALL_DEBUG 1568described below to choose which types of events are displayed. 1569.Pp 1570.Bl -tag -width "SCDEBUG_KERNHIST" -compact -offset indent 1571.It Dv SCDEBUG_CALLS 1572Show system call entry points. 1573.It Dv SCDEBUG_RETURNS 1574Show system call exit points. 1575.It Dv SCDEBUG_ALL 1576Show all system call requestes, including unimplemented calls. 1577.It Dv SCDEBUG_SHOWARGS 1578Show the arguments provided. 1579.It Dv SCDEBUG_KERNHIST 1580Store a restricted form of the system call debug in a kernel history 1581instead of printing it to the console. 1582This option relies upon 1583.Cd options KERNHIST . 1584.El 1585.Pp 1586The default value is 1587.Dv (SCDEBUG_CALLS|SCDEBUG_RETURNS|SCDEBUG_SHOWARGS) . 1588.It Cd options SYSCALL_DEBUG 1589Useful for debugging system call issues, usually in early single user bringup. 1590By default, writes entries to the system console for most system call events. 1591Can be configured with the 1592.Cd options SCDEBUG_DEFAULT 1593option to to use the 1594.Cd options KERNHIST 1595facility instead. 1596.It Cd options SYSCALL_STATS 1597Count the number of times each system call number is called. 1598The values can be read through the sysctl interface and displayed using 1599.Xr systat 1 . 1600.Em NOTE : 1601not yet available on all architectures. 1602.It Cd options SYSCALL_TIMES 1603Count the time spent (using 1604.Fn cpu_counter32 ) 1605in each system call. 1606.Em NOTE : 1607Using this option will also enable 1608.Cd options SYSCALL_STATS . 1609.It Cd options SYSCALL_TIMES_HASCOUNTER 1610Force use of 1611.Fn cpu_counter32 1612even if 1613.Fn cpu_hascounter 1614reports false. 1615Useful for systems where the cycle counter doesn't run at a constant rate 1616(e.g. Soekris boxes). 1617.It Cd options XSERVER_DDB 1618A supplement to XSERVER that adds support for entering 1619.Xr ddb 4 1620while in X11. 1621.It Cd options FILEASSOC 1622Support for 1623.Xr fileassoc 9 . 1624Required for 1625.Cd options PAX_SEGVGUARD 1626and 1627.Cd pseudo-device veriexec . 1628.It Cd options FILEASSOC_NHOOKS=integer 1629Number of storage slots per file for 1630.Xr fileassoc 9 . 1631Default is 4. 1632.El 1633.Ss Networking Options 1634.Bl -ohang 1635.It Cd options GATEWAY 1636Enables 1637.Em IPFORWARDING 1638and (on most ports) increases the size of 1639.Em NMBCLUSTERS . 1640In general, 1641.Em GATEWAY 1642is used to indicate that a system should act as a router, and 1643.Em IPFORWARDING 1644is not invoked directly. 1645(Note that 1646.Em GATEWAY 1647has no impact on protocols other than IP). 1648.Em GATEWAY 1649option also compiles IPv4 and IPv6 fast forwarding code into the kernel. 1650.It Cd options IPFORWARDING=value 1651If 1652.Em value 1653is 1 this enables IP routing behavior. 1654If 1655.Em value 1656is 0 (the default), it disables it. 1657The 1658.Em GATEWAY 1659option sets this to 1 automatically. 1660With this option enabled, the machine will forward IP datagrams destined 1661for other machines between its interfaces. 1662Note that even without this option, the kernel will 1663still forward some packets (such as source routed packets) \(em removing 1664.Em GATEWAY 1665and 1666.Em IPFORWARDING 1667is insufficient to stop all routing through a bastion host on a 1668firewall \(em source routing is controlled independently. 1669Note that IP forwarding may be turned on and off independently of the 1670setting of the 1671.Em IPFORWARDING 1672option through the use of the 1673.Em net.inet.ip.forwarding 1674sysctl variable. 1675If 1676.Em net.inet.ip.forwarding 1677is 1, IP forwarding is on. 1678See 1679.Xr sysctl 8 1680and 1681.Xr sysctl 3 1682for details. 1683.It Cd options IFA_STATS 1684Tells the kernel to maintain per-address statistics on bytes sent 1685and received over (currently) Internet and AppleTalk addresses. 1686.\"This can be a fairly expensive operation, so you probably want to 1687.\"keep this disabled. 1688The option is not recommended as it degrades system stability. 1689.It Cd options IFQ_MAXLEN=value 1690Increases the allowed size of the network interface packet queues. 1691The default queue size is 50 packets, and you do not normally need 1692to increase it. 1693.It Cd options IPSELSRC 1694Includes support for source-address selection policies. 1695See 1696.Xr in_getifa 9 . 1697.It Cd options MROUTING 1698Includes support for IP multicast routers. 1699You certainly want 1700.Em INET 1701with this. 1702Multicast routing is controlled by the 1703.Xr mrouted 8 1704daemon. 1705See also option 1706.Cd PIM . 1707.It Cd options PIM 1708Includes support for Protocol Independent Multicast (PIM) routing. 1709You need 1710.Em MROUTING 1711and 1712.Em INET 1713with this. 1714Software using this can be found e.g. in 1715.Pa pkgsrc/net/xorp . 1716.It Cd options INET 1717Includes support for the TCP/IP protocol stack. 1718You almost certainly want this. 1719See 1720.Xr inet 4 1721for details. 1722.It Cd options INET6 1723Includes support for the IPv6 protocol stack. 1724See 1725.Xr inet6 4 1726for details. 1727Unlike 1728.Em INET , 1729.Em INET6 1730enables multicast routing code as well. 1731This option requires 1732.Em INET 1733at this moment, but it should not. 1734.It Cd options ND6_DEBUG 1735The option sets the default value of net.inet6.icmp6.nd6_debug to 1, 1736for debugging IPv6 neighbor discovery protocol handling. 1737See 1738.Xr sysctl 3 1739for details. 1740.It Cd options IPSEC 1741Includes support for the IPsec protocol, using the implementation derived from 1742.Ox , 1743relying on 1744.Xr opencrypto 9 1745to carry out cryptographic operations. 1746See 1747.Xr ipsec 4 1748for details. 1749.It Cd options IPSEC_DEBUG 1750Enables debugging code in IPsec stack. 1751See 1752.Xr ipsec 4 1753for details. 1754The 1755.Cd IPSEC 1756option includes support for IPsec Network Address Translator traversal 1757(NAT-T), as described in RFCs 3947 and 3948. 1758This feature might be patent-encumbered in some countries. 1759.It Cd options ALTQ 1760Enabled ALTQ (Alternate Queueing). 1761For simple rate-limiting, use 1762.Xr tbrconfig 8 1763to set up the interface transmission rate. 1764To use queueing disciplines, their appropriate kernel options should also 1765be defined (documented below). 1766Queueing disciplines are managed by 1767.Xr altqd 8 . 1768See 1769.Xr altq 9 1770for details. 1771.It Cd options ALTQ_HFSC 1772Include support for ALTQ-implemented HFSC (Hierarchical Fair Service Curve) 1773module. 1774HFSC supports both link-sharing and guaranteed real-time services. 1775HFSC employs a service curve based QoS model, and its unique feature 1776is an ability to decouple delay and bandwidth allocation. 1777Requires 1778.Em ALTQ_RED 1779to use the RED queueing discipline on HFSC classes, or 1780.Em ALTQ_RIO 1781to use the RIO queueing discipline on HFSC classes. 1782This option assumes 1783.Em ALTQ . 1784.It Cd options ALTQ_PRIQ 1785Include support for ALTQ-implemented PRIQ (Priority Queueing). 1786PRIQ implements a simple priority-based queueing discipline. 1787A higher priority class is always served first. 1788Requires 1789.Em ALTQ_RED 1790to use the RED queueing discipline on HFSC classes, or 1791.Em ALTQ_RIO 1792to use the RIO queueing discipline on HFSC classes. 1793This option assumes 1794.Em ALTQ . 1795.It Cd options ALTQ_WFQ 1796Include support for ALTQ-implemented WFQ (Weighted Fair Queueing). 1797WFQ implements a weighted-round robin scheduler for a set of queues. 1798A weight can be assigned to each queue to give a different proportion 1799of the link capacity. 1800A hash function is used to map a flow to one of a set of queues. 1801This option assumes 1802.Em ALTQ . 1803.It Cd options ALTQ_FIFOQ 1804Include support for ALTQ-implemented FIFO queueing. 1805FIFOQ is a simple drop-tail FIFO (First In, First Out) queueing discipline. 1806This option assumes 1807.Em ALTQ . 1808.It Cd options ALTQ_RIO 1809Include support for ALTQ-implemented RIO (RED with In/Out). 1810The original RIO has 2 sets of RED parameters; one for in-profile 1811packets and the other for out-of-profile packets. 1812At the ingress of the network, profile meters tag packets as IN or 1813OUT based on contracted profiles for customers. 1814Inside the network, IN packets receive preferential treatment by 1815the RIO dropper. 1816ALTQ/RIO has 3 drop precedence levels defined for the Assured Forwarding 1817PHB of DiffServ (RFC 2597). 1818This option assumes 1819.Em ALTQ . 1820.It Cd options ALTQ_BLUE 1821Include support for ALTQ-implemented Blue buffer management. 1822Blue is another active buffer management mechanism. 1823This option assumes 1824.Em ALTQ . 1825.It Cd options ALTQ_FLOWVALVE 1826Include support for ALTQ-implemented Flowvalve. 1827Flowvalve is a simple implementation of a RED penalty box that identifies 1828and punishes misbehaving flows. 1829This option requires 1830.Em ALTQ_RED 1831and assumes 1832.Em ALTQ . 1833.It Cd options ALTQ_CDNR 1834Include support for ALTQ-implemented CDNR (diffserv traffic conditioner) 1835packet marking/manipulation. 1836Traffic conditioners are components to meter, mark, or drop incoming 1837packets according to some rules. 1838As opposed to queueing disciplines, traffic conditioners handle incoming 1839packets at an input interface. 1840This option assumes 1841.Em ALTQ . 1842.It Cd options ALTQ_NOPCC 1843Disables use of processor cycle counter to measure time in ALTQ. 1844This option should be defined for a non-Pentium i386 CPU which does not 1845have TSC, SMP (per-CPU counters are not in sync), or power management 1846which affects processor cycle counter. 1847This option assumes 1848.Em ALTQ . 1849.It Cd options ALTQ_IPSEC 1850Include support for IPsec in IPv4 ALTQ. 1851This option assumes 1852.Em ALTQ . 1853.It Cd options ALTQ_JOBS 1854Include support for ALTQ-implemented JoBS (Joint Buffer Management 1855and Scheduling). 1856This option assumes 1857.Em ALTQ . 1858.It Cd options ALTQ_AFMAP 1859Include support for an undocumented ALTQ feature that is used to map an IP 1860flow to an ATM VC (Virtual Circuit). 1861This option assumes 1862.Em ALTQ . 1863.It Cd options ALTQ_LOCALQ 1864Include support for ALTQ-implemented local queues. 1865Its practical use is undefined. 1866Assumes 1867.Em ALTQ . 1868.It Cd options SUBNETSARELOCAL 1869Sets default value for net.inet.ip.subnetsarelocal variable, which 1870controls whether non-directly-connected subnets of connected networks 1871are considered "local" for purposes of choosing the MSS for a TCP 1872connection. 1873This is mostly present for historic reasons and completely irrelevant if 1874you enable Path MTU discovery. 1875.It Cd options HOSTZEROBROADCAST 1876Sets default value for net.inet.ip.hostzerobroadcast variable, which 1877controls whether the zeroth host address of each connected subnet is 1878also considered a broadcast address. 1879Default value is "1", for compatibility with old systems; if this is 1880set to zero on all hosts on a subnet, you should be able to fit an extra 1881host per subnet on the 1882".0" address. 1883.It Cd options MCLSHIFT=value 1884This option is the base-2 logarithm of the size of mbuf clusters. 1885The 1886.Bx 1887networking stack keeps network packets in a linked 1888list, or chain, of kernel buffer objects called mbufs. 1889The system provides larger mbuf clusters as an optimization for 1890large packets, instead of using long chains for large packets. 1891The mbuf cluster size, 1892or 1893.Em MCLBYTES , 1894must be a power of two, and is computed as two raised to the power 1895.Em MCLSHIFT . 1896On systems with Ethernet network adapters, 1897.Em MCLSHIFT 1898is often set to 11, giving 2048-byte mbuf clusters, large enough to 1899hold a 1500-byte Ethernet frame in a single cluster. 1900Systems with network interfaces supporting larger frame sizes like 1901ATM, FDDI, or HIPPI may perform better with 1902.Em MCLSHIFT 1903set to 12 or 13, giving mbuf cluster sizes of 4096 and 8192 bytes, 1904respectively. 1905.It Cd options NETATALK 1906Include support for the AppleTalk protocol stack. 1907The kernel provides provision for the 1908.Em Datagram Delivery Protocol 1909(DDP), providing SOCK_DGRAM support and AppleTalk routing. 1910This stack is used by the 1911.Em NETATALK 1912package, which adds support for AppleTalk server services via user 1913libraries and applications. 1914.It Cd options BLUETOOTH 1915Include support for the Bluetooth protocol stack. 1916See 1917.Xr bluetooth 4 1918for details. 1919.It Cd options IPNOPRIVPORTS 1920Normally, only root can bind a socket descriptor to a so-called 1921.Dq privileged 1922TCP port, that is, a port number in the range 0-1023. 1923This option eliminates those checks from the kernel. 1924This can be useful if there is a desire to allow daemons without 1925privileges to bind those ports, e.g., on firewalls. 1926The security tradeoffs in doing this are subtle. 1927This option should only be used by experts. 1928.It Cd options TCP_DEBUG 1929Record the last 1930.Em TCP_NDEBUG 1931TCP packets with SO_DEBUG set, and decode to the console if 1932.Em tcpconsdebug 1933is set. 1934.It Cd options TCP_NDEBUG 1935Number of packets to record for 1936.Em TCP_DEBUG . 1937Defaults to 100. 1938.It Cd options TCP_SENDSPACE=value 1939.It Cd options TCP_RECVSPACE=value 1940These options set the max TCP window size to other sizes than the default. 1941The TCP window sizes can be altered via 1942.Xr sysctl 8 1943as well. 1944.It Cd options TCP_INIT_WIN=value 1945This option sets the initial TCP window size for non-local connections, 1946which is used when the transmission starts. 1947The default size is 1, but if the machine should act more aggressively, 1948the initial size can be set to some other value. 1949The initial TCP window size can be set via 1950.Xr sysctl 8 1951as well. 1952.It Cd options TCP_SIGNATURE 1953Enable MD5 TCP signatures (RFC 2385) to protect BGP sessions. 1954.It Cd options IPFILTER_LOG 1955This option, in conjunction with 1956.Em pseudo-device ipfilter , 1957enables logging of IP packets using IP-Filter. 1958.It Cd options IPFILTER_LOOKUP 1959This option enables the 1960IP-Filter 1961.Xr ippool 8 1962functionality to be enabled. 1963.It Cd options IPFILTER_COMPAT 1964This option enables older IP-Filter binaries to work. 1965.It Cd options IPFILTER_DEFAULT_BLOCK 1966This option sets the default policy of IP-Filter. 1967If it is set, IP-Filter will block packets by default. 1968.It Cd options BRIDGE_IPF 1969This option causes 1970.Em bridge 1971devices to use the IP and/or IPv6 filtering hooks, forming 1972a link-layer filter that uses protocol-layer rules. 1973This option assumes the presence of 1974.Em pseudo-device ipfilter . 1975.It Cd options MBUFTRACE 1976This option can help track down mbuf leaks. 1977When enabled, mbufs are tagged with the devices and protocols using them, 1978which slightly decreases network performance. 1979This additional information can be viewed with 1980.Xr netstat 1 : 1981.Dl Ic netstat Fl mssv 1982Not all devices or protocols support this option. 1983.El 1984.Ss Sysctl Related Options 1985.Bl -ohang 1986.It Cd options SYSCTL_DISALLOW_CREATE 1987Disallows the creation or deletion of nodes from the sysctl tree, as 1988well as the assigning of descriptions to nodes that lack them, by any 1989process. 1990These operations are still available to kernel sub-systems, including 1991loadable kernel modules. 1992.It Cd options SYSCTL_DISALLOW_KWRITE 1993Prevents processes from adding nodes to the sysctl tree that make 1994existing kernel memory areas writable. 1995Sections of kernel memory can still be read and new nodes that own 1996their own data may still be writable. 1997.It Cd options SYSCTL_DEBUG_SETUP 1998Causes the SYSCTL_SETUP routines to print a brief message when they 1999are invoked. 2000This is merely meant as an aid in determining the order in which 2001sections of the tree are created. 2002.It Cd options SYSCTL_DEBUG_CREATE 2003Prints a message each time 2004.Fn sysctl_create , 2005the function that adds nodes to the tree, is called. 2006.It Cd options SYSCTL_INCLUDE_DESCR 2007Causes the kernel to include short, human readable descriptions for 2008nodes in the sysctl tree. 2009The descriptions can be retrieved programmatically (see 2010.Xr sysctl 3 ) , 2011or by the sysctl binary itself (see 2012.Xr sysctl 8 ) . 2013The descriptions are meant to give an indication of the purpose and/or 2014effects of a given node's value, not replace the documentation for the 2015given subsystem as a whole. 2016.El 2017.Ss System V IPC Options 2018.Bl -ohang 2019.It Cd options SYSVMSG 2020Includes support for 2021.At V 2022style message queues. 2023See 2024.Xr msgctl 2 , 2025.Xr msgget 2 , 2026.Xr msgrcv 2 , 2027.Xr msgsnd 2 . 2028.It Cd options SYSVSEM 2029Includes support for 2030.At V 2031style semaphores. 2032See 2033.Xr semctl 2 , 2034.Xr semget 2 , 2035.Xr semop 2 . 2036.It Cd options SEMMNI=value 2037Sets the number of 2038.At V 2039style semaphore identifiers. 2040The GENERIC config file for your port will have the default. 2041.It Cd options SEMMNS=value 2042Sets the number of 2043.At V 2044style semaphores in the system. 2045The GENERIC config file for your port will have the default. 2046.It Cd options SEMUME=value 2047Sets the maximum number of undo entries per process for 2048.At V 2049style semaphores. 2050The GENERIC config file for your port will have the default. 2051.It Cd options SEMMNU=value 2052Sets the number of undo structures in the system for 2053.At V 2054style semaphores. 2055The GENERIC config file for your port will have the default. 2056.It Cd options SYSVSHM 2057Includes support for 2058.At V 2059style shared memory. 2060See 2061.Xr shmat 2 , 2062.Xr shmctl 2 , 2063.Xr shmdt 2 , 2064.Xr shmget 2 . 2065.It Cd options SHMMAXPGS=value 2066Sets the maximum number of 2067.At V 2068style shared memory pages that are available through the 2069.Xr shmget 2 2070system call. 2071Default value is 1024 on most ports. 2072See 2073.Pa /usr/include/machine/vmparam.h 2074for the default. 2075.El 2076.Ss VM Related Options 2077.Bl -ohang 2078.It Cd options NMBCLUSTERS=value 2079The number of mbuf clusters the kernel supports. 2080Mbuf clusters are MCLBYTES in size (usually 2k). 2081This is used to compute the size of the kernel VM map 2082.Em mb_map , 2083which maps mbuf clusters. 2084Default on most ports is 1024 (2048 with 2085.Dq options GATEWAY 2086). 2087See 2088.Pa /usr/include/machine/param.h 2089for exact default information. 2090Increase this value if you get 2091.Dq mclpool limit reached 2092messages. 2093.It Cd options NKMEMPAGES=value 2094.It Cd options NKMEMPAGES_MIN=value 2095.It Cd options NKMEMPAGES_MAX=value 2096Size of kernel VM map 2097.Em kmem_map , 2098in PAGE_SIZE-sized chunks (the VM page size; this value may be read 2099from the 2100.Xr sysctl 8 2101variable 2102.Em hw.pagesize 2103). 2104This VM map is used to map the kernel malloc arena. 2105The kernel attempts to auto-size this map based on the amount of 2106physical memory in the system. 2107Platform-specific code may place bounds on this computed size, 2108which may be viewed with the 2109.Xr sysctl 8 2110variable 2111.Em vm.nkmempages . 2112See 2113.Pa /usr/include/machine/param.h 2114for the default upper and lower bounds. 2115The related options 2116.Sq NKMEMPAGES_MIN 2117and 2118.Sq NKMEMPAGES_MAX 2119allow the bounds to be overridden in the kernel configuration file. 2120These options are provided in the event the computed value is 2121insufficient resulting in an 2122.Dq out of space in kmem_map 2123panic. 2124.It Cd options SB_MAX=value 2125Sets the max size in bytes that a socket buffer is allowed to occupy. 2126The default is 256k, but sometimes it needs to be increased, for example 2127when using large TCP windows. 2128This option can be changed via 2129.Xr sysctl 8 2130as well. 2131.It Cd options SOMAXKVA=value 2132Sets the maximum size of kernel virtual memory that the socket buffers 2133are allowed to use. 2134The default is 16MB, but in situations where for example large TCP 2135windows are used this value must also be increased. 2136This option can be changed via 2137.Xr sysctl 8 2138as well. 2139.It Cd options BUFCACHE=value 2140Size of the buffer cache as a percentage of total available RAM. 2141Ignored if BUFPAGES is also specified. 2142.It Cd options NBUF=value 2143Sets the number of buffer headers available, i.e., the number of 2144open files that may have a buffer cache entry. 2145Each buffer header 2146requires MAXBSIZE (machine dependent, but usually 65536) bytes. 2147The default value is machine dependent, but is usually equal to the 2148value of BUFPAGES. 2149.It Cd options BUFPAGES=value 2150These options set the number of pages available for the buffer cache. 2151Their default value is a machine dependent value, often calculated as 2152between 5% and 10% of total available RAM. 2153.It Cd options MAXTSIZ=bytes 2154Sets the maximum size limit of a process' text segment. 2155See 2156.Pa /usr/include/machine/vmparam.h 2157for the port-specific default. 2158.It Cd options DFLDSIZ=bytes 2159Sets the default size limit of a process' data segment, the value that 2160will be returned as the soft limit for 2161.Dv RLIMIT_DATA 2162(as returned by 2163.Xr getrlimit 2 ) . 2164See 2165.Pa /usr/include/machine/vmparam.h 2166for the port-specific default. 2167.It Cd options MAXDSIZ=bytes 2168Sets the maximum size limit of a process' data segment, the value that 2169will be returned as the hard limit for 2170.Dv RLIMIT_DATA 2171(as returned by 2172.Xr getrlimit 2 ) . 2173See 2174.Pa /usr/include/machine/vmparam.h 2175for the port-specific default. 2176.It Cd options DFLSSIZ=bytes 2177Sets the default size limit of a process' stack segment, the value that 2178will be returned as the soft limit for 2179.Dv RLIMIT_STACK 2180(as returned by 2181.Xr getrlimit 2 ) . 2182See 2183.Pa /usr/include/machine/vmparam.h 2184for the port-specific default. 2185.It Cd options MAXSSIZ=bytes 2186Sets the maximum size limit of a process' stack segment, the value that 2187will be returned as the hard limit for 2188.Dv RLIMIT_STACK 2189(as returned by 2190.Xr getrlimit 2 ) . 2191See 2192.Pa /usr/include/machine/vmparam.h 2193for the port-specific default. 2194.It Cd options DUMP_ON_PANIC=integer 2195Defaults to one. 2196If set to zero, the kernel will not dump to the dump device when 2197it panics, though dumps can still be forced via 2198.Xr ddb 4 2199with the 2200.Dq sync 2201command. 2202Note that this sets the value of the 2203.Em kern.dump_on_panic 2204.Xr sysctl 3 2205variable which may be changed at run time \(em see 2206.Xr sysctl 8 2207for details. 2208.It Cd options USE_TOPDOWN_VM 2209User space memory allocations (as made by 2210.Xr mmap 2 ) 2211will be arranged in a 2212.Dq top down 2213fashion instead of the traditional 2214.Dq upwards from MAXDSIZ \&+ vm_daddr 2215method. 2216This includes the placement of 2217.Xr ld.so 1 . 2218Arranging memory in this manner allows either (or both of) the heap or 2219.Xr mmap 2 2220allocated space to grow larger than traditionally possible. 2221This option is not available on all ports, but is instead expected to be 2222offered on a port-by-port basis, after which some ports will commit to 2223using it by default. 2224See the files 2225.Pa /usr/include/uvm/uvm_param.h 2226for some implementation details, and 2227.Pa /usr/include/machine/vmparam.h 2228for port specific details including availability. 2229.It Cd options VMSWAP 2230Enable paging device/file support. 2231This option is on by default. 2232.It Cd options PDPOLICY_CLOCKPRO 2233Use CLOCK-Pro, an alternative page replace policy. 2234.El 2235.Ss Security Options 2236.Bl -ohang 2237.It Cd options INSECURE 2238Initializes the kernel security level with \-1 instead of 0. 2239This means that the system always starts in secure level \-1 mode, even when 2240running multiuser, unless the securelevel variable is set to value > \-1 in 2241.Pa /etc/rc.conf . 2242In this case the kernel security level will be raised to that value when the 2243.Pa /etc/rc.d/securelevel 2244script is run during system startup. 2245See the manual page for 2246.Xr init 8 2247for details on the implications of this. 2248The kernel secure level may manipulated by the superuser by altering the 2249.Em kern.securelevel 2250.Xr sysctl 3 2251variable (the secure level may only be lowered by a call from process ID 1, 2252i.e., 2253.Xr init 8 ) . 2254See also 2255.Xr secmodel_securelevel 9 , 2256.Xr sysctl 8 2257and 2258.Xr sysctl 3 . 2259.It Cd options VERIFIED_EXEC_FP_SHA256 2260Enables support for SHA256 hashes in Veriexec. 2261.It Cd options VERIFIED_EXEC_FP_SHA384 2262Enables support for SHA384 hashes in Veriexec. 2263.It Cd options VERIFIED_EXEC_FP_SHA512 2264Enables support for SHA512 hashes in Veriexec. 2265.It Cd options PAX_MPROTECT=value 2266Enables PaX MPROTECT, 2267.Xr mprotect 2 2268restrictions from the PaX project. 2269.Pp 2270The 2271.Ar value 2272is the default value for the 2273.Em global 2274knob, see 2275.Xr sysctl 3 . 2276If 0, PaX MPROTECT will be enabled only if explicitly set on programs 2277using 2278.Xr paxctl 8 . 2279If 1, PaX MPROTECT will be enabled for all programs. 2280Programs can be exempted using 2281.Xr paxctl 8 . 2282.Pp 2283See 2284.Xr security 7 2285for more details. 2286.It Cd options PAX_SEGVGUARD=value 2287Enables PaX Segvguard. 2288Requires 2289.Cd options FILEASSOC . 2290.Pp 2291The 2292.Ar value 2293is the default value for the 2294.Em global 2295knob, see 2296.Xr sysctl 3 . 2297If 0, PaX Segvguard will be enabled only if explicitly set on programs 2298using 2299.Xr paxctl 8 . 2300If 1, PaX Segvguard will be enabled to all programs, and exemption can 2301be done using 2302.Xr paxctl 8 . 2303.Pp 2304See 2305.Xr security 7 2306for more details. 2307.It Cd options PAX_ASLR=value 2308Enables PaX ASLR. 2309.Pp 2310The 2311.Ar value 2312is the default value for the 2313.Em global 2314knob, see 2315.Xr sysctl 3 . 2316If 0, PaX ASLR will be enabled only if explicitly set on programs 2317using 2318.Xr paxctl 8 . 2319If 1, PaX ASLR will be enabled to all programs, and exemption can 2320be done using 2321.Xr paxctl 8 . 2322.Pp 2323See 2324.Xr security 7 2325for more details. 2326.It Cd options USER_VA0_DISABLE_DEFAULT=value 2327Sets the initial value of the flag which controls whether user programs 2328can map virtual address 0. 2329The flag can be changed at runtime by 2330.Xr sysctl 3 . 2331.It Cd options KASAN 2332Enables Kernel Address Sanitizer. 2333.Em NOTE : 2334not available on all architectures. 2335.It Cd options KASLR 2336Enables Kernel ASLR. 2337This randomizes the location of the kernel image in memory. 2338.Em NOTE : 2339not available on all architectures. 2340.It Cd options SVS 2341Enables Separate Virtual Space. 2342On architectures that are designed to function with a shared address 2343space, this option explicitly isolates the kernel and user spaces. 2344.Em NOTE : 2345not available on all architectures. 2346.El 2347.Ss amiga-specific Options 2348.Bl -ohang 2349.It Cd options BB060STUPIDROM 2350When the bootloader (which passes AmigaOS ROM information) claims 2351we have a 68060 CPU without FPU, go look into the Processor 2352Configuration Register (PCR) to find out. 2353You need this with Amiga ROMs up to (at least) V40.xxx (OS3.1), 2354when you boot via the bootblocks and don't have a DraCo. 2355.It Cd options IOBZCLOCK=frequency 2356The IOBlix boards come with two different serial master clocks: older ones 2357use 24 MHz, newer ones use 22.1184 MHz. 2358The driver normally assumes the latter. 2359If your board uses 24 MHz, you can recompile your kernel with 2360options IOBZCLOCK=24000000 2361or patch the kernel variable iobzclock to the same value. 2362.It Cd options LIMITMEM=value 2363If there, limit the part of the first memory bank used by 2364.Nx 2365to value megabytes. 2366Default is unlimited. 2367.It Cd options P5PPC68KBOARD 2368Add special support for Phase5 mixed 68k+PPC boards. 2369Currently, this only affects rebooting from 2370.Nx 2371and is only needed on 68040+PPC, not on 237268060+PPC; without this, affected machines will hang after 2373.Nx 2374has shut 2375down and will only restart after a keyboard reset or a power cycle. 2376.El 2377.Ss atari-specific Options 2378.Bl -ohang 2379.It Cd options DISKLABEL_AHDI 2380Include support for AHDI (native Atari) disklabels. 2381.It Cd options DISKLABEL_NBDA 2382Include support for 2383.Nx Ns /atari 2384labels. 2385If you don't set this option, it will be set automatically. 2386.Nx Ns /atari 2387will not work without it. 2388.It Cd options FALCON_SCSI 2389Include support for the 5380-SCSI configuration as found on the Falcon. 2390.It Cd options RELOC_KERNEL 2391If set, the kernel will relocate itself to TT-RAM, if possible. 2392This will give you a slightly faster system. 2393.Em Beware 2394that on some TT030 systems, 2395the system will frequently dump with MMU-faults with this option enabled. 2396.It Cd options SERCONSOLE 2397Allow the modem1-port to act as the system-console. 2398A carrier should be active on modem1 during system boot to active 2399the console functionality. 2400.It Cd options TT_SCSI 2401Include support for the 5380-SCSI configuration as found on the TT030 2402and Hades. 2403.El 2404.Ss i386-specific Options 2405.Bl -ohang 2406.It Cd options CPURESET_DELAY=value 2407Specifies the time (in millisecond) to wait before doing a hardware reset 2408in the last phase of a reboot. 2409This gives the user a chance to see error messages from the shutdown 2410operations (like NFS unmounts, buffer cache flush, etc ...). 2411Setting this to 0 will disable the delay. 2412Default is 2 seconds. 2413.It Cd options USER_LDT 2414Include i386-specific system calls for modifying the local descriptor table, 2415used by Windows emulators. 2416.It Cd options PAE 2417Enable PAE (Physical Address Extension) mode. 2418PAE permits up to 36 bits physical addressing (64GB of physical 2419memory), and turns physical addresses to 64 bits entities in the 2420memory management subsystem. 2421Userland virtual address space remains at 32 bits (4GB). 2422PAE mode is required to enable the NX/XD (No-eXecute/eXecute Disable) 2423bit for pages, which allows marking certain ones as not being executable. 2424Any attempt to execute code from such a page will raise an exception. 2425.It Cd options REALBASEMEM=integer 2426Overrides the base memory size passed in from the boot block. 2427(Value given in kilobytes.) 2428Use this option only if the boot block reports the size incorrectly. 2429(Note that some BIOSes put the extended BIOS 2430data area at the top of base memory, and therefore report a smaller 2431base memory size to prevent programs overwriting it. 2432This is correct behavior, and you should not use the 2433.Em REALBASEMEM 2434option to access this memory). 2435.It Cd options SPECTRE_V2_GCC_MITIGATION=1 2436Enable GCC-specific Spectre variant 2 mitigations. 2437For 32-bit kernels this means these options: 2438.Bd -literal -offset indent 2439-mindirect-branch=thunk -mindirect-branch-register 2440.Ed 2441.Pp 2442For 64-bit kernels this means these options: 2443.Bd -literal -offset indent 2444-mindirect-branch=thunk-inline -mindirect-branch-register 2445.Ed 2446.It Cd options REALEXTMEM=integer 2447Overrides the extended memory size passed in from the boot block. 2448(Value given in kilobytes. 2449Extended memory does not include the first megabyte.) 2450Use this option only if the boot block reports the size incorrectly. 2451.It Cd options CYRIX_CACHE_WORKS 2452Relevant only to the Cyrix 486DLC CPU. 2453This option is used to turn on the cache in hold-flush mode. 2454It is not turned on by default because it is known to have problems in 2455certain motherboard implementations. 2456.It Cd options CYRIX_CACHE_REALLY_WORKS 2457Relevant only to the Cyrix 486DLC CPU. 2458This option is used to turn on the cache in write-back mode. 2459It is not turned on by default because it is known to have problems in 2460certain motherboard implementations. 2461In order for this option to take effect, option 2462.Em CYRIX_CACHE_WORKS 2463must also be specified. 2464.It Cd options PCIBIOS 2465Enable support for initializing the PCI bus using information from 2466the BIOS. 2467See 2468.Xr pcibios 4 2469for details. 2470.It Cd options MTRR 2471Include support for accessing MTRR registers from user-space. 2472See 2473.Xr i386_get_mtrr 2 . 2474.It Cd options BEEP_ONHALT 2475Make the system speaker emit several beeps when it is completely safe to 2476power down the computer after a 2477.Xr halt 8 2478command. 2479Requires 2480.Xr sysbeep 4 2481support. 2482.It Cd options BEEP_ONHALT_COUNT=times 2483Number of times to beep the speaker when 2484.Cd options BEEP_ONHALT 2485is enabled. 2486Defaults to 3. 2487.It Cd options BEEP_ONHALT_PITCH=hz 2488The tone frequency used when 2489.Cd options BEEP_ONHALT 2490option, in hertz. 2491Defaults to 1500. 2492.It Cd options BEEP_ONHALT_PERIOD=msecs 2493The duration of each beep when 2494.Cd options BEEP_ONHALT 2495is enabled, in milliseconds. 2496Defaults to 250. 2497.It Cd options MULTIBOOT 2498Makes the kernel Multiboot-compliant, allowing it to be booted through 2499a Multiboot-compliant boot manager such as GRUB. 2500See 2501.Xr multiboot 8 2502for more information. 2503.It Cd options SPLASHSCREEN 2504Display a splash screen during boot. 2505.El 2506.Ss isa-specific Options 2507Options specific to 2508.Xr isa 4 2509busses. 2510.Bl -ohang 2511.It Cd options PCIC_ISA_ALLOC_IOBASE=address, PCIC_ISA_ALLOC_IOSIZE=size 2512Control the section of IO bus space used for PCMCIA bus space mapping. 2513Ideally the probed defaults are satisfactory, however in practice 2514that is not always the case. 2515See 2516.Xr pcmcia 4 2517for details. 2518.It Cd options PCIC_ISA_INTR_ALLOC_MASK=mask 2519Controls the allowable interrupts that may be used for PCMCIA 2520devices. 2521This mask is a logical-or of power-of-2s of allowable interrupts: 2522.Bd -literal -offset 04n 2523.Em "IRQ Val IRQ Val IRQ Val IRQ Val" 2524 0 0x0001 4 0x0010 8 0x0100 12 0x1000 2525 1 0x0002 5 0x0020 9 0x0200 13 0x2000 2526 2 0x0004 6 0x0040 10 0x0400 14 0x4000 2527 3 0x0008 7 0x0080 11 0x0800 15 0x8000 2528.Ed 2529.It Cd options PCKBC_CNATTACH_SELFTEST 2530Perform a self test of the keyboard controller before attaching it as a 2531console. 2532This might be necessary on machines where we boot on cold iron, and 2533pckbc refuses to talk until we request a self test. 2534Currently only the netwinder port uses it. 2535.It Cd options PCKBD_CNATTACH_MAY_FAIL 2536If this option is set the PS/2 keyboard will not be used as the console 2537if it cannot be found during boot. 2538This allows other keyboards, like USB, to be the console keyboard. 2539.It Cd options PCKBD_LAYOUT=layout 2540Sets the default keyboard layout, see 2541.Xr pckbd 4 . 2542.El 2543.Ss m68k-specific Options 2544.Bl -ohang 2545.It Cd options FPU_EMULATE 2546Include support for MC68881/MC68882 emulator. 2547.It Cd options FPSP 2548Include support for 68040 floating point. 2549.It Cd options M68020,M68030,M68040,M68060 2550Include support for a specific CPU, 2551at least one (the one you are using) should be specified. 2552.It Cd options M060SP 2553Include software support for 68060. 2554This provides emulation of unimplemented 2555integer instructions as well as emulation of unimplemented floating point 2556instructions and data types and software support for floating point traps. 2557.El 2558.Ss powerpc-specific Options (OEA Only) 2559.Bl -ohang 2560.It Cd options PMAP_MEMLIMIT=value 2561Limit the amount of memory seen by the kernel to 2562.Ar value 2563bytes. 2564.It Cd options PTEGCOUNT=value 2565Specify the size of the page table as 2566.Ar value 2567PTE groups. 2568Normally, one PTEG is allocated per physical page frame. 2569.El 2570.Ss sparc-specific Options 2571.Bl -ohang 2572.It Cd options AUDIO_DEBUG 2573Enable simple event debugging of the logging of the 2574.Xr audio 4 2575device. 2576.It Cd options BLINK 2577Enable blinking of LED. 2578Blink rate is full cycle every N seconds for 2579N < then current load average. 2580See 2581.Xr getloadavg 3 . 2582.\" .It Cd options COLORFONT_CACHE 2583.\" What does this do? 2584.It Cd options COUNT_SW_LEFTOVERS 2585Count how many times the sw SCSI device has left 3, 2, 1 and 0 in the 2586sw_3_leftover, sw_2_leftover, sw_1_leftover, and sw_0_leftover 2587variables accessible from 2588.Xr ddb 4 . 2589See 2590.Xr sw 4 . 2591.It Cd options DEBUG_ALIGN 2592Adds debugging messages calls when user-requested alignment fault 2593handling happens. 2594.It Cd options DEBUG_EMUL 2595Adds debugging messages calls for emulated floating point and 2596alignment fixing operations. 2597.It Cd options EXTREME_DEBUG 2598Adds debugging functions callable from 2599.Xr ddb 4 . 2600The debug_pagetables, test_region and print_fe_map 2601functions print information about page tables for the SUN4M 2602platforms only. 2603.It Cd options EXTREME_EXTREME_DEBUG 2604Adds extra info to 2605.Em options EXTREME_DEBUG . 2606.It Cd options FPU_CONTEXT 2607Make 2608.Em options COMPAT_SVR4 2609getcontext and setcontext include floating point registers. 2610.It Cd options MAGMA_DEBUG 2611Adds debugging messages to the 2612.Xr magma 4 2613device. 2614.It Cd options RASTERCONS_FULLSCREEN 2615Use the entire screen for the console. 2616.It Cd options RASTERCONS_SMALLFONT 2617Use the Fixed font on the console, instead of the normal font. 2618.It Cd options SUN4 2619Support sun4 class machines. 2620.It Cd options SUN4C 2621Support sun4c class machines. 2622.It Cd options SUN4M 2623Support sun4m class machines. 2624.It Cd options SUN4_MMU3L 2625.\" XXX ??? 2626Enable support for sun4 3-level MMU machines. 2627.It Cd options V9 2628Enable SPARC V9 assembler in 2629.Xr ddb 4 . 2630.El 2631.Ss sparc64-specific Options 2632.Bl -ohang 2633.It Cd options AUDIO_DEBUG 2634Enable simple event debugging of the logging of the 2635.Xr audio 4 2636device. 2637.It Cd options BLINK 2638Enable blinking of LED. 2639Blink rate is full cycle every N seconds for 2640N < then current load average. 2641See 2642.Xr getloadavg 3 . 2643.El 2644.Ss x68k-specific Options 2645.Bl -ohang 2646.It Cd options EXTENDED_MEMORY 2647Include support for extended memory, e.g., TS-6BE16 and 060turbo on-board. 2648.It Cd options JUPITER 2649Include support for Jupiter-X MPU accelerator 2650.It Cd options ZSCONSOLE,ZSCN_SPEED=value 2651Use the built-in serial port as the system-console. 2652Speed is specified in bps, defaults to 9600. 2653.It Cd options ITE_KERNEL_ATTR=value 2654Set the kernel message attribute for ITE. 2655Value, an integer, is a logical or of the following values: 2656.Bl -tag -width 4n -compact -offset indent 2657.It 1 2658color inversed 2659.It 2 2660underlined 2661.It 4 2662bolded 2663.El 2664.El 2665.Ss x86-specific Options 2666.Bl -ohang 2667.It Cd options NO_PCI_MSI_MSIX 2668Disable support for MSI/MSIX in the kernel. 2669See 2670.Xr pci_msi 9 2671for details of MSI/MSIX support 2672.It Cd options NO_PREEMPTION 2673Disables 2674.Xr kpreempt 9 2675support in the kernel. 2676.El 2677.\" The following requests should be uncommented and used where appropriate. 2678.\" .Sh FILES 2679.\" .Sh EXAMPLES 2680.Sh SEE ALSO 2681.Xr config 1 , 2682.Xr gcc 1 , 2683.Xr gdb 1 , 2684.Xr ktrace 1 , 2685.Xr quota 1 , 2686.Xr vndcompress 1 , 2687.Xr gettimeofday 2 , 2688.Xr i386_get_mtrr 2 , 2689.Xr i386_iopl 2 , 2690.Xr msgctl 2 , 2691.Xr msgget 2 , 2692.Xr msgrcv 2 , 2693.Xr msgsnd 2 , 2694.Xr ntp_adjtime 2 , 2695.Xr ntp_gettime 2 , 2696.Xr reboot 2 , 2697.Xr semctl 2 , 2698.Xr semget 2 , 2699.Xr semop 2 , 2700.Xr shmat 2 , 2701.Xr shmctl 2 , 2702.Xr shmdt 2 , 2703.Xr shmget 2 , 2704.Xr sysctl 3 , 2705.Xr apm 4 , 2706.Xr ddb 4 , 2707.Xr inet 4 , 2708.Xr md 4 , 2709.Xr pcibios 4 , 2710.Xr pcmcia 4 , 2711.Xr ppp 4 , 2712.Xr userconf 4 , 2713.Xr vnd 4 , 2714.Xr wscons 4 , 2715.Xr config 5 , 2716.Xr edquota 8 , 2717.Xr init 8 , 2718.Xr mdsetimage 8 , 2719.Xr mount_cd9660 8 , 2720.Xr mount_fdesc 8 , 2721.Xr mount_kernfs 8 , 2722.Xr mount_lfs 8 , 2723.Xr mount_mfs 8 , 2724.Xr mount_msdos 8 , 2725.Xr mount_nfs 8 , 2726.Xr mount_ntfs 8 , 2727.Xr mount_null 8 , 2728.Xr mount_portal 8 , 2729.Xr mount_procfs 8 , 2730.Xr mount_udf 8 , 2731.Xr mount_umap 8 , 2732.Xr mount_union 8 , 2733.Xr mrouted 8 , 2734.Xr newfs_lfs 8 , 2735.Xr ntpd 8 , 2736.Xr quotaon 8 , 2737.Xr rpc.rquotad 8 , 2738.Xr sysctl 8 , 2739.Xr in_getifa 9 , 2740.Xr kernhist 9 2741.Sh HISTORY 2742The 2743.Nm 2744man page first appeared in 2745.Nx 1.3 . 2746