.\"	$NetBSD: options.4,v 1.506.2.2 2021/10/25 15:47:50 martin Exp $
.\"
.\" Copyright (c) 1996
.\" 	Perry E. Metzger.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgment:
.\"	This product includes software developed for the NetBSD Project
.\"	by Perry E. Metzger.
.\" 4. The name of the author may not be used to endorse or promote products
.\"    derived from this software without specific prior written permission.
.\"
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
.Dd August 20, 2019
.Dt OPTIONS 4
.Os
.Sh NAME
.Nm options
.Nd Miscellaneous kernel configuration options
.Sh SYNOPSIS
.Cd cinclude ...
.Cd config ...
.Cd [no] file-system ...
.Cd ident ...
.Cd include ...
.Cd [no] makeoptions ...
.Cd maxusers ...
.Cd [no] options ...
.Cd [no] pseudo-device ...
.Sh DESCRIPTION
This manual page describes a number of miscellaneous kernel
configuration options that may be specified in a kernel config
file.
See
.Xr config 1
and
.Xr config 5
for information on how to configure and build kernels.
.Pp
The
.Ar no
form removes a previously specified option.
.Ss Keywords
The following keywords are recognized in a kernel configuration file:
.Bl -ohang
.It Sy cinclude Qq Ar filename
Conditionally includes another kernel configuration file whose name is
.Ar filename ,
which may be double-quoted and may be an explicit path or relative to
the kernel source directory.
Failure to open the named file is ignored.
.It Sy config Ar exec_name No root on Ar rootdev Oo type Ar fstype Oc \
Oo dumps on Ar dumpdev Oc
Defines a configuration whose kernel executable is named
.Ar exec_name ,
normally
.Dq netbsd ,
with its root file system of type
.Ar fstype
on the device
.Ar rootdev ,
and optionally specifying the location of kernel core dumps on the device
.Ar dumpdev .
.Ar dev
or
.Ar dumpdev
and
.Ar fstype
may be specified as
.Dq \&? ,
which is a wild card.
The root
.Ar fstype
and
.Ar dumpdev
are optional and assumed to be wild carded if they are not specified.
.It Ar device_instance No at Ar attachment \
Oo Ar locators value Oo ... Oc Oc Oo flags Ar value Oc
Define an instance of the device driver
.Ar device_instance
that attaches to the bus or device named
.Ar attachment .
An
.Ar attachment
may require additional information on where the device can be found, such
as an address, channel, function, offset, and/or slot, referred to as
.Ar locators ,
whose
.Ar value
often may be a wild card,
.Dq \&? .
Some device drivers have one or more
.Ar flags
that can be adjusted to affect the way they operate.
.It Sy file-system Ar fs_name Op , Ar fs_name Op ...
Include support for the file-system
.Ar fs_name .
.It Sy ident Qq Ar string
Sets the kernel identification string to
.Ar string .
.It Sy include Qq Ar filename
Functions the same as
.Ar cinclude ,
except failure to open
.Ar filename
produces a fatal error.
.It Sy makeoptions Ar name=value
Defines a
.Xr make 1
macro
.Ar name
with the value
.Ar value
in the kernel Makefile.
.It Sy maxusers Ar integer
Set the maxusers variable in the kernel.
.It Sy no Ar keyword Ar name Op Ar arguments Op ...
For the
.Xr config 1
.Ar keywords
file-system, makeoptions, options, and pseudo-device,
.Ar no
removes the file-system, makeoption, options, or pseudo-device,
.Ar name .
This is useful when a kernel configuration file includes another which
has undesired options.
.Pp
For example, a local configuration file that wanted the kitchen sink, but
not COMPAT_09 or bridging, might be:
.Bd -literal -offset indent
include "arch/i386/conf/GENERIC"
no options COMPAT_09
no pseudo-device bridge
.Ed
.It Sy options Ar option_name Op , Ar option_name=value Op ...
Specifies (or sets) the option, or comma-separated list of options,
.Ar option_name .
Some options expect to be assigned a value, which may be an integer,
a double-quoted word, a bare word, or an empty string
.Pq Qq .
Note that those are eventually handled by the C compiler, so the rules
of that language apply.
.Pp
.Em Note :
Options that are not defined by device definition files are passed to
the compile process as
.Fl D
flags to the C compiler.
.It Sy pseudo-device Ar name Op Ar N
Includes support for the pseudo-device
.Ar name .
Some pseudo-devices can have multiple or
.Ar N
instances.
.El
.Ss Compatibility Options
Note that compatibility options for older
.Nx
releases includes support for newer releases as well.
This means that typically only one of these is necessary, with the
.Cd COMPAT_09
option enabling all
.Nx
compatibility.
This does not include the
.Cd COMPAT_43
or
.Cd COMPAT_44
options.
.Bl -ohang
.It Cd options COMPAT_09
Enable binary compatibility with
.Nx 0.9 .
This enables support for
16-bit user, group, and process IDs (following revisions support
32-bit identifiers).
It also allows the use of the deprecated
.Xr getdomainname 3 ,
.Xr setdomainname 3 ,
and
.Xr uname 3
syscalls.
This option also allows using numeric file system identifiers rather
than strings.
Post
.Nx 0.9
versions use string identifiers.
.It Cd options COMPAT_10
Enable binary compatibility with
.Nx 1.0 .
This option allows the use of the file system name of
.Dq ufs
as an alias for
.Dq ffs .
The name
.Dq ffs
should be used post 1.0 in
.Pa /etc/fstab
and other files.
It also adds old syscalls for the
.At V
shared memory interface.
This was changed post 1.0 to work on 64-bit architectures.
This option also enables
.Dq sgtty
compatibility, without which programs using the old interface produce
an
.Dq inappropriate ioctl
error, and
.Pa /dev/io
only works when this option is set in the kernel,
see
.Xr io 4
on ports that support it.
.It Cd options COMPAT_11
Enable binary compatibility with
.Nx 1.1 .
This allows binaries running on the i386 port to gain direct access to
the io ports by opening
.Pa /dev/io
read/write.
This functionality was replaced by
.Xr i386_iopl 2
post 1.1.
On the Atari port, the location of the disk label was moved after 1.1.
When the
.Em COMPAT_11
option is set, the kernel will read (pre) 1.1 style disk labels as a
last resort.
When a disk label is re-written, the old style label will be replaced
with a post 1.1 style label.
This also enables the
.Em EXEC_ELF_NOTELESS
option.
.It Cd options COMPAT_12
Enable binary compatibility with
.Nx 1.2 .
This allows the use of old syscalls for
.Fn reboot
and
.Fn swapon .
The syscall numbers were changed post 1.2 to add functionality to the
.Xr reboot 2
syscall, and the new
.Xr swapctl 2
interface was introduced.
This also enables the
.Em EXEC_ELF_NOTELESS
option.
.It Cd options COMPAT_13
Enable binary compatibility with
.Nx 1.3 .
This allows the use of old syscalls for
.Fn sigaltstack ,
and also enables the old
.Xr swapctl 2
command
.Dv SWAP_STATS
(now called
.Dv SWAP_OSTATS ) ,
which does not include the
.Fa se_path
member of
.Va struct swapent .
.It Cd options COMPAT_14
Enable binary compatibility with
.Nx 1.4 .
This allows some old
.Xr ioctl 2
on
.Xr wscons 4
to be performed, and allows the
.Dv NFSSVC_BIOD
mode of the
.Xr nfssvc 2
system call to be used for compatibility with the deprecated nfsiod program.
.It Cd options COMPAT_15
Enable binary compatibility with
.Nx 1.5 .
Since there were no API changes from
.Nx 1.5
and
.Nx 1.6 ,
this option does nothing.
.It Cd options COMPAT_16
Enable binary compatibility with
.Nx 1.6 .
This allows the use of old signal trampoline code which has been deprecated
with the addition of
.Xr siginfo 2 .
.It Cd options COMPAT_20
Enable binary compatibility with
.Nx 2.0 .
This allows the use of old syscalls for
.Fn statfs ,
.Fn fstatfs ,
.Fn getfsstat
and
.Fn fhstatfs ,
which have been deprecated with the addition of the
.Xr statvfs 2 ,
.Xr fstatvfs 2 ,
.Xr getvfsstat 2
and
.Xr fhstatvfs 2
system calls.
.It Cd options COMPAT_30
Enable binary compatibility with
.Nx 3.0 .
See
.Xr compat_30 8
for details about the changes made after the
.Nx 3.0
release.
.It Cd options COMPAT_40
Enable binary compatibility with
.Nx 4.0 .
This allows the use of old
.Xr ptrace 2
calls for the SH3 platform.
It also enables the old
.Xr mount 2
system call that did not include the data length parameter.
The power_event_t structure's pev_switch is filled in.
.It Cd options COMPAT_43
Enables compatibility with
.Bx 4.3 .
This adds an old syscall for
.Xr lseek 2 .
It also adds the ioctls for
.Dv TIOCGETP
and
.Dv TIOCSETP .
The return values for
.Xr getpid 2 ,
.Xr getgid 2 ,
and
.Xr getuid 2
syscalls are modified as well, to return the parent's PID and
UID as well as the current process's.
It also enables the deprecated
.Dv NTTYDISC
terminal line discipline.
It also provides backwards compatibility with
.Dq old
SIOC[GS]IF{ADDR,DSTADDR,BRDADDR,NETMASK} interface ioctls, including
binary compatibility with code written before the introduction of the
sa_len field in sockaddrs.
It also enables
support for some older pre
.Bx 4.4
socket calls.
.It Cd options COMPAT_50
Enable binary compatibility with
.Nx 5.0 .
This enables support for the old
.Ft time_t
and
.Ft dev_t
types as 32 bit, and all the associated kernel interface changes.
It also enables old
.Xr gpio 4
and
.Xr rnd 4
interfaces.
.It Cd options COMPAT_60
Enable binary compatibility with
.Nx 6.0 .
This provides old
.Xr ccd 4
interfaces, enables support for old
.Xr cpuctl 8
microcode interfaces, and support for the old
.Ft ptmget
structure.
.It Cd options COMPAT_70
Enable binary compatibility with
.Nx 7.0 .
This provides support for old
.Xr route 4
interfaces.
.It Cd options COMPAT_BSDPTY
This option is currently on by default and enables the pty multiplexer
.Xr ptm 4
and
.Xr ptmx 4
to find and use ptys named
.Pa /dev/ptyXX
(master) and
.Pa /dev/ttyXX
(slave).
Eventually this option will become optional as ptyfs based pseudo-ttys become
the default, see
.Xr mount_ptyfs 8 .
.It Cd options COMPAT_LINUX
On those architectures that support it, this enables binary
compatibility with Linux ELF and
.Xr a.out 5
applications built for the same architecture.
This currently includes the alpha, arm, i386, m68k, mips, powerpc and
x86_64 ports.
.It Cd options COMPAT_LINUX32
On those 64 bit architectures that support it, this enables binary
compatibility with 32 bit Linux binaries.
For now this is limited to running i386 ELF Linux binaries on amd64.
.It Cd options COMPAT_SUNOS
On those architectures that support it, this enables binary
compatibility with SunOS 4.1 applications built for the same architecture.
This currently includes the sparc, sparc64 and most or all m68k ports.
Note that the sparc64 requires the
.Em COMPAT_NETBSD32
option for 64-bit kernels, in addition to this option.
.It Cd options COMPAT_ULTRIX
On those architectures that support it, this enables binary
compatibility with ULTRIX applications built for the same architecture.
This currently is limited to the pmax.
The functionality of this option is unknown.
.It Cd options COMPAT_FREEBSD
On those architectures that support it, this enables binary
compatibility with
.Fx
applications built for the same architecture.
At the moment this is limited to the i386 port.
.It Cd options COMPAT_NOMID
Enable compatibility with
.Xr a.out 5
executables that lack a machine ID.
This includes
.Nx 0.8 Ns 's
ZMAGIC format, and 386BSD and BSDI's
QMAGIC, NMAGIC, and OMAGIC
.Xr a.out 5
formats.
.It Cd options COMPAT_NETBSD32
On those architectures that support it, this enables binary
compatibility with 32-bit applications built for the same architecture.
This is currently limited to the amd64 and sparc64 ports, and only
applicable for 64-bit kernels.
.It Cd options COMPAT_AOUT_M68K
On m68k architectures which have switched to ELF,
this enables binary compatibility with
.Nx Ns /m68k
.Xr a.out 5
executables on
.Nx Ns /m68k
ELF kernels.
This handles alignment incompatibility of m68k ABI between
a.out and ELF which causes the structure padding differences.
Currently only some system calls which use
.Va struct stat
are adjusted and some binaries which use
.Xr sysctl 3
to retrieve network details would not work properly.
.It Cd options EMUL_NATIVEROOT=string
Just like emulated binaries first try looking up files in
an emulation root (e.g.
.Pa /emul/linux )
before looking them up in real root, this option causes native
binaries to first look up files in an "emulation" directory too.
This can be useful to test an amd64 kernel on top of an i386 system
before full migration: by unpacking the amd64 distribution in e.g.
.Pa /emul/netbsd64
and specifying that location as
.Cd EMUL_NATIVEROOT ,
native amd64 binaries can be run while the root file system remains
populated with i386 binaries.
Beware of
.Pa /dev
incompatibilities between i386 and amd64 if you do this.
.It Cd options EXEC_ELF_NOTELESS
Run unidentified ELF binaries as
.Nx
binaries.
This might be needed for very old
.Nx
ELF binaries on some archs.
These old binaries didn't contain an appropriate
.Li .note.netbsd.ident
section, and thus can't be identified by the kernel as
.Nx
binaries otherwise.
Beware - if this option is on, the kernel would run
.Em any
unknown ELF binaries as if they were
.Nx
binaries.
.El
.Ss Debugging Options
.Bl -ohang
.It Cd options DDB
Compiles in a kernel debugger for diagnosing kernel problems.
See
.Xr ddb 4
for details.
.Em NOTE :
not available on all architectures.
.It Cd options DDB_FROMCONSOLE=integer
If set to non-zero, DDB may be entered by sending a break on a serial
console or by a special key sequence on a graphics console.
A value of "0" ignores console breaks or key sequences.
If not explicitly specified, the default value is "1".
Note that this sets the value of the
.Em ddb.fromconsole
.Xr sysctl 3
variable which may be changed at run time \(em see
.Xr sysctl 8
for details.
.It Cd options DDB_HISTORY_SIZE=integer
If this is non-zero, enable history editing in the kernel debugger
and set the size of the history to this value.
.It Cd options DDB_ONPANIC
The default if not specified is
.Dq 1
- just enter into DDB.
If set to
.Dq 0
the kernel will attempt to print out a stack trace
and reboot the system.
If set to
.Dq -1
then neither a stack trace is printed or DDB entered -
it is as if DDB were not compiled into the kernel.
Note that this sets the value of the
.Em ddb.onpanic
.Xr sysctl 3
variable which may be changed at run time \(em see
.Xr sysctl 8
for details.
.It Cd options DDB_COMMANDONENTER=string
This option specify commands which will be executed on each entry to DDB.
This sets the default value of the
.Em ddb.commandonenter
.Xr sysctl 3
variable which may be changed at run time.
.It Cd options DDB_BREAK_CHAR=integer
This option overrides using break to enter the kernel debugger
on the serial console.
The value given is the ASCII value to be used instead.
This is currently only supported by the com driver.
.It Cd options DDB_VERBOSE_HELP
This option adds more verbose descriptions to the
.Em help
command.
.It Cd options DDB_PANICSTACKFRAMES=integer
Number of stack frames to display on panic.
Useful to avoid scrolling away the interesting frames on a glass tty.
Default value is
.Dv 65535
(all frames), useful value around
.Dv 10 .
.It Cd options KGDB
Compiles in a remote kernel debugger stub for diagnosing kernel problems
using the
.Dq remote target
feature of gdb.
See
.Xr gdb 1
for details.
.Em NOTE :
not available on all architectures.
.It Cd options KGDB_DEV
Device number
.Po
as a
.Dv dev_t
.Pc
of kgdb device.
.It Cd options KGDB_DEVADDR
Memory address of kgdb device.
.It Cd options KGDB_DEVMODE
Permissions of kgdb device.
.It Cd options KGDB_DEVNAME
Device name of kgdb device.
.It Cd options KGDB_DEVRATE
Baud rate of kgdb device.
.It Cd makeoptions DEBUG="-g"
The
.Fl g
flag causes
.Pa netbsd.gdb
to be built in addition to
.Pa netbsd .
.Pa netbsd.gdb
is useful for debugging kernel crash dumps with gdb.
See
.Xr gdb 1
for details.
.It Cd options DEBUG
Turns on miscellaneous kernel debugging.
Since options are turned into preprocessor defines (see above),
.Em options DEBUG
is equivalent to doing a
.Em #define DEBUG
throughout the kernel.
Much of the kernel has
.Em #ifdef DEBUG
conditionalized debugging code.
Note that many parts of the kernel (typically device drivers) include their own
.Em #ifdef XXX_DEBUG
conditionals instead.
This option also turns on certain other options,
which may decrease system performance.
Systems with this option are not suitable for regular use, and are
intended only for debugging or looking for bugs.
.It Cd options DIAGNOSTIC
Adds code to the kernel that does internal consistency checks.
This code will cause the kernel to panic if corruption of internal data
structures is detected.
Historically, the performance degradation is sufficiently small that
it is reasonable for systems with
.Em options DIAGNOSTIC
to be in production use, with the real consideration not being
performance but instead a preference for more panics versus continued
operation with undetected problems.
.It Cd options LOCKDEBUG
Adds code to the kernel to detect incorrect use of locking primitives
(mutex, rwlock).
This code will cause the kernel to check for dead lock conditions.
It will also check for memory being freed to not contain initialised
lock primitives.
Functions for use in
.Xr ddb 4
to check lock chains etc. are also enabled.
These checks are very expensive and can decrease performance on
multi-processor machines by a factor of three.
.It Cd options KDTRACE_HOOKS
Adds hooks for the DTrace tracing facility, which allows users to
analyze many aspects of system and application behavior.
See
.Xr dtrace 1
for details.
.It Cd options KSTACK_CHECK_MAGIC
Check kernel stack usage and panic if stack overflow is detected.
This check is performance sensitive because it scans stack on each context
switch.
.It Cd options KTRACE
Add hooks for the system call tracing facility, which allows users to
watch the system call invocation behavior of processes.
See
.Xr ktrace 1
for details.
.It Cd options MSGBUFSIZE=integer
This option sets the size of the kernel message buffer.
This buffer holds the kernel output of
.Fn printf
when not (yet) read by
.Xr syslogd 8 .
This is particularly useful when the system has crashed and you wish to lookup
the kernel output from just before the crash.
Also, since the autoconfig output becomes more and more verbose,
it sometimes happens that the message buffer overflows before
.Xr syslogd 8
was able to read it.
Note that not all systems are capable of obtaining a variable sized message
buffer.
There are also some systems on which memory contents are not preserved
across reboots.
.It Cd options KERNHIST
Enables the kernel history logs, which create in-memory traces of
various kernel activities.
These logs can be displayed by using
.Cm show kernhist
from DDB.
See the kernel source file
.Pa sys/kern/kern_history.c
and the
.Xr kernhist 9
manual for details.
.It Cd options KERNHIST_PRINT
Prints the kernel history logs on the system console as entries are added.
Note that the output is
.Em extremely
voluminous, so this option is really only useful for debugging
the very earliest parts of kernel initialization.
.It Cd options UVMHIST
Like
.Em KERNHIST ,
it enables the UVM history logs.
These logs can be displayed by using
.Cm show kernhist
from DDB.
See the kernel source file
.Pa sys/uvm/uvm_stat.c
for details.
.It Cd options UVMHIST_PRINT
Like
.Em UVMHIST ,
it prints the UVM history logs on the system console as entries are added.
Note that the output is
.Em extremely
voluminous, so this option is really only useful for debugging
the very earliest parts of kernel initialization.
.It Cd options UVMHIST_MAPHIST_SIZE
Set the size of the
.Dq maphist
kernel history.
The default is 100.
This option depends upon the
.Em UVMHIST
option.
.It Cd options UVMHIST_PDHIST_SIZE
Set the size of the
.Dq pdhist
kernel history.
The default is 100.
This option depends upon the
.Em UVMHIST
option.
.It Cd options BIOHIST
Like
.Em KERNHIST ,
it enables the BIO history logs.
These logs can be displayed by using
.Cm show kernhist
from DDB, and can help in debugging problems with Buffered I/O operations.
See the kernel source file
.Pa sys/kern/vfs_vio.c
for details.
.It Cd options BIOHIST_PRINT
Like
.Em BIOHIST ,
it prints the BIO history logs on the system console as entries are added.
Note that the output is
.Em extremely
voluminous, so this option is really only useful for debugging
the very earliest parts of kernel initialization.
.It Cd options BIOHIST_SIZE
Set the size of the
.Dq biohist
kernel history.
The default is 500.
This option depends upon the
.Em BIOHIST
option.
.El
.Ss File Systems
.Bl -ohang
.It Cd file-system FFS
Includes code implementing the Berkeley Fast File System
.Po Em FFS Pc .
Most machines need this if they are not running diskless.
.It Cd file-system EXT2FS
Includes code implementing the Second Extended File System
.Po Em ext2 Pc ,
revision 0 and revision 1 with the
.Em filetype ,
.Em sparse_super
and
.Em large_file
options.
This is the most commonly used file system on the Linux operating system,
and is provided here for compatibility.
Some of the specific features of
.Em ext2
like the "behavior on errors" are not implemented.
See
.Xr mount_ext2fs 8
for details.
.It Cd file-system LFS
.Bq Em EXPERIMENTAL
Include the Log-structured File System
.Po Em LFS Pc .
See
.Xr mount_lfs 8
and
.Xr newfs_lfs 8
for details.
.It Cd file-system MFS
Include the Memory File System
.Po Em MFS Pc .
This file system stores files in swappable memory, and produces
notable performance improvements when it is used as the file store
for
.Pa /tmp
and similar file systems.
See
.Xr mount_mfs 8
for details.
.It Cd file-system NFS
Include the client side of the Network File System (NFS)
remote file sharing protocol.
Although the bulk of the code implementing NFS
is kernel based, several user level daemons are needed for it to work.
See
.Xr mount_nfs 8
for details.
.It Cd file-system CD9660
Includes code for the ISO 9660 + Rock Ridge file system, which is
the standard file system on many CD-ROM discs.
Useful primarily if you have a CD-ROM drive.
See
.Xr mount_cd9660 8
for details.
.It Cd file-system MSDOSFS
Includes the MS-DOS FAT file system, which is reportedly still used
by unfortunate people who have not heard about
.Nx .
Also implements the Windows 95 extensions to the same, which permit
the use of longer, mixed case file names.
See
.Xr mount_msdos 8
and
.Xr fsck_msdos 8
for details.
.It Cd file-system NTFS
.Bq Em EXPERIMENTAL
Includes code for the Microsoft Windows NT file system.
See
.Xr mount_ntfs 8
for details.
.It Cd file-system FDESC
Includes code for a file system, conventionally mounted on
.Pa /dev/fd ,
which permits access to the per-process file descriptor space via
special files in the file system.
See
.Xr mount_fdesc 8
for details.
Note that this facility is redundant, and thus unneeded on most
.Nx
systems, since the
.Xr fd 4
pseudo-device driver already provides identical functionality.
On most
.Nx
systems, instances of
.Xr fd 4
are mknoded under
.Pa /dev/fd/
and on
.Pa /dev/stdin ,
.Pa /dev/stdout ,
and
.Pa /dev/stderr .
.It Cd file-system KERNFS
Includes code which permits the mounting of a special file system
(normally mounted on
.Pa /kern )
in which files representing various kernel variables and parameters
may be found.
See
.Xr mount_kernfs 8
for details.
.It Cd file-system NULLFS
Includes code for a loopback file system.
This permits portions of the file hierarchy to be re-mounted in other places.
The code really exists to provide an example of a stackable file system layer.
See
.Xr mount_null 8
for details.
.It Cd file-system OVERLAY
Includes code for a file system filter.
This permits the overlay file system to intercept all access to an underlying
file system.
This file system is intended to serve as an example of a stacking file
system which has a need to interpose itself between an underlying file
system and all other access.
See
.Xr mount_overlay 8
for details.
.It Cd file-system PROCFS
Includes code for a special file system (conventionally mounted on
.Pa /proc )
in which the process space becomes visible in the file system.
Among
other things, the memory spaces of processes running on the system are
visible as files, and signals may be sent to processes by writing to
.Pa ctl
files in the procfs namespace.
See
.Xr mount_procfs 8
for details.
.It Cd file-system UDF
.Bq Em EXPERIMENTAL
Includes code for the UDF file system commonly found on CD and DVD
media but also on USB sticks.
Currently supports read and write access upto UDF 2.01 and somewhat limited
write support for UDF 2.50.
It is marked experimental since there is no
.Xr fsck_udf 8 .
See
.Xr mount_udf 8
for details.
.It Cd file-system UMAPFS
Includes a loopback file system in which user and group IDs may be
remapped \(em this can be useful when mounting alien file systems with
different UIDs and GIDs than the local system.
See
.Xr mount_umap 8
for details.
.It Cd file-system UNION
.Bq Em EXPERIMENTAL
Includes code for the union file system, which permits directories to
be mounted on top of each other in such a way that both file systems
remain visible \(em this permits tricks like allowing writing (and the
deleting of files) on a read-only file system like a CD-ROM by
mounting a local writable file system on top of the read-only file
system.
See
.Xr mount_union 8
for details.
.It Cd file-system CODA
.Bq Em EXPERIMENTAL
Includes code for the Coda file system.
Coda is a distributed file system like NFS and AFS.
It is freely available, like NFS, but it functions much like AFS in being a
.Dq stateful
file system.
Both Coda and AFS cache files on your local machine to improve performance.
Then Coda goes a step further than AFS by letting you access the cached
files when there is no available network, viz. disconnected laptops and
network outages.
In Coda, both the client and server are outside the kernel which makes
them easier to experiment with.
Coda is available for several UNIX and non-UNIX platforms.
See
.Lk http://www.coda.cs.cmu.edu
for more details.
.Em NOTE :
You also need to enable the pseudo-device, vcoda, for the Coda
file system to work.
.It Cd file-system SMBFS
.Bq Em EXPERIMENTAL
Includes code for the SMB/CIFS file system.
See
.Xr mount_smbfs 8
for details.
.Em NOTE :
You also need to enable the pseudo-device, nsmb, for the SMB
file system to work.
.It Cd file-system PTYFS
Includes code for a special file system (normally mounted on
.Pa /dev/pts )
in which pseudo-terminal slave devices become visible in the file system.
See
.Xr mount_ptyfs 8
for details.
.It Cd file-system TMPFS
Includes code for the efficient memory file system, normally used over
.Pa /tmp .
See
.Xr mount_tmpfs 8
for details.
.It Cd file-system PUFFS
Includes kernel support for the pass-to-userspace framework file system.
It can be used to implement file system functionality in userspace.
See
.Xr puffs 3
for more details.
This enables for example sshfs:
.Xr mount_psshfs 8 .
.El
.Ss File System Options
.Bl -ohang
.It Cd options DISKLABEL_EI
Enable
.Dq Endian-Independent
.Xr disklabel 5
support.
This allows a system to recognize a disklabel written in the other byte order.
For writing, when a label already exists, its byte order is preserved.
Otherwise, a new label is written in the native byte order.
To specify the byte order explicitly, the
.Fl F
option of
.Xr disklabel 8
should be used with the
.Fl B
option in order to avoid using
.Xr ioctl 2 ,
which results in the default behavior explained above.
At the moment this option is restricted to the following ports:
amd64, bebox, emips, epoc32, evbarm, i386, ibmnws, landisk, mvmeppc, prep,
.\" riscv,
rs6000, sandpoint,
.\" usermode,
xen, and zaurus;
also to machines of the
evbmips and evbppc ports that support
Master Boot Record (MBR).
.It Cd options MAGICLINKS
Enables the expansion of special strings
.Po
beginning with
.Dq @
.Pc
when traversing symbolic links.
See
.Xr symlink 7
for a list of supported strings.
Note that this option only controls the enabling of this feature
by the kernel at boot-up.
This feature can still be manipulated with the
.Xr sysctl 8
command regardless of the setting of this option.
.It Cd options NFSSERVER
Include the server side of the
.Em NFS
(Network File System) remote file sharing protocol.
Although the bulk of the code implementing
.Em NFS
is kernel based, several user level daemons are needed for it to
work.
See
.Xr mountd 8
and
.Xr nfsd 8
for details.
.It Cd options NVNODE=integer
This option sets the size of the cache used by the name-to-inode translation
routines, (a.k.a. the
.Fn namei
cache, though called by many other names in the kernel source).
By default, this cache has
.Dv ( NPROC + NTEXT + 100 )
entries (NPROC set as 20 + 16 * MAXUSERS and NTEXT as 80 + NPROC / 8).
A reasonable way to derive a value of
.Dv NVNODE ,
should you notice a large number of namei cache misses with a tool such as
.Xr systat 1 ,
is to examine your system's current computed value with
.Xr sysctl 8 ,
(which calls this parameter "kern.maxvnodes") and to increase this value
until either the namei cache hit rate improves or it is determined that
your system does not benefit substantially from an increase in the size of
the namei cache.
.It Cd options NAMECACHE_ENTER_REVERSE
Causes the namei cache to always enter a reverse mapping (vnode -> name)
as well as a normal one.
Normally, this is already done for directory vnodes, to speed up the getcwd
operation.
This option will cause longer hash chains in the reverse cache, and thus
slow down getcwd somewhat.
However, it does make vnode -> path translations possible in some cases.
For now, only useful if strict
.Pa /proc/#/maps
emulation for Linux binaries is required.
.El
.Ss Options for FFS/UFS File Systems
.Bl -ohang
.It Cd options APPLE_UFS
Enable support for UFS file systems created on Mac OS X.
.It Cd options FFS_EI
Enable
.Dq Endian-Independent
FFS support.
This allows a system to mount an FFS file system created for another
architecture, at a small performance cost for all FFS file systems.
See also
.Xr newfs 8 ,
.Xr fsck_ffs 8 ,
.Xr dumpfs 8
for file system byte order status and manipulation.
.It Cd options FFS_NO_SNAPSHOT
Disable support for the creation of file system internal snapshot
of FFS file systems.
Maybe useful for install media kernels, small memory systems and
embedded systems which don't require the snapshot support.
.It Cd options QUOTA
Enables kernel support for traditional quotas in FFS.
Traditional quotas store the quota information in external files and
require
.Xr quotacheck 8
and
.Xr quotaon 8
at boot time.
Traditional quotas are limited to 32-bit sizes and are at this point
considered a legacy feature.
.It Cd options QUOTA2
Enables kernel support for in-volume quotas in FFS.
The quota information is file system metadata maintained by
.Xr fsck 8
and/or WAPBL journaling.
MFS volumes can also use
.Dv QUOTA2
quotas; see
.Xr mount_mfs 8
for more information.
.It Cd options UFS_DIRHASH
Increase lookup performance by maintaining in-core hash tables
for large directories.
.It Cd options UFS_EXTATTR
Enable extended attribute support for UFS1 file systems.
.It Cd options WAPBL
Enable
.Dq Write Ahead Physical Block Logging file system journaling .
This provides rapid file system consistency checking after a system outage.
It also provides better general use performance over regular FFS.
See also
.Xr wapbl 4 .
.El
.Ss Options for the LFS File System
.Bl -ohang
.\" .It Cd options LFS_KERNEL_RFW
.\" There is no documentation for this. (XXX)
.\" .It Cd options LFS_QUOTA
.\" Enable traditional quota support for LFS.
.\" (It is not clear if this works.)
.\" .It Cd options LFS_QUOTA2
.\" Enable modernized 64-bit quota support for LFS.
.\" (This does not work yet.)
.It Cd options LFS_EI
Enable
.Dq Endian-Independent
LFS support.
This allows (at a small performance cost) mounting an LFS file system
created for another architecture.
.\" .It Cd options LFS_EXTATTR
.\" Enable extended attribute support for LFS.
.\" (It is not clear if this works.)
.It Cd options LFS_DIRHASH
Increase lookup performance by maintaining in-core hash tables
for large directories.
.El
.Ss Options for the ext2fs File System
.Bl -ohang
.It Cd options EXT2FS_SYSTEM_FLAGS
This option changes the behavior of the APPEND and IMMUTABLE flags
for a file on an
.Em ext2
file system.
Without this option, the superuser or owner of the file can
set and clear them.
With this option, only the superuser can set them, and
they can't be cleared if the securelevel is greater than 0.
See also
.Xr chflags 1
and
.Xr secmodel_securelevel 9 .
.El
.Ss Options for the NFS File System
.Bl -ohang
.It Cd options NFS_BOOT_BOOTP
Enable use of the BOOTP protocol (RFCs 951 and 1048) to get configuration
information if NFS is used to mount the root file system.
See
.Xr diskless 8
for details.
.It Cd options NFS_BOOT_BOOTSTATIC
Enable use of static values defined as
.Dq NFS_BOOTSTATIC_MYIP ,
.Dq NFS_BOOTSTATIC_GWIP ,
.Dq NFS_BOOTSTATIC_SERVADDR ,
and
.Dq NFS_BOOTSTATIC_SERVER
in kernel options to get configuration information
if NFS is used to mount the root file system.
.It Cd options NFS_BOOT_DHCP
Same as
.Dq NFS_BOOT_BOOTP ,
but use the DHCP extensions to the
BOOTP protocol (RFC 1541).
.It Cd options NFS_BOOT_BOOTP_REQFILE
Specifies the string sent in the bp_file field of the BOOTP/DHCP
request packet.
.It Cd options NFS_BOOT_BOOTPARAM
Enable use of the BOOTPARAM protocol, consisting of RARP and
BOOTPARAM RPC, to get configuration information if NFS
is used to mount the root file system.
See
.Xr diskless 8
for details.
.It Cd options NFS_BOOT_RWSIZE=value
Set the initial NFS read and write sizes for diskless-boot requests.
The normal default is 8Kbytes.
This option provides a way to lower the value (e.g., to 1024 bytes)
as a workaround for buggy network interface cards or boot PROMs.
Once booted, the read and write request sizes can be increased by
remounting the file system.
See
.Xr mount_nfs 8
for details.
.It Cd options NFS_V2_ONLY
Reduce the size of the NFS client code by omitting code that's only required
for NFSv3 and NQNFS support, leaving only that code required to use NFSv2
servers.
.It Cd options NFS_BOOT_TCP
Use NFS over TCP instead of the default UDP, for mounting root.
.El
.Ss Buffer queue strategy options
The following options enable alternative buffer queue strategies.
.Bl -ohang
.It Cd options BUFQ_READPRIO
Enable alternate buffer queue strategy for disk I/O.
In the default strategy, outstanding disk requests are ordered by
sector number and sent to the disk, regardless of whether the
operation is a read or write; this option gives priority to issuing
read requests over write requests.
Although requests may therefore be issued out of sector-order, causing
more seeks and thus lower overall throughput, interactive system
responsiveness under heavy disk I/O load may be improved, as processes
blocking on disk reads are serviced sooner (file writes typically
don't cause applications to block).
The performance effect varies greatly depending on the hardware, drive
firmware, file system configuration, workload, and desired performance
trade-off.
Systems using drive write-cache (most modern IDE disks, by default)
are unlikely to benefit and may well suffer; such disks acknowledge
writes very quickly, and optimize them internally according to
physical layout.
Giving these disks as many requests to work with as possible (the
standard strategy) will typically produce the best results, especially
if the drive has a large cache; the drive will silently complete
writes from cache as it seeks for reads.
Disks that support a large number of concurrent tagged requests (SCSI
disks and many hardware RAID controllers) expose this internal
scheduling with tagged responses, and don't block for reads; such
disks may not see a noticeable difference with either strategy.
However, if IDE disks are run with write-cache disabled for safety,
writes are not acknowledged until actually completed, and only one
request can be outstanding; a large number of small writes in one
locality can keep the disk busy, starving reads elsewhere on the disk.
Such systems are likely to see the most benefit from this option.
Finally, the performance interaction of this option with ffs soft
dependencies can be subtle, as that mechanism can drastically alter
the workload for file system metadata writes.
.It Cd options BUFQ_PRIOCSCAN
Enable another buffer queue strategy for disk I/O, per-priority cyclical scan.
.It Cd options NEW_BUFQ_STRATEGY
Synonym of
.Em BUFQ_READPRIO .
.El
.Ss Miscellaneous Options
.Bl -ohang
.It Cd options CPU_UCODE
Support cpu microcode loading via
.Xr cpuctl 8 .
.It Cd options MEMORY_DISK_DYNAMIC
This option makes the
.Xr md 4
RAM disk size dynamically sized.
It is incompatible with
.Xr mdsetimage 8 .
.It Cd options MEMORY_DISK_HOOKS
This option allows for some machine dependent functions to be called when
the
.Xr md 4
RAM disk driver is configured.
This can result in automatically loading a RAM disk from floppy on
open (among other things).
.It Cd options MEMORY_DISK_IS_ROOT
Forces the
.Xr md 4
RAM disk to be the root device.
This can only be overridden when
the kernel is booted in the 'ask-for-root' mode.
.It Cd options MEMORY_DISK_ROOT_SIZE=integer
Allocates the given number of 512 byte blocks as memory for the
.Xr md 4
RAM disk, to be populated with
.Xr mdsetimage 8 .
.It Cd options MEMORY_DISK_SERVER=0
Do not include the interface to a userland memory disk server process.
Per default, this option is set to 1, including the support code.
Useful for install media kernels.
.It Cd options MEMORY_DISK_RBFLAGS=value
This option sets the
.Xr reboot 2
flags used when booting with a memory disk as root file system.
Possible values include
.Dv RB_AUTOBOOT
(boot in the usual fashion - default value), and
.Dv RB_SINGLE
(boot in single-user mode).
.It Cd options MODULAR
Enables the framework for kernel modules (see
.Xr module 7 ) .
.It Cd options MODULAR_DEFAULT_AUTOLOAD
Enables the autoloading of kernel modules by default.
This sets the default value of the
.Em kern.module.autoload
.Xr sysctl 3
variable which may be changed at run time.
.It Cd options VND_COMPRESSION
Enables the
.Xr vnd 4
driver to also handle compressed images.
See
.Xr vndcompress 1 ,
.Xr vnd 4
and
.Xr vnconfig 8
for more information.
.It Cd options SPLDEBUG
Help the kernel programmer find bugs related to the interrupt priority
level.
When
.Fn spllower
or
.Fn splraise
changes the current CPU's interrupt priority level to or from
.Dv IPL_HIGH ,
record a backtrace.
Read
.Xr i386/return_address 9
for caveats about collecting backtraces.
This feature is experimental, and it is only available on i386.
See
.Pa sys/kern/subr_spldebug.c .
.It Cd options TFTPROOT
Download the root memory disk through TFTP at root mount time.
This enables the use of a root RAM disk without requiring it to be
embedded in the kernel using
.Xr mdsetimage 8 .
The RAM disk name is obtained using DHCP's filename parameter.
This option requires
.Em MEMORY_DISK_HOOKS ,
.Em MEMORY_DISK_DYNAMIC ,
and
.Em MEMORY_DISK_IS_ROOT .
It is incompatible with
.Em MEMORY_DISK_ROOT_SIZE .
.It Cd options HZ=integer
On ports that support it, set the system clock frequency (see
.Xr hz 9 )
to the supplied value.
Handle with care.
.It Cd options NTP
Turns on in-kernel precision timekeeping support used by software
implementing
.Em NTP
(Network Time Protocol, RFC 1305).
The
.Em NTP
option adds an in-kernel Phase-Locked Loop (PLL) for normal
.Em NTP
operation, and a Frequency-Locked Loop (FLL) for intermittently-connected
operation.
.Xr ntpd 8
will employ a user-level PLL when kernel support is unavailable,
but the in-kernel version has lower latency and more precision, and
so typically keeps much better time.
.Pp
The interface to the kernel
.Em NTP
support is provided by the
.Xr ntp_adjtime 2
and
.Xr ntp_gettime 2
system calls, which are intended for use by
.Xr ntpd 8
and are enabled by the option.
On systems with sub-microsecond resolution timers, or where (HZ/100000)
is not an integer, the
.Em NTP
option also enables extended-precision arithmetic to keep track of
fractional clock ticks at NTP time-format precision.
.It Cd options PPS_SYNC
This option enables a kernel serial line discipline for receiving time
phase signals from an external reference clock such as a radio clock.
.Po
The
.Em NTP
option (which see) must be on if the
.Em PPS_SYNC
option is used
.Pc .
Some reference clocks generate a Pulse Per Second (PPS) signal in
phase with their time source.
The
.Em PPS
line discipline receives this signal on either the data leads
or the DCD control lead of a serial port.
.Pp
.Em NTP
uses the PPS signal to discipline the local clock oscillator to a high
degree of precision (typically less than 50 microseconds in time and
0.1 ppm in accuracy).
.Em PPS
can also generate a serial output pulse when the system receives a PPS
interrupt.
This can be used to measure the system interrupt latency and thus calibrate
.Em NTP
to account for it.
Using
.Em PPS
usually requires a gadget box
to convert from TTL to RS-232 signal levels.
The gadget box and PPS are described in more detail in the HTML documentation
for
.Xr ntpd 8
in
.Pa /usr/share/doc/html/ntp .
.Pp
.Nx
currently supports this option in
.Xr com 4
and
.Xr zsc 4 .
.It Cd options SETUIDSCRIPTS
Allows scripts with the setuid bit set to execute as the effective
user rather than the real user, just like binary executables.
.Pp
.Em NOTE :
Using this option will also enable
.Em options FDSCRIPTS
.It Cd options FDSCRIPTS
Allows execution of scripts with the execute bit set, but not the
read bit, by opening the file and passing the file descriptor to
the shell, rather than the filename.
.Pp
.Em NOTE :
Execute only (non-readable) scripts will have
.Va argv[0]
set to
.Pa /dev/fd/* .
What this option allows as far as security is
concerned, is the ability to safely ensure that the correct script
is run by the interpreter, as it is passed as an already open file.
.It Cd options RTC_OFFSET=integer
The kernel (and typically the hardware battery backed-up clock on
those machines that have one) keeps time in
.Em UTC
(Universal Coordinated Time, once known as
.Em GMT ,
or Greenwich Mean Time)
and not in the time of the local time zone.
The
.Em RTC_OFFSET
option is used on some ports (such as the i386) to tell the kernel
that the hardware clock is offset from
.Em UTC
by the specified number of minutes.
This is typically used when a machine boots several operating
systems and one of them wants the hardware clock to run in the
local time zone and not in
.Em UTC ,
e.g.
.Em RTC_OFFSET=300
means
the hardware clock is set to US Eastern Time (300 minutes behind
.Em UTC ) ,
and not
.Em UTC .
(Note:
.Em RTC_OFFSET
is used to initialize a kernel variable named
.Va rtc_offset
which is the source actually used to determine the clock offset, and
which may be accessed via the kern.rtc_offset sysctl variable.
See
.Xr sysctl 8
and
.Xr sysctl 3
for details.
Since the kernel clock is initialized from the hardware clock very
early in the boot process, it is not possible to meaningfully change
.Va rtc_offset
in system initialization scripts.
Changing this value currently may only be done at kernel compile
time or by patching the kernel and rebooting).
.Pp
.Em NOTE :
Unfortunately, in many cases where the hardware clock
is kept in local time, it is adjusted for Daylight Savings
Time; this means that attempting to use
.Em RTC_OFFSET
to let
.Nx
coexist with such an operating system, like Windows,
would necessitate changing
.Em RTC_OFFSET
twice a year.
As such, this solution is imperfect.
.It Cd options MAXUPRC=integer
Sets the soft
.Dv RLIMIT_NPROC
resource limit, which specifies the maximum number of simultaneous
processes a user is permitted to run, for process 0;
this value is inherited by its child processes.
It defaults to
.Em CHILD_MAX ,
which is currently defined to be 160.
Setting
.Em MAXUPRC
to a value less than
.Em CHILD_MAX
is not permitted, as this would result in a violation of the semantics of
.St -p1003.1-90 .
.It Cd options NOFILE=integer
Sets the soft
.Dv RLIMIT_NOFILE
resource limit, which specifies the maximum number of open
file descriptors for each process;
this value is inherited by its child processes.
It defaults to
.Em OPEN_MAX ,
which is currently defined to be 128.
.It Cd options MAXFILES=integer
Sets the default value of the
.Em kern.maxfiles
sysctl variable, which indicates the maximum number of files that may
be open in the system.
.It Cd options DEFCORENAME=string
Sets the default value of the
.Em kern.defcorename
sysctl variable, otherwise it is set to
.Nm %n.core .
See
.Xr sysctl 8
and
.Xr sysctl 3
for details.
.It Cd options RASOPS_CLIPPING
Enables clipping within the
.Nm rasops
raster-console output system.
.Em NOTE :
only available on architectures that use
.Nm rasops
for console output.
.It Cd options RASOPS_SMALL
Removes optimized character writing code from the
.Nm rasops
raster-console output system.
.Em NOTE :
only available on architectures that use
.Nm rasops
for console output.
.It Cd options INCLUDE_CONFIG_FILE
Embeds the kernel config file used to define the kernel in the kernel
binary itself.
The embedded data also includes any files directly included by the config
file itself, e.g.
.Pa GENERIC.local
or
.Pa std.$MACHINE .
The embedded config file can be extracted from the resulting kernel with
.Xr config 1
.Fl x ,
or by the following command:
.Bd -literal -offset indent
strings netbsd | sed -n 's/^_CFG_//p' | unvis
.Ed
.It Cd options INCLUDE_JUST_CONFIG
Similar to the above option, but includes just the actual config file,
not any included files.
.It Cd options PIPE_SOCKETPAIR
Use slower, but smaller socketpair(2)-based pipe implementation instead
of default faster, but bigger one.
Primarily useful for installation kernels.
.It Cd options USERCONF
Compiles in the in-kernel device configuration manager.
See
.Xr userconf 4
for details.
.It Cd options SCDEBUG_DEFAULT
Used with the
.Cd options SYSCALL_DEBUG
described below to choose which types of events are displayed.
.Pp
.Bl -tag -width "SCDEBUG_KERNHIST" -compact -offset indent
.It Dv SCDEBUG_CALLS
Show system call entry points.
.It Dv SCDEBUG_RETURNS
Show system call exit points.
.It Dv SCDEBUG_ALL
Show all system call requestes, including unimplemented calls.
.It Dv SCDEBUG_SHOWARGS
Show the arguments provided.
.It Dv SCDEBUG_KERNHIST
Store a restricted form of the system call debug in a kernel history
instead of printing it to the console.
This option relies upon
.Cd options KERNHIST .
.El
.Pp
The default value is
.Dv (SCDEBUG_CALLS|SCDEBUG_RETURNS|SCDEBUG_SHOWARGS) .
.It Cd options SYSCALL_DEBUG
Useful for debugging system call issues, usually in early single user bringup.
By default, writes entries to the system console for most system call events.
Can be configured with the
.Cd options SCDEBUG_DEFAULT
option to to use the
.Cd options KERNHIST
facility instead.
.It Cd options SYSCALL_STATS
Count the number of times each system call number is called.
The values can be read through the sysctl interface and displayed using
.Xr systat 1 .
.Em NOTE :
not yet available on all architectures.
.It Cd options SYSCALL_TIMES
Count the time spent (using
.Fn cpu_counter32 )
in each system call.
.Em NOTE :
Using this option will also enable
.Cd options SYSCALL_STATS .
.It Cd options SYSCALL_TIMES_HASCOUNTER
Force use of
.Fn cpu_counter32
even if
.Fn cpu_hascounter
reports false.
Useful for systems where the cycle counter doesn't run at a constant rate
(e.g. Soekris boxes).
.It Cd options XSERVER_DDB
A supplement to XSERVER that adds support for entering
.Xr ddb 4
while in X11.
.It Cd options FILEASSOC
Support for
.Xr fileassoc 9 .
Required for
.Cd options PAX_SEGVGUARD
and
.Cd pseudo-device veriexec .
.It Cd options FILEASSOC_NHOOKS=integer
Number of storage slots per file for
.Xr fileassoc 9 .
Default is 4.
.El
.Ss Networking Options
.Bl -ohang
.It Cd options GATEWAY
Enables
.Em IPFORWARDING
and (on most ports) increases the size of
.Em NMBCLUSTERS .
In general,
.Em GATEWAY
is used to indicate that a system should act as a router, and
.Em IPFORWARDING
is not invoked directly.
(Note that
.Em GATEWAY
has no impact on protocols other than IP).
.Em GATEWAY
option also compiles IPv4 and IPv6 fast forwarding code into the kernel.
.It Cd options IPFORWARDING=value
If
.Em value
is 1 this enables IP routing behavior.
If
.Em value
is 0 (the default), it disables it.
The
.Em GATEWAY
option sets this to 1 automatically.
With this option enabled, the machine will forward IP datagrams destined
for other machines between its interfaces.
Note that even without this option, the kernel will
still forward some packets (such as source routed packets) \(em removing
.Em GATEWAY
and
.Em IPFORWARDING
is insufficient to stop all routing through a bastion host on a
firewall \(em source routing is controlled independently.
Note that IP forwarding may be turned on and off independently of the
setting of the
.Em IPFORWARDING
option through the use of the
.Em net.inet.ip.forwarding
sysctl variable.
If
.Em net.inet.ip.forwarding
is 1, IP forwarding is on.
See
.Xr sysctl 8
and
.Xr sysctl 3
for details.
.It Cd options IFA_STATS
Tells the kernel to maintain per-address statistics on bytes sent
and received over (currently) Internet and AppleTalk addresses.
.\"This can be a fairly expensive operation, so you probably want to
.\"keep this disabled.
The option is not recommended as it degrades system stability.
.It Cd options IFQ_MAXLEN=value
Increases the allowed size of the network interface packet queues.
The default queue size is 50 packets, and you do not normally need
to increase it.
.It Cd options IPSELSRC
Includes support for source-address selection policies.
See
.Xr in_getifa 9 .
.It Cd options MROUTING
Includes support for IP multicast routers.
You certainly want
.Em INET
with this.
Multicast routing is controlled by the
.Xr mrouted 8
daemon.
See also option
.Cd PIM .
.It Cd options PIM
Includes support for Protocol Independent Multicast (PIM) routing.
You need
.Em MROUTING
and
.Em INET
with this.
Software using this can be found e.g. in
.Pa pkgsrc/net/xorp .
.It Cd options INET
Includes support for the TCP/IP protocol stack.
You almost certainly want this.
See
.Xr inet 4
for details.
.It Cd options INET6
Includes support for the IPv6 protocol stack.
See
.Xr inet6 4
for details.
Unlike
.Em INET ,
.Em INET6
enables multicast routing code as well.
This option requires
.Em INET
at this moment, but it should not.
.It Cd options ND6_DEBUG
The option sets the default value of net.inet6.icmp6.nd6_debug to 1,
for debugging IPv6 neighbor discovery protocol handling.
See
.Xr sysctl 3
for details.
.It Cd options IPSEC
Includes support for the IPsec protocol, using the implementation derived from
.Ox ,
relying on
.Xr opencrypto 9
to carry out cryptographic operations.
See
.Xr ipsec 4
for details.
.It Cd options IPSEC_DEBUG
Enables debugging code in IPsec stack.
See
.Xr ipsec 4
for details.
The
.Cd IPSEC
option includes support for IPsec Network Address Translator traversal
(NAT-T), as described in RFCs 3947 and 3948.
This feature might be patent-encumbered in some countries.
.It Cd options ALTQ
Enabled ALTQ (Alternate Queueing).
For simple rate-limiting, use
.Xr tbrconfig 8
to set up the interface transmission rate.
To use queueing disciplines, their appropriate kernel options should also
be defined (documented below).
Queueing disciplines are managed by
.Xr altqd 8 .
See
.Xr altq 9
for details.
.It Cd options ALTQ_HFSC
Include support for ALTQ-implemented HFSC (Hierarchical Fair Service Curve)
module.
HFSC supports both link-sharing and guaranteed real-time services.
HFSC employs a service curve based QoS model, and its unique feature
is an ability to decouple delay and bandwidth allocation.
Requires
.Em ALTQ_RED
to use the RED queueing discipline on HFSC classes, or
.Em ALTQ_RIO
to use the RIO queueing discipline on HFSC classes.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_PRIQ
Include support for ALTQ-implemented PRIQ (Priority Queueing).
PRIQ implements a simple priority-based queueing discipline.
A higher priority class is always served first.
Requires
.Em ALTQ_RED
to use the RED queueing discipline on HFSC classes, or
.Em ALTQ_RIO
to use the RIO queueing discipline on HFSC classes.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_WFQ
Include support for ALTQ-implemented WFQ (Weighted Fair Queueing).
WFQ implements a weighted-round robin scheduler for a set of queues.
A weight can be assigned to each queue to give a different proportion
of the link capacity.
A hash function is used to map a flow to one of a set of queues.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_FIFOQ
Include support for ALTQ-implemented FIFO queueing.
FIFOQ is a simple drop-tail FIFO (First In, First Out) queueing discipline.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_RIO
Include support for ALTQ-implemented RIO (RED with In/Out).
The original RIO has 2 sets of RED parameters; one for in-profile
packets and the other for out-of-profile packets.
At the ingress of the network, profile meters tag packets as IN or
OUT based on contracted profiles for customers.
Inside the network, IN packets receive preferential treatment by
the RIO dropper.
ALTQ/RIO has 3 drop precedence levels defined for the Assured Forwarding
PHB of DiffServ (RFC 2597).
This option assumes
.Em ALTQ .
.It Cd options ALTQ_BLUE
Include support for ALTQ-implemented Blue buffer management.
Blue is another active buffer management mechanism.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_FLOWVALVE
Include support for ALTQ-implemented Flowvalve.
Flowvalve is a simple implementation of a RED penalty box that identifies
and punishes misbehaving flows.
This option requires
.Em ALTQ_RED
and assumes
.Em ALTQ .
.It Cd options ALTQ_CDNR
Include support for ALTQ-implemented CDNR (diffserv traffic conditioner)
packet marking/manipulation.
Traffic conditioners are components to meter, mark, or drop incoming
packets according to some rules.
As opposed to queueing disciplines, traffic conditioners handle incoming
packets at an input interface.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_NOPCC
Disables use of processor cycle counter to measure time in ALTQ.
This option should be defined for a non-Pentium i386 CPU which does not
have TSC, SMP (per-CPU counters are not in sync), or power management
which affects processor cycle counter.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_IPSEC
Include support for IPsec in IPv4 ALTQ.
This option assumes
.Em ALTQ .
.It Cd options ALTQ_JOBS
Include support for ALTQ-implemented JoBS (Joint Buffer Management
and Scheduling).
This option assumes
.Em ALTQ .
.It Cd options ALTQ_AFMAP
Include support for an undocumented ALTQ feature that is used to map an IP
flow to an ATM VC (Virtual Circuit).
This option assumes
.Em ALTQ .
.It Cd options ALTQ_LOCALQ
Include support for ALTQ-implemented local queues.
Its practical use is undefined.
Assumes
.Em ALTQ .
.It Cd options SUBNETSARELOCAL
Sets default value for net.inet.ip.subnetsarelocal variable, which
controls whether non-directly-connected subnets of connected networks
are considered "local" for purposes of choosing the MSS for a TCP
connection.
This is mostly present for historic reasons and completely irrelevant if
you enable Path MTU discovery.
.It Cd options HOSTZEROBROADCAST
Sets default value for net.inet.ip.hostzerobroadcast variable, which
controls whether the zeroth host address of each connected subnet is
also considered a broadcast address.
Default value is "1", for compatibility with old systems; if this is
set to zero on all hosts on a subnet, you should be able to fit an extra
host per subnet on the
".0" address.
.It Cd options MCLSHIFT=value
This option is the base-2 logarithm of the size of mbuf clusters.
The
.Bx
networking stack keeps network packets in a linked
list, or chain, of kernel buffer objects called mbufs.
The system provides larger mbuf clusters as an optimization for
large packets, instead of using long chains for large packets.
The mbuf cluster size,
or
.Em MCLBYTES ,
must be a power of two, and is computed as two raised to the power
.Em MCLSHIFT .
On systems with Ethernet network adapters,
.Em MCLSHIFT
is often set to 11, giving 2048-byte mbuf clusters, large enough to
hold a 1500-byte Ethernet frame in a single cluster.
Systems with network interfaces supporting larger frame sizes like
ATM, FDDI, or HIPPI may perform better with
.Em MCLSHIFT
set to 12 or 13, giving mbuf cluster sizes of 4096 and 8192 bytes,
respectively.
.It Cd options NETATALK
Include support for the AppleTalk protocol stack.
The kernel provides provision for the
.Em Datagram Delivery Protocol
(DDP), providing SOCK_DGRAM support and AppleTalk routing.
This stack is used by the
.Em NETATALK
package, which adds support for AppleTalk server services via user
libraries and applications.
.It Cd options BLUETOOTH
Include support for the Bluetooth protocol stack.
See
.Xr bluetooth 4
for details.
.It Cd options IPNOPRIVPORTS
Normally, only root can bind a socket descriptor to a so-called
.Dq privileged
TCP port, that is, a port number in the range 0-1023.
This option eliminates those checks from the kernel.
This can be useful if there is a desire to allow daemons without
privileges to bind those ports, e.g., on firewalls.
The security tradeoffs in doing this are subtle.
This option should only be used by experts.
.It Cd options TCP_DEBUG
Record the last
.Em TCP_NDEBUG
TCP packets with SO_DEBUG set, and decode to the console if
.Em tcpconsdebug
is set.
.It Cd options TCP_NDEBUG
Number of packets to record for
.Em TCP_DEBUG .
Defaults to 100.
.It Cd options TCP_SENDSPACE=value
.It Cd options TCP_RECVSPACE=value
These options set the max TCP window size to other sizes than the default.
The TCP window sizes can be altered via
.Xr sysctl 8
as well.
.It Cd options TCP_INIT_WIN=value
This option sets the initial TCP window size for non-local connections,
which is used when the transmission starts.
The default size is 1, but if the machine should act more aggressively,
the initial size can be set to some other value.
The initial TCP window size can be set via
.Xr sysctl 8
as well.
.It Cd options TCP_SIGNATURE
Enable MD5 TCP signatures (RFC 2385) to protect BGP sessions.
.It Cd options IPFILTER_LOG
This option, in conjunction with
.Em pseudo-device ipfilter ,
enables logging of IP packets using IP-Filter.
.It Cd options IPFILTER_LOOKUP
This option enables the
IP-Filter
.Xr ippool 8
functionality to be enabled.
.It Cd options IPFILTER_COMPAT
This option enables older IP-Filter binaries to work.
.It Cd options IPFILTER_DEFAULT_BLOCK
This option sets the default policy of IP-Filter.
If it is set, IP-Filter will block packets by default.
.It Cd options BRIDGE_IPF
This option causes
.Em bridge
devices to use the IP and/or IPv6 filtering hooks, forming
a link-layer filter that uses protocol-layer rules.
This option assumes the presence of
.Em pseudo-device ipfilter .
.It Cd options MBUFTRACE
This option can help track down mbuf leaks.
When enabled, mbufs are tagged with the devices and protocols using them,
which slightly decreases network performance.
This additional information can be viewed with
.Xr netstat 1 :
.Dl Ic netstat Fl mssv
Not all devices or protocols support this option.
.El
.Ss Sysctl Related Options
.Bl -ohang
.It Cd options SYSCTL_DISALLOW_CREATE
Disallows the creation or deletion of nodes from the sysctl tree, as
well as the assigning of descriptions to nodes that lack them, by any
process.
These operations are still available to kernel sub-systems, including
loadable kernel modules.
.It Cd options SYSCTL_DISALLOW_KWRITE
Prevents processes from adding nodes to the sysctl tree that make
existing kernel memory areas writable.
Sections of kernel memory can still be read and new nodes that own
their own data may still be writable.
.It Cd options SYSCTL_DEBUG_SETUP
Causes the SYSCTL_SETUP routines to print a brief message when they
are invoked.
This is merely meant as an aid in determining the order in which
sections of the tree are created.
.It Cd options SYSCTL_DEBUG_CREATE
Prints a message each time
.Fn sysctl_create ,
the function that adds nodes to the tree, is called.
.It Cd options SYSCTL_INCLUDE_DESCR
Causes the kernel to include short, human readable descriptions for
nodes in the sysctl tree.
The descriptions can be retrieved programmatically (see
.Xr sysctl 3 ) ,
or by the sysctl binary itself (see
.Xr sysctl 8 ) .
The descriptions are meant to give an indication of the purpose and/or
effects of a given node's value, not replace the documentation for the
given subsystem as a whole.
.El
.Ss System V IPC Options
.Bl -ohang
.It Cd options SYSVMSG
Includes support for
.At V
style message queues.
See
.Xr msgctl 2 ,
.Xr msgget 2 ,
.Xr msgrcv 2 ,
.Xr msgsnd 2 .
.It Cd options SYSVSEM
Includes support for
.At V
style semaphores.
See
.Xr semctl 2 ,
.Xr semget 2 ,
.Xr semop 2 .
.It Cd options SEMMNI=value
Sets the number of
.At V
style semaphore identifiers.
The GENERIC config file for your port will have the default.
.It Cd options SEMMNS=value
Sets the number of
.At V
style semaphores in the system.
The GENERIC config file for your port will have the default.
.It Cd options SEMUME=value
Sets the maximum number of undo entries per process for
.At V
style semaphores.
The GENERIC config file for your port will have the default.
.It Cd options SEMMNU=value
Sets the number of undo structures in the system for
.At V
style semaphores.
The GENERIC config file for your port will have the default.
.It Cd options SYSVSHM
Includes support for
.At V
style shared memory.
See
.Xr shmat 2 ,
.Xr shmctl 2 ,
.Xr shmdt 2 ,
.Xr shmget 2 .
.It Cd options SHMMAXPGS=value
Sets the maximum number of
.At V
style shared memory pages that are available through the
.Xr shmget 2
system call.
Default value is 1024 on most ports.
See
.Pa /usr/include/machine/vmparam.h
for the default.
.El
.Ss VM Related Options
.Bl -ohang
.It Cd options NMBCLUSTERS=value
The number of mbuf clusters the kernel supports.
Mbuf clusters are MCLBYTES in size (usually 2k).
This is used to compute the size of the kernel VM map
.Em mb_map ,
which maps mbuf clusters.
The default value is calculated from the amount of physical memory.
Architectures without direct mapping also limit it based on the kmem_map size,
which is used as backing store.
Some archs limit the value with
.Sq NMBCLUSTERS_MAX .
See
.Pa /usr/include/machine/param.h
for those archs.
This value can be accessed via the kern.mbuf.nmbclusters sysctl variable.
Increase this value if you get
.Dq mclpool limit reached
messages.
.It Cd options NMBCLUSTERS_MAX=value
The upper limit of NMBCLUSTERS.
.It Cd options NKMEMPAGES=value
.It Cd options NKMEMPAGES_MIN=value
.It Cd options NKMEMPAGES_MAX=value
Size of kernel VM map
.Em kmem_map ,
in PAGE_SIZE-sized chunks (the VM page size; this value may be read
from the
.Xr sysctl 8
variable
.Em hw.pagesize
).
This VM map is used to map the kernel malloc arena.
The kernel attempts to auto-size this map based on the amount of
physical memory in the system.
Platform-specific code may place bounds on this computed size,
which may be viewed with the
.Xr sysctl 8
variable
.Em vm.nkmempages .
See
.Pa /usr/include/machine/param.h
for the default upper and lower bounds.
The related options
.Sq NKMEMPAGES_MIN
and
.Sq NKMEMPAGES_MAX
allow the bounds to be overridden in the kernel configuration file.
These options are provided in the event the computed value is
insufficient resulting in an
.Dq out of space in kmem_map
panic.
.It Cd options SB_MAX=value
Sets the max size in bytes that a socket buffer is allowed to occupy.
The default is 256k, but sometimes it needs to be increased, for example
when using large TCP windows.
This option can be changed via
.Xr sysctl 8
as well.
.It Cd options SOMAXKVA=value
Sets the maximum size of kernel virtual memory that the socket buffers
are allowed to use.
The default is 16MB, but in situations where for example large TCP
windows are used this value must also be increased.
This option can be changed via
.Xr sysctl 8
as well.
.It Cd options BUFCACHE=value
Size of the buffer cache as a percentage of total available RAM.
Ignored if BUFPAGES is also specified.
.It Cd options NBUF=value
Sets the number of buffer headers available, i.e., the number of
open files that may have a buffer cache entry.
Each buffer header
requires MAXBSIZE (machine dependent, but usually 65536) bytes.
The default value is machine dependent, but is usually equal to the
value of BUFPAGES.
.It Cd options BUFPAGES=value
These options set the number of pages available for the buffer cache.
Their default value is a machine dependent value, often calculated as
between 5% and 10% of total available RAM.
.It Cd options MAXTSIZ=bytes
Sets the maximum size limit of a process' text segment.
See
.Pa /usr/include/machine/vmparam.h
for the port-specific default.
.It Cd options DFLDSIZ=bytes
Sets the default size limit of a process' data segment, the value that
will be returned as the soft limit for
.Dv RLIMIT_DATA
(as returned by
.Xr getrlimit 2 ) .
See
.Pa /usr/include/machine/vmparam.h
for the port-specific default.
.It Cd options MAXDSIZ=bytes
Sets the maximum size limit of a process' data segment, the value that
will be returned as the hard limit for
.Dv RLIMIT_DATA
(as returned by
.Xr getrlimit 2 ) .
See
.Pa /usr/include/machine/vmparam.h
for the port-specific default.
.It Cd options DFLSSIZ=bytes
Sets the default size limit of a process' stack segment, the value that
will be returned as the soft limit for
.Dv RLIMIT_STACK
(as returned by
.Xr getrlimit 2 ) .
See
.Pa /usr/include/machine/vmparam.h
for the port-specific default.
.It Cd options MAXSSIZ=bytes
Sets the maximum size limit of a process' stack segment, the value that
will be returned as the hard limit for
.Dv RLIMIT_STACK
(as returned by
.Xr getrlimit 2 ) .
See
.Pa /usr/include/machine/vmparam.h
for the port-specific default.
.It Cd options DUMP_ON_PANIC=integer
Defaults to one.
If set to zero, the kernel will not dump to the dump device when
it panics, though dumps can still be forced via
.Xr ddb 4
with the
.Dq sync
command.
Note that this sets the value of the
.Em kern.dump_on_panic
.Xr sysctl 3
variable which may be changed at run time \(em see
.Xr sysctl 8
for details.
.It Cd options USE_TOPDOWN_VM
User space memory allocations (as made by
.Xr mmap 2 )
will be arranged in a
.Dq top down
fashion instead of the traditional
.Dq upwards from MAXDSIZ \&+ vm_daddr
method.
This includes the placement of
.Xr ld.so 1 .
Arranging memory in this manner allows either (or both of) the heap or
.Xr mmap 2
allocated space to grow larger than traditionally possible.
This option is not available on all ports, but is instead expected to be
offered on a port-by-port basis, after which some ports will commit to
using it by default.
See the files
.Pa /usr/include/uvm/uvm_param.h
for some implementation details, and
.Pa /usr/include/machine/vmparam.h
for port specific details including availability.
.It Cd options VMSWAP
Enable paging device/file support.
This option is on by default.
.It Cd options PDPOLICY_CLOCKPRO
Use CLOCK-Pro, an alternative page replace policy.
.El
.Ss Security Options
.Bl -ohang
.It Cd options INSECURE
Initializes the kernel security level with \-1 instead of 0.
This means that the system always starts in secure level \-1 mode, even when
running multiuser, unless the securelevel variable is set to value > \-1 in
.Pa /etc/rc.conf .
In this case the kernel security level will be raised to that value when the
.Pa /etc/rc.d/securelevel
script is run during system startup.
See the manual page for
.Xr init 8
for details on the implications of this.
The kernel secure level may manipulated by the superuser by altering the
.Em kern.securelevel
.Xr sysctl 3
variable (the secure level may only be lowered by a call from process ID 1,
i.e.,
.Xr init 8 ) .
See also
.Xr secmodel_securelevel 9 ,
.Xr sysctl 8
and
.Xr sysctl 3 .
.It Cd options VERIFIED_EXEC_FP_SHA256
Enables support for SHA256 hashes in Veriexec.
.It Cd options VERIFIED_EXEC_FP_SHA384
Enables support for SHA384 hashes in Veriexec.
.It Cd options VERIFIED_EXEC_FP_SHA512
Enables support for SHA512 hashes in Veriexec.
.It Cd options PAX_MPROTECT=value
Enables PaX MPROTECT,
.Xr mprotect 2
restrictions from the PaX project.
.Pp
The
.Ar value
is the default value for the
.Em global
knob, see
.Xr sysctl 3 .
If 0, PaX MPROTECT will be enabled only if explicitly set on programs
using
.Xr paxctl 8 .
If 1, PaX MPROTECT will be enabled for all programs.
Programs can be exempted using
.Xr paxctl 8 .
.Pp
See
.Xr security 7
for more details.
.It Cd options PAX_SEGVGUARD=value
Enables PaX Segvguard.
Requires
.Cd options FILEASSOC .
.Pp
The
.Ar value
is the default value for the
.Em global
knob, see
.Xr sysctl 3 .
If 0, PaX Segvguard will be enabled only if explicitly set on programs
using
.Xr paxctl 8 .
If 1, PaX Segvguard will be enabled to all programs, and exemption can
be done using
.Xr paxctl 8 .
.Pp
See
.Xr security 7
for more details.
.It Cd options PAX_ASLR=value
Enables PaX ASLR.
.Pp
The
.Ar value
is the default value for the
.Em global
knob, see
.Xr sysctl 3 .
If 0, PaX ASLR will be enabled only if explicitly set on programs
using
.Xr paxctl 8 .
If 1, PaX ASLR will be enabled to all programs, and exemption can
be done using
.Xr paxctl 8 .
.Pp
See
.Xr security 7
for more details.
.It Cd options USER_VA0_DISABLE_DEFAULT=value
Sets the initial value of the flag which controls whether user programs
can map virtual address 0.
The flag can be changed at runtime by
.Xr sysctl 3 .
.It Cd options KASAN
Enables Kernel Address Sanitizer.
Should not be used in conjunction with KLEAK.
.Em NOTE :
not available on all architectures.
.It Cd options KASLR
Enables Kernel ASLR.
This randomizes the location of the kernel image in memory.
.Em NOTE :
not available on all architectures.
.It Cd options KLEAK
Enables the KLEAK feature, that allows to detect kernel information leaks.
Should not be used in conjunction with KASAN.
.Em NOTE :
not available on all architectures.
.It Cd options SVS
Enables Separate Virtual Space.
On architectures that are designed to function with a shared address
space, this option explicitly isolates the kernel and user spaces.
.Em NOTE :
not available on all architectures.
.El
.Ss amiga-specific Options
.Bl -ohang
.It Cd options BB060STUPIDROM
When the bootloader (which passes AmigaOS ROM information) claims
we have a 68060 CPU without FPU, go look into the Processor
Configuration Register (PCR) to find out.
You need this with Amiga ROMs up to (at least) V40.xxx (OS3.1),
when you boot via the bootblocks and don't have a DraCo.
.It Cd options IOBZCLOCK=frequency
The IOBlix boards come with two different serial master clocks: older ones
use 24 MHz, newer ones use 22.1184 MHz.
The driver normally assumes the latter.
If your board uses 24 MHz, you can recompile your kernel with
options IOBZCLOCK=24000000
or patch the kernel variable iobzclock to the same value.
.It Cd options LIMITMEM=value
If there, limit the part of the first memory bank used by
.Nx
to value megabytes.
Default is unlimited.
.It Cd options P5PPC68KBOARD
Add special support for Phase5 mixed 68k+PPC boards.
Currently, this only affects rebooting from
.Nx
and is only needed on 68040+PPC, not on
68060+PPC; without this, affected machines will hang after
.Nx
has shut
down and will only restart after a keyboard reset or a power cycle.
.El
.Ss atari-specific Options
.Bl -ohang
.It Cd options DISKLABEL_AHDI
Include support for AHDI (native Atari) disklabels.
.It Cd options DISKLABEL_NBDA
Include support for
.Nx Ns /atari
labels.
If you don't set this option, it will be set automatically.
.Nx Ns /atari
will not work without it.
.It Cd options FALCON_SCSI
Include support for the 5380-SCSI configuration as found on the Falcon.
.It Cd options RELOC_KERNEL
If set, the kernel will relocate itself to TT-RAM, if possible.
This will give you a slightly faster system.
.Em Beware
that on some TT030 systems,
the system will frequently dump with MMU-faults with this option enabled.
.It Cd options SERCONSOLE
Allow the modem1-port to act as the system-console.
A carrier should be active on modem1 during system boot to active
the console functionality.
.It Cd options TT_SCSI
Include support for the 5380-SCSI configuration as found on the TT030
and Hades.
.El
.Ss i386-specific Options
.Bl -ohang
.It Cd options CPURESET_DELAY=value
Specifies the time (in millisecond) to wait before doing a hardware reset
in the last phase of a reboot.
This gives the user a chance to see error messages from the shutdown
operations (like NFS unmounts, buffer cache flush, etc ...).
Setting this to 0 will disable the delay.
Default is 2 seconds.
.It Cd options USER_LDT
Include i386-specific system calls for modifying the local descriptor table,
used by Windows emulators.
.It Cd options PAE
Enable PAE (Physical Address Extension) mode.
PAE permits up to 36 bits physical addressing (64GB of physical
memory), and turns physical addresses to 64 bits entities in the
memory management subsystem.
Userland virtual address space remains at 32 bits (4GB).
PAE mode is required to enable the NX/XD (No-eXecute/eXecute Disable)
bit for pages, which allows marking certain ones as not being executable.
Any attempt to execute code from such a page will raise an exception.
.It Cd options REALBASEMEM=integer
Overrides the base memory size passed in from the boot block.
(Value given in kilobytes.)
Use this option only if the boot block reports the size incorrectly.
(Note that some BIOSes put the extended BIOS
data area at the top of base memory, and therefore report a smaller
base memory size to prevent programs overwriting it.
This is correct behavior, and you should not use the
.Em REALBASEMEM
option to access this memory).
.It Cd options SPECTRE_V2_GCC_MITIGATION=1
Enable GCC-specific Spectre variant 2 mitigations.
For 32-bit kernels this means these options:
.Bd -literal -offset indent
-mindirect-branch=thunk -mindirect-branch-register
.Ed
.Pp
For 64-bit kernels this means these options:
.Bd -literal -offset indent
-mindirect-branch=thunk-inline -mindirect-branch-register
.Ed
.It Cd options REALEXTMEM=integer
Overrides the extended memory size passed in from the boot block.
(Value given in kilobytes.
Extended memory does not include the first megabyte.)
Use this option only if the boot block reports the size incorrectly.
.It Cd options CYRIX_CACHE_WORKS
Relevant only to the Cyrix 486DLC CPU.
This option is used to turn on the cache in hold-flush mode.
It is not turned on by default because it is known to have problems in
certain motherboard implementations.
.It Cd options CYRIX_CACHE_REALLY_WORKS
Relevant only to the Cyrix 486DLC CPU.
This option is used to turn on the cache in write-back mode.
It is not turned on by default because it is known to have problems in
certain motherboard implementations.
In order for this option to take effect, option
.Em CYRIX_CACHE_WORKS
must also be specified.
.It Cd options PCIBIOS
Enable support for initializing the PCI bus using information from
the BIOS.
See
.Xr pcibios 4
for details.
.It Cd options MTRR
Include support for accessing MTRR registers from user-space.
See
.Xr i386_get_mtrr 2 .
.It Cd options BEEP_ONHALT
Make the system speaker emit several beeps when it is completely safe to
power down the computer after a
.Xr halt 8
command.
Requires
.Xr sysbeep 4
support.
.It Cd options BEEP_ONHALT_COUNT=times
Number of times to beep the speaker when
.Cd options BEEP_ONHALT
is enabled.
Defaults to 3.
.It Cd options BEEP_ONHALT_PITCH=hz
The tone frequency used when
.Cd options BEEP_ONHALT
option, in hertz.
Defaults to 1500.
.It Cd options BEEP_ONHALT_PERIOD=msecs
The duration of each beep when
.Cd options BEEP_ONHALT
is enabled, in milliseconds.
Defaults to 250.
.It Cd options MULTIBOOT
Makes the kernel Multiboot-compliant, allowing it to be booted through
a Multiboot-compliant boot manager such as GRUB.
See
.Xr multiboot 8
for more information.
.It Cd options SPLASHSCREEN
Display a splash screen during boot.
.El
.Ss isa-specific Options
Options specific to
.Xr isa 4
busses.
.Bl -ohang
.It Cd options PCIC_ISA_ALLOC_IOBASE=address, PCIC_ISA_ALLOC_IOSIZE=size
Control the section of IO bus space used for PCMCIA bus space mapping.
Ideally the probed defaults are satisfactory, however in practice
that is not always the case.
See
.Xr pcmcia 4
for details.
.It Cd options PCIC_ISA_INTR_ALLOC_MASK=mask
Controls the allowable interrupts that may be used for PCMCIA
devices.
This mask is a logical-or of power-of-2s of allowable interrupts:
.Bd -literal -offset 04n
.Em "IRQ Val      IRQ Val      IRQ Val       IRQ Val"
 0  0x0001    4  0x0010    8  0x0100    12  0x1000
 1  0x0002    5  0x0020    9  0x0200    13  0x2000
 2  0x0004    6  0x0040   10  0x0400    14  0x4000
 3  0x0008    7  0x0080   11  0x0800    15  0x8000
.Ed
.It Cd options PCKBC_CNATTACH_SELFTEST
Perform a self test of the keyboard controller before attaching it as a
console.
This might be necessary on machines where we boot on cold iron, and
pckbc refuses to talk until we request a self test.
Currently only the netwinder port uses it.
.It Cd options PCKBD_CNATTACH_MAY_FAIL
If this option is set the PS/2 keyboard will not be used as the console
if it cannot be found during boot.
This allows other keyboards, like USB, to be the console keyboard.
.It Cd options PCKBD_LAYOUT=layout
Sets the default keyboard layout, see
.Xr pckbd 4 .
.El
.Ss m68k-specific Options
.Bl -ohang
.It Cd options FPU_EMULATE
Include support for MC68881/MC68882 emulator.
.It Cd options FPSP
Include support for 68040 floating point.
.It Cd options M68020,M68030,M68040,M68060
Include support for a specific CPU,
at least one (the one you are using) should be specified.
.It Cd options M060SP
Include software support for 68060.
This provides emulation of unimplemented
integer instructions as well as emulation of unimplemented floating point
instructions and data types and software support for floating point traps.
.El
.Ss powerpc-specific Options (OEA Only)
.Bl -ohang
.It Cd options PMAP_MEMLIMIT=value
Limit the amount of memory seen by the kernel to
.Ar value
bytes.
.It Cd options PTEGCOUNT=value
Specify the size of the page table as
.Ar value
PTE groups.
Normally, one PTEG is allocated per physical page frame.
.El
.Ss sparc-specific Options
.Bl -ohang
.It Cd options AUDIO_DEBUG
Enable simple event debugging of the logging of the
.Xr audio 4
device.
.It Cd options BLINK
Enable blinking of LED.
Blink rate is full cycle every N seconds for
N < then current load average.
See
.Xr getloadavg 3 .
.\" .It Cd options COLORFONT_CACHE
.\" What does this do?
.It Cd options COUNT_SW_LEFTOVERS
Count how many times the sw SCSI device has left 3, 2, 1 and 0 in the
sw_3_leftover, sw_2_leftover, sw_1_leftover, and sw_0_leftover
variables accessible from
.Xr ddb 4 .
See
.Xr sw 4 .
.It Cd options DEBUG_ALIGN
Adds debugging messages calls when user-requested alignment fault
handling happens.
.It Cd options DEBUG_EMUL
Adds debugging messages calls for emulated floating point and
alignment fixing operations.
.It Cd options EXTREME_DEBUG
Adds debugging functions callable from
.Xr ddb 4 .
The debug_pagetables, test_region and print_fe_map
functions print information about page tables for the SUN4M
platforms only.
.It Cd options EXTREME_EXTREME_DEBUG
Adds extra info to
.Em options EXTREME_DEBUG .
.It Cd options FPU_CONTEXT
Make
.Em options COMPAT_SVR4
getcontext and setcontext include floating point registers.
.It Cd options MAGMA_DEBUG
Adds debugging messages to the
.Xr magma 4
device.
.It Cd options RASTERCONS_FULLSCREEN
Use the entire screen for the console.
.It Cd options RASTERCONS_SMALLFONT
Use the Fixed font on the console, instead of the normal font.
.It Cd options SUN4
Support sun4 class machines.
.It Cd options SUN4C
Support sun4c class machines.
.It Cd options SUN4M
Support sun4m class machines.
.It Cd options SUN4_MMU3L
.\" XXX ???
Enable support for sun4 3-level MMU machines.
.It Cd options V9
Enable SPARC V9 assembler in
.Xr ddb 4 .
.El
.Ss sparc64-specific Options
.Bl -ohang
.It Cd options AUDIO_DEBUG
Enable simple event debugging of the logging of the
.Xr audio 4
device.
.It Cd options BLINK
Enable blinking of LED.
Blink rate is full cycle every N seconds for
N < then current load average.
See
.Xr getloadavg 3 .
.El
.Ss x68k-specific Options
.Bl -ohang
.It Cd options EXTENDED_MEMORY
Include support for extended memory, e.g., TS-6BE16 and 060turbo on-board.
.It Cd options JUPITER
Include support for Jupiter-X MPU accelerator
.It Cd options ZSCONSOLE,ZSCN_SPEED=value
Use the built-in serial port as the system-console.
Speed is specified in bps, defaults to 9600.
.It Cd options ITE_KERNEL_ATTR=value
Set the kernel message attribute for ITE.
Value, an integer, is a logical or of the following values:
.Bl -tag -width 4n -compact -offset indent
.It 1
color inversed
.It 2
underlined
.It 4
bolded
.El
.El
.Ss x86-specific Options
.Bl -ohang
.It Cd options NO_PCI_MSI_MSIX
Disable support for MSI/MSIX in the kernel.
See
.Xr pci_msi 9
for details of MSI/MSIX support
.It Cd options NO_PREEMPTION
Disables
.Xr kpreempt 9
support in the kernel.
.El
.\" The following requests should be uncommented and used where appropriate.
.\" .Sh FILES
.\" .Sh EXAMPLES
.Sh SEE ALSO
.Xr config 1 ,
.Xr gcc 1 ,
.Xr gdb 1 ,
.Xr ktrace 1 ,
.Xr quota 1 ,
.Xr vndcompress 1 ,
.Xr gettimeofday 2 ,
.Xr i386_get_mtrr 2 ,
.Xr i386_iopl 2 ,
.Xr msgctl 2 ,
.Xr msgget 2 ,
.Xr msgrcv 2 ,
.Xr msgsnd 2 ,
.Xr ntp_adjtime 2 ,
.Xr ntp_gettime 2 ,
.Xr reboot 2 ,
.Xr semctl 2 ,
.Xr semget 2 ,
.Xr semop 2 ,
.Xr shmat 2 ,
.Xr shmctl 2 ,
.Xr shmdt 2 ,
.Xr shmget 2 ,
.Xr sysctl 3 ,
.Xr apm 4 ,
.Xr ddb 4 ,
.Xr inet 4 ,
.Xr md 4 ,
.Xr pcibios 4 ,
.Xr pcmcia 4 ,
.Xr ppp 4 ,
.Xr userconf 4 ,
.Xr vnd 4 ,
.Xr wscons 4 ,
.Xr config 5 ,
.Xr edquota 8 ,
.Xr init 8 ,
.Xr mdsetimage 8 ,
.Xr mount_cd9660 8 ,
.Xr mount_fdesc 8 ,
.Xr mount_kernfs 8 ,
.Xr mount_lfs 8 ,
.Xr mount_mfs 8 ,
.Xr mount_msdos 8 ,
.Xr mount_nfs 8 ,
.Xr mount_ntfs 8 ,
.Xr mount_null 8 ,
.Xr mount_portal 8 ,
.Xr mount_procfs 8 ,
.Xr mount_udf 8 ,
.Xr mount_umap 8 ,
.Xr mount_union 8 ,
.Xr mrouted 8 ,
.Xr newfs_lfs 8 ,
.Xr ntpd 8 ,
.Xr quotaon 8 ,
.Xr rpc.rquotad 8 ,
.Xr sysctl 8 ,
.Xr in_getifa 9 ,
.Xr kernhist 9
.Sh HISTORY
The
.Nm
man page first appeared in
.Nx 1.3 .