.\"	$OpenBSD: mount_kernfs.8,v 1.22 2004/11/24 16:56:38 ian Exp $
.\"	$NetBSD: mount_kernfs.8,v 1.6 1995/03/18 14:57:24 cgd Exp $
.\"
.\" Copyright (c) 1992, 1993, 1994
.\"	The Regents of the University of California.  All rights reserved.
.\" All rights reserved.
.\"
.\" This code is derived from software donated to Berkeley by
.\" Jan-Simon Pendry.
.\"
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    without specific prior written permission.
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.\"
.\"	@(#)mount_kernfs.8	8.2 (Berkeley) 3/27/94
.\"
.Dd March 27, 1994
.Dt MOUNT_KERNFS 8
.Os
.Sh NAME
.Nm mount_kernfs
.Nd mount the /kern file system
.Sh SYNOPSIS
.Nm mount_kernfs
.Op Fl o Ar options
.Ar /kern
.Ar mount_point
.Sh DESCRIPTION
The
.Nm
command attaches an instance of the kernel parameter
namespace to the global filesystem namespace.
The conventional mount point is
.Pa /kern .
This command is invoked by
.Xr mount 8
when using the syntax
.Bd -ragged -offset 4n
.Nm mount Op options
-t kernfs
.Ar /kern
.Ar mount_point
.Ed
.Pp
This command is normally executed by
.Xr mount 8
at boot time.
.Pp
The filesystem includes several regular files which can be read,
some of which can also be written.
The contents of the files are in a machine-independent format,
either a string, or an integer in decimal ASCII.
Where numbers are returned, a trailing newline character is also added.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl o Ar options
Options are specified with a
.Fl o
flag followed by a comma separated string of options.
See the
.Xr mount 8
man page for possible options and their meanings.
.El
.Pp
Statistics reported by
.Xr df 1
on the
.Pa /kern
filesystem will indicate the amount of
unwired/physical memory instead of
.Sq disk space ,
and the number of vnodes
used/allocated instead of
.Sq inodes .
The filesystem's block size is the system's page size.
.Sh FILES
.Bl -tag -width copyright -compact
.It Pa boottime
Time at which the system was last booted (decimal ASCII).
.It Pa byteorder
_BYTE_ORDER for this kernel.
.It Pa copyright
Kernel copyright message.
.It Pa hostname
The hostname, with a trailing newline.
The hostname can be changed by writing to this file.
A trailing newline will be stripped from the hostname being written.
.It Pa domainname
The domainname, with a trailing newline.
Behaves like a hostname.
.It Pa hz
Frequency of the system clock (decimal ASCII).
.It Pa ipsec
The currently configured IPsec Security Associations.
.It Pa loadavg
The 1, 5 and 15 minute load average in kernel fixed-point format.
The final integer is the fix-point scaling factor.
All numbers are in decimal ASCII.
.It Pa machine
Architecture this kernel was compiled for.
.It Pa model
Model of the processor this machine is running on.
.It Pa msgbuf
Kernel message buffer, also read by
.Xr syslogd 8 ,
through the
.Pa log
device, and by
.Xr dmesg 8 .
.It Pa ncpu
Number of CPUs in this machine.
.It Pa ostype
OS type for this kernel ("OpenBSD").
.It Pa osrelease
OS release number.
.It Pa osrev
OS revision number (BSD from
.Aq Pa sys/param.h ) .
.It Pa pagesize
Machine pagesize (decimal ASCII).
.It Pa posix
_POSIX_VERSION for this kernel.
.It Pa physmem
Number of pages of physical memory in the machine (decimal ASCII).
.\" .It Pa root
.\" the system root directory.
.\" In a chroot'ed environment,
.\" .Nm
.\" can be used to create a new
.\" .Pa /kern
.\" mount point.
.\" .Pa /kern/root
.\" will then refer to the system global root, not the current process root.
.It Pa rootdev
Root device.
.It Pa rrootdev
Raw root device.
.It Pa time
Second and microsecond value of the system clock.
Both numbers are in decimal ASCII.
.It Pa usermem
Number of pages of physical memory available for user processes.
.It Pa version
Kernel version string.
The head line for
.Pa /etc/motd
can be generated by running:
.Dq Ic "sed 1q /kern/version" .
.El
.Sh SEE ALSO
.Xr mount 2 ,
.Xr fstab 5 ,
.Xr dmesg 8 ,
.Xr mount 8 ,
.Xr syslogd 8 ,
.Xr umount 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Bx 4.4 .
.Sh CAVEATS
This filesystem may not be NFS-exported.
.Pp
Due to non-atomic operations and the potential for race conditions,
programs should not depend on information obtained from this filesystem.