.\"	$NetBSD: mount_tmpfs.8,v 1.8 2005/12/24 13:02:53 jmmv Exp $
.\"
.\" Copyright (c) 2005 The NetBSD Foundation, Inc.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Julio M. Merino Vidal, developed as part of Google's Summer of Code
.\" 2005 program.
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.Dd December 24, 2005
.Dt MOUNT_TMPFS 8
.Os
.Sh NAME
.Nm mount_tmpfs
.Nd mount an efficient memory file system
.Sh SYNOPSIS
.Nm
.Op Fl g Ar group
.Op Fl m Ar mode
.Op Fl n Ar nodes
.Op Fl o Ar options
.Op Fl s Ar size
.Op Fl u Ar user
.Ar tmpfs
.Ar mount_point
.Sh DESCRIPTION
The
.Nm
command attaches an instance of the efficient memory file system to the
global file system namespace.
The directory specified by
.Ar mount_point
is converted to an absolute path before use and its attributes (owner,
group and mode) are inherited unless explicitly overriden by the options
described below.
.Pp
The following options are supported:
.Bl -tag -width XoXoptions
.It Fl g Ar group
Specifies the group name or GID of the root inode of the file system.
Defaults to the mount point's GID.
.It Fl m Ar mode
Specifies the mode (in octal notation) of the root inode of the file system.
Defaults to the mount point's mode.
.It Fl n Ar nodes
Specifies the maximum number of nodes available to the file system.
.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.
.It Fl s Ar size
Specifies the total file system size in bytes.
If zero is given (the default), the available amount of memory (including
main memory and swap space) will be used.
Note that four megabytes are always reserved for the system and cannot
be assigned to the file system.
.It Fl u Ar user
Specifies the user name or UID of the root inode of the file system.
Defaults to the mount point's UID.
.El
.Pp
Every option that accepts a numerical value as its argument can take a
trailing
.Sq b
to indicate bytes (the default), a trailing
.Sq k
to indicate kilobytes, a trailing
.Sq M
to indicate megabytes or a trailing
.Sq G
to indicate gigabytes.
Note that both lowercase and uppercase forms of these letters are allowed.
.Sh EXAMPLES
The following command mounts a tmpfs instance over the
.Pa /tmp
directory, inheriting its owner, group and mode settings:
.Pp
.Ic "mount -t tmpfs tmpfs /tmp"
.Pp
The following command mounts a tmpfs instance over the
.Pa /mnt
directory, setting a 20 megabytes limit in space, owned by the
.Sq joe
user and belonging to the
.Sq users
group, with a restricted 0700 mode:
.Pp
.Ic "mount -t tmpfs -o -s20M -o -ujoe -o -gusers -o -m0700 tmpfs /mnt"
.Pp
See
.Pa /usr/share/examples/fstab/fstab.ramdisk
for some examples on how to add tmpfs entries to
.Pa /etc/fstab .
.Sh SEE ALSO
.Xr fstab 5 ,
.Xr mount 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Nx 4.0 .
.Sh BUGS
This file system is experimental.