5c7955abff
Sponsored by: The FreeBSD Foundation MFC after: 2 weeks Differential revision: https://reviews.freebsd.org/D9258
179 lines
6.0 KiB
Groff
179 lines
6.0 KiB
Groff
.\"-
|
|
.\" Copyright (c) 2007 Xin LI
|
|
.\" Copyright (c) 2017 The FreeBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Part of this documentation was written by
|
|
.\" Konstantin Belousov <kib@FreeBSD.org> under sponsorship
|
|
.\" from the FreeBSD Foundation.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 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.
|
|
.\"
|
|
.\" THIS DOCUMENTATION IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
|
|
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
|
|
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
|
|
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
|
|
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
|
|
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\"-
|
|
.\" Copyright (c) 2005, 2006 The NetBSD Foundation, Inc.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 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.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
|
|
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
|
|
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
|
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
|
|
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
|
|
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
|
|
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
|
|
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
|
|
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
|
|
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
|
.\" POSSIBILITY OF SUCH DAMAGE.
|
|
.\"
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd January 20, 2017
|
|
.Dt TMPFS 5
|
|
.Os
|
|
.Sh NAME
|
|
.Nm tmpfs
|
|
.Nd "in-memory file system"
|
|
.Sh SYNOPSIS
|
|
To compile this driver into the kernel,
|
|
place the following line in your
|
|
kernel configuration file:
|
|
.Bd -ragged -offset indent
|
|
.Cd "options TMPFS"
|
|
.Ed
|
|
.Pp
|
|
Alternatively, to load the driver as a
|
|
module at boot time, place the following line in
|
|
.Xr loader.conf 5 :
|
|
.Bd -literal -offset indent
|
|
tmpfs_load="YES"
|
|
.Ed
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
driver implements an in-memory, or
|
|
.Tn tmpfs
|
|
file system.
|
|
The filesystem stores both file metadata and data in main memory.
|
|
This allows very fast and low latency accesses to the data.
|
|
The data is volatile.
|
|
An umount or system reboot invalidates it.
|
|
These properties make the filesystem's mounts suitable for fast
|
|
scratch storage, like
|
|
.Pa /tmp .
|
|
.Pp
|
|
If the system becomes low on memory and swap is configured (see
|
|
.Xr swapon 8 ),
|
|
the system can transfer file data to swap space, freeing memory
|
|
for other needs.
|
|
Metadata, including the directory content, is never swapped out by the
|
|
current implementation.
|
|
Keep this in mind when planning the mount limits, especially when expecting
|
|
to place many small files on a tmpfs mount.
|
|
.Pp
|
|
When
|
|
.Xr mmap 2
|
|
is used on a file from a tmpfs mount, the swap VM object managing the
|
|
file pages is used to implement mapping and avoid double-copying of
|
|
the file data.
|
|
This quirk causes process inspection tools, like
|
|
.Xr procstat 1 ,
|
|
to report anonymous memory mappings instead of file mappings.
|
|
.Sh OPTIONS
|
|
The following options are available when
|
|
mounting
|
|
.Nm
|
|
file systems:
|
|
.Bl -tag -width "It Cm maxfilesize"
|
|
.It Cm gid
|
|
Specifies the group ID of the root inode of the file system.
|
|
Defaults to the mount point's GID.
|
|
.It Cm uid
|
|
Specifies the user ID of the root inode of the file system.
|
|
Defaults to the mount point's UID.
|
|
.It Cm mode
|
|
Specifies the mode (in octal notation) of the root inode of the file system.
|
|
Defaults to the mount point's mode.
|
|
.It Cm nonc
|
|
Do not use namecache to resolve names to files for the created mount.
|
|
This saves memory, but currently might impair scalability for highly
|
|
used mounts on large machines.
|
|
.It Cm inodes
|
|
Specifies the maximum number of nodes available to the file system.
|
|
If not specified, the file system chooses a reasonable maximum based on
|
|
the file system size, which can be limited with the
|
|
.Cm size
|
|
option.
|
|
.It Cm size
|
|
Specifies the total file system size in bytes.
|
|
If zero (the default) or a value larger than SIZE_MAX - PAGE_SIZE
|
|
is given, the available amount of memory (including
|
|
main memory and swap space) will be used.
|
|
.It Cm maxfilesize
|
|
Specifies the maximum file size in bytes.
|
|
Defaults to the maximum possible value.
|
|
.El
|
|
.Sh EXAMPLES
|
|
To mount a
|
|
.Nm
|
|
memory file system:
|
|
.Pp
|
|
.Dl "mount -t tmpfs tmpfs /tmp"
|
|
.Sh SEE ALSO
|
|
.Xr procstat 1 ,
|
|
.Xr nmount 2 ,
|
|
.Xr mmap 2 ,
|
|
.Xr unmount 2 ,
|
|
.Xr fstab 5 ,
|
|
.Xr mdmfs 8 ,
|
|
.Xr mount 8 ,
|
|
.Xr swapinfo 8 ,
|
|
.Xr swapon 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
driver first appeared in
|
|
.Fx 7.0 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The
|
|
.Nm
|
|
kernel implementation was written by
|
|
.An Julio M. Merino Vidal Aq Mt jmmv@NetBSD.org
|
|
as a Google Summer of Code project.
|
|
.Pp
|
|
.An Rohit Jalan
|
|
and others ported it from
|
|
.Nx
|
|
to
|
|
.Fx .
|
|
.Pp
|
|
This manual page was written by
|
|
.An Xin LI Aq Mt delphij@FreeBSD.org .
|