4d846d260e
The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch up to that fact and revert to their recommended match of BSD-2-Clause. Discussed with: pfg MFC After: 3 days Sponsored by: Netflix
139 lines
4.7 KiB
Groff
139 lines
4.7 KiB
Groff
.\"
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.\" SPDX-License-Identifier: BSD-2-Clause
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.\"
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.\" Copyright (c) 2019 The FreeBSD Foundation
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.\"
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.\" This documentation was written by BFF Storage Systems, LLC under
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.\" sponsorship from the FreeBSD Foundation.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.Dd July 31, 2019
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.Dt FUSEFS 5
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.Os
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.Sh NAME
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.Nm fusefs
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.Nd "File system in USErspace"
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.Sh SYNOPSIS
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To link into the kernel:
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.Bd -ragged -offset indent
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.Cd "options FUSEFS"
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.Ed
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.Pp
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To load as a loadable kernel module:
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.Pp
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.Dl "kldload fusefs"
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.Sh DESCRIPTION
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The
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.Nm
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driver implements a file system that is serviced by a userspace program.
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.Pp
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There are many uses for
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.Nm .
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Userspace daemons can access libraries or programming languages that cannot run
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in kernel-mode, for example.
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.Nm
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is also useful for developing and debugging file systems, because a crash of
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the daemon will not take down the entire operating system.
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Finally, the
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.Nm
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API is portable.
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Many daemons can run on multiple operating systems with minimal modifications.
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.Sh SYSCTL VARIABLES
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The following
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.Xr sysctl 8
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variables are available:
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.Bl -tag -width indent
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.It Va vfs.fusefs.kernelabi_major
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Major version of the FUSE kernel ABI supported by this driver.
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.It Va vfs.fusefs.kernelabi_minor
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Minor version of the FUSE kernel ABI supported by this driver.
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.It Va vfs.fusefs.data_cache_mode
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Controls how
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.Nm
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will cache file data for pre-7.23 file systems.
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A value of 0 will disable caching entirely.
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Every data access will be forwarded to the daemon.
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A value of 1 will select write-through caching.
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Reads will be cached in the VFS layer as usual.
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Writes will be immediately forwarded to the daemon, and also added to the cache.
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A value of 2 will select write-back caching.
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Reads and writes will both be cached, and writes will occasionally be flushed
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to the daemon by the page daemon.
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Write-back caching is usually unsafe, especially for FUSE file systems that
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require network access.
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.Pp
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FUSE file systems using protocol 7.23 or later specify their cache behavior
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on a per-mountpoint basis, ignoring this sysctl.
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.It Va vfs.fusefs.stats.filehandle_count
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Current number of open FUSE file handles.
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.It Va vfs.fusefs.stats.lookup_cache_hits
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Total number of lookup cache hits.
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.It Va vfs.fusefs.stats.lookup_cache_misses
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Total number of lookup cache misses.
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.It Va vfs.fusefs.stats.node_count
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Current number of allocated FUSE vnodes.
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.It Va vfs.fusefs.stats.ticket_count
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Current number of allocated FUSE tickets, which is roughly equal to the number
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of FUSE operations currently being processed by daemons.
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.\" Undocumented sysctls
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.\" ====================
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.\" vfs.fusefs.enforce_dev_perms: I don't understand it well enough.
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.\" vfs.fusefs.iov_credit: I don't understand it well enough
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.\" vfs.fusefs.iov_permanent_bufsize: I don't understand it well enough
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.El
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.Sh SEE ALSO
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.Xr mount_fusefs 8
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.Sh HISTORY
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The
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.Nm fuse
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driver was written as the part of the
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.Fx
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implementation of the FUSE userspace file system framework (see
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.Lk https://github.com/libfuse/libfuse )
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and first appeared in the
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.Pa sysutils/fusefs-kmod
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port, supporting
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.Fx 6.0 .
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It was added to the base system in
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.Fx 10.0 ,
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and renamed to
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.Nm
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for
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.Fx 12.1 .
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.Sh AUTHORS
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.An -nosplit
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The
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.Nm fuse
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driver was originally written by
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.An Csaba Henk
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as a Google Summer of Code project in 2005.
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It was further developed by
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.An Ilya Putsikau
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during Google Summer of Code 2011, and that version was integrated into the
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base system by
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.An Attilio Rao Aq Mt attilio@FreeBSD.org .
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.Pp
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This manual page was written by
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.An Alan Somers Aq Mt asomers@FreeBSD.org .
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