1.\"- 2.\" SPDX-License-Identifier: BSD-2-Clause 3.\" 4.\" Copyright (c) 2020 Gordon Bergling 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 15.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25.\" SUCH DAMAGE. 26.\" 27.Dd April 27, 2020 28.Dt UNIONFS 4 29.Os 30.Sh NAME 31.Nm unionfs 32.Nd union mount file system 33.Sh SYNOPSIS 34To compile this driver into the kernel, 35place the following lines in your 36kernel configuration file: 37.Bd -ragged -offset indent 38.Cd "option UNIONFS" 39.Ed 40.Pp 41Alternatively, to load the driver as a 42module at boot time, place the following line in 43.Xr loader.conf 5 : 44.Bd -literal -offset indent 45unionfs_load="YES" 46.Ed 47.Sh DESCRIPTION 48The UNIONFS driver is an implementation of a stackable unification filesystem. 49.Sh SEE ALSO 50.Xr mount_unionfs 8 51.Sh STANDARDS 52.Rs 53.%T Union mounts in 4.4BSD-Lite 54.%A J. S. Pendry 55.%A M. K. McKusick 56.%R Proceedings of the USENIX Technical Conference on UNIX and Advanced Computing Systems 57.%D December 1995 58.Re 59.Pp 60.Rs 61.%T Jails: Confining the omnipotent root 62.%A P. H. Kamp 63.%A R. N. M. Watson 64.%R Proceedings of the Second International System Administration and Networking Conference (SANE2000) 65.%D May 2000 66.Re 67.Sh HISTORY 68The 69.Nm 70device driver first appeared in 71.Fx 5.0 . 72.Sh AUTHORS 73.An -nosplit 74The 75.Nm 76device driver was written by Jan-Simon Pendry for 77.Bx 4.4 78and 79.An Masanori OZAWA Aq Mt ozawa@ongs.co.jp 80reimplemented the handling of the locking for 81.Fx 7.0 . 82The manual page was written by 83.An Gordon Bergling Aq Mt gbe@FreeBSD.org . 84.Sh BUGS 85Please see the 86.Xr mount_unionfs 8 87manual page for a list of bugs regarding the 88.Nm 89filesystem. 90