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