1.\" 2.\" Copyright (c) 2008 Daniel Gerzo 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS DOCUMENTATION IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24.\" 25.Dd March 15, 2022 26.Dt NULLFS 4 27.Os 28.Sh NAME 29.Nm nullfs 30.Nd "null file system" 31.Sh SYNOPSIS 32To enable support for this driver, 33place the following line in the kernel configuration file: 34.Bd -ragged -offset indent 35.Cd "options NULLFS" 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 42nullfs_load="YES" 43.Ed 44.Sh DESCRIPTION 45The 46.Nm 47driver will permit the 48.Fx 49kernel to mount a loopback file system sub-tree. 50.Sh EXAMPLES 51To mount a 52.Nm 53file system: 54.Pp 55.Dl "mount_nullfs /usr/ports /home/devel/ports" 56.Pp 57It is also possible to define an entry in 58.Xr fstab 5 59that looks similar to: 60.Pp 61.Bd -literal 62/usr/ports /home/devel/ports nullfs rw 0 0 63.Ed 64.Sh SEE ALSO 65.Xr fstab 5 , 66.Xr mount_nullfs 8 67.Sh HISTORY 68The 69.Nm 70layer first appeared in 71.Bx 4.4 . 72.Sh AUTHORS 73.An -nosplit 74The 75.Nm 76kernel implementation was written by 77.An John Heideman . 78.Pp 79This manual page was written by 80.An Daniel Gerzo Aq Mt danger@FreeBSD.org . 81