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+.\"
+.\" Copyright (c) 2008 Daniel Gerzo
+.\" 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 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.
+.\"
+.Dd March 15, 2022
+.Dt NULLFS 4
+.Os
+.Sh NAME
+.Nm nullfs
+.Nd "null file system"
+.Sh SYNOPSIS
+To enable support for this driver,
+place the following line in the kernel configuration file:
+.Bd -ragged -offset indent
+.Cd "options NULLFS"
+.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
+nullfs_load="YES"
+.Ed
+.Sh DESCRIPTION
+The
+.Nm
+driver will permit the
+.Fx
+kernel to mount a loopback file system sub-tree.
+.Sh EXAMPLES
+To mount a
+.Nm
+file system:
+.Pp
+.Dl "mount_nullfs /usr/ports /home/devel/ports"
+.Pp
+It is also possible to define an entry in
+.Xr fstab 5
+that looks similar to:
+.Pp
+.Bd -literal
+/usr/ports	/home/devel/ports	nullfs		rw	0	0
+.Ed
+.Sh SEE ALSO
+.Xr fstab 5 ,
+.Xr mount_nullfs 8
+.Sh HISTORY
+The
+.Nm
+layer first appeared in
+.Bx 4.4 .
+.Sh AUTHORS
+.An -nosplit
+The
+.Nm
+kernel implementation was written by
+.An John Heideman .
+.Pp
+This manual page was written by
+.An Daniel Gerzo Aq Mt danger@FreeBSD.org .