From 4f6862b1d577acf06e8f06b8abe7e0a338126958 Mon Sep 17 00:00:00 2001 From: John Heidemann Date: Thu, 9 Jul 1992 20:47:37 -0800 Subject: [PATCH] date and time created 92/07/09 13:47:37 by heideman SCCS-vsn: sbin/mount_null/mount_null.8 5.1 --- usr/src/sbin/mount_null/mount_null.8 | 49 ++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 usr/src/sbin/mount_null/mount_null.8 diff --git a/usr/src/sbin/mount_null/mount_null.8 b/usr/src/sbin/mount_null/mount_null.8 new file mode 100644 index 0000000000..b3f7e97b10 --- /dev/null +++ b/usr/src/sbin/mount_null/mount_null.8 @@ -0,0 +1,49 @@ +.\" +.\" Copyright (c) 1992 The Regents of the University of California +.\" Copyright (c) 1990, 1992 Jan-Simon Pendry +.\" All rights reserved. +.\" +.\" This code is derived from software donated to Berkeley by +.\" Jan-Simon Pendry and the null layer from John Heidemann of +.\" the UCLA Ficus proejct. +.\" +.\" +.\" %sccs.include.redist.roff% +.\" +.\" @(#)mount_null.8 5.1 (Berkeley) %G% +.\" +.\" +.Dd +.Dt MOUNT_NULL 8 +.Os BSD 4.4 +.Sh NAME +.Nm mount_null +.Nd mount a null layer, making a virtual copy of an existing filesystem sub-tree +.Sh SYNOPSIS +.Nm mount_null +.Op Fl F Ar fsoptions +.Ar target mount-point +.Sh DESCRIPTION +The +.Nm mount_null +command makes a sub-tree of an existing filesystem visible +in another part of the global filesystem namespace. +This allows existing files and directories to be accessed +using a different pathname. +.Pp +Virtual file system sub-trees created by the null layer should +be identical to those created by the loopback +The virtual copy of a file system sub-tree created by the null +layer should be nearly identical to one created by +.Xr mount_lofs 8 . +The purpose of the null layer is to serve as a basis for future +layer development. +.Pp +An example of a layer constructed from the null layer is +the umap layer (see +.Xr mount_umap 8 ). +.Sh HISTORY +The +loopback filesystem +is +.Ud -- 2.20.1