1.\" Copyright (c) 1994
2.\" The Regents of the University of California. All rights reserved.
3.\"
4.\" This code is derived from software donated to Berkeley by
5.\" Jan-Simon Pendry.
6.\"
7.\" Redistribution and use in source and binary forms, with or without
8.\" modification, are permitted provided that the following conditions
--- 19 unchanged lines hidden (view full) ---
28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33.\" SUCH DAMAGE.
34.\"
35.\" @(#)mount_union.8 8.6 (Berkeley) 3/27/94
36.\" $FreeBSD: head/sbin/mount_unionfs/mount_unionfs.8 77042 2001-05-23 14:58:19Z ru $
37.\"
38.Dd March 27, 1994
39.Dt MOUNT_UNIONFS 8
40.Os
41.Sh NAME
42.Nm mount_unionfs
43.Nd mount union filesystems
44.Sh SYNOPSIS
45.Nm
46.Op Fl br
47.Op Fl o Ar options
48.Ar directory
49.Ar uniondir
50.Sh DESCRIPTION
--- 30 unchanged lines hidden (view full) ---
81Options are specified with a
82.Fl o
83flag followed by a comma separated string of options.
84See the
85.Xr mount 8
86man page for possible options and their meanings.
87.It Fl r
88Hide the lower layer completely in the same way as mounting with
89.Xr mount_nullfs 8 .
90.El
91.Pp
92To enforce filesystem security, the user mounting the filesystem
93must be superuser or else have write permission on the mounted-on
94directory.
95.Pp
96Filenames are looked up in the upper layer and then in the
97lower layer.
--- 44 unchanged lines hidden (view full) ---
142option to
143.Xr mount 8
144which only applies the union operation to the mount point itself,
145and then only for lookups.
146.Sh EXAMPLES
147The commands
148.Bd -literal -offset indent
149mount -t cd9660 -o ro /dev/cd0a /usr/src
150mount -t unionfs /var/obj /usr/src
151.Ed
152.Pp
153mount the CD-ROM drive
154.Pa /dev/cd0a
155on
156.Pa /usr/src
157and then attaches
158.Pa /var/obj
159on top.
160For most purposes the effect of this is to make the
161source tree appear writable
162even though it is stored on a CD-ROM.
163.Pp
164The command
165.Bd -literal -offset indent
166mount -t unionfs -o -b /sys $HOME/sys
167.Ed
168.Pp
169attaches the system source tree below the
170.Pa sys
171directory in the user's home directory.
172This allows individual users to make private changes
173to the source, and build new kernels, without those
174changes becoming visible to other users.
--- 40 unchanged lines hidden ---
2.\" The Regents of the University of California. All rights reserved.
3.\"
4.\" This code is derived from software donated to Berkeley by
5.\" Jan-Simon Pendry.
6.\"
7.\" Redistribution and use in source and binary forms, with or without
8.\" modification, are permitted provided that the following conditions
--- 19 unchanged lines hidden (view full) ---
28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33.\" SUCH DAMAGE.
34.\"
35.\" @(#)mount_union.8 8.6 (Berkeley) 3/27/94
36.\" $FreeBSD: head/sbin/mount_unionfs/mount_unionfs.8 77042 2001-05-23 14:58:19Z ru $
37.\"
38.Dd March 27, 1994
39.Dt MOUNT_UNIONFS 8
40.Os
41.Sh NAME
42.Nm mount_unionfs
43.Nd mount union filesystems
44.Sh SYNOPSIS
45.Nm
46.Op Fl br
47.Op Fl o Ar options
48.Ar directory
49.Ar uniondir
50.Sh DESCRIPTION
--- 30 unchanged lines hidden (view full) ---
81Options are specified with a
82.Fl o
83flag followed by a comma separated string of options.
84See the
85.Xr mount 8
86man page for possible options and their meanings.
87.It Fl r
88Hide the lower layer completely in the same way as mounting with
89.Xr mount_nullfs 8 .
90.El
91.Pp
92To enforce filesystem security, the user mounting the filesystem
93must be superuser or else have write permission on the mounted-on
94directory.
95.Pp
96Filenames are looked up in the upper layer and then in the
97lower layer.
--- 44 unchanged lines hidden (view full) ---
142option to
143.Xr mount 8
144which only applies the union operation to the mount point itself,
145and then only for lookups.
146.Sh EXAMPLES
147The commands
148.Bd -literal -offset indent
149mount -t cd9660 -o ro /dev/cd0a /usr/src
150mount -t unionfs /var/obj /usr/src
151.Ed
152.Pp
153mount the CD-ROM drive
154.Pa /dev/cd0a
155on
156.Pa /usr/src
157and then attaches
158.Pa /var/obj
159on top.
160For most purposes the effect of this is to make the
161source tree appear writable
162even though it is stored on a CD-ROM.
163.Pp
164The command
165.Bd -literal -offset indent
166mount -t unionfs -o -b /sys $HOME/sys
167.Ed
168.Pp
169attaches the system source tree below the
170.Pa sys
171directory in the user's home directory.
172This allows individual users to make private changes
173to the source, and build new kernels, without those
174changes becoming visible to other users.
--- 40 unchanged lines hidden ---