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 --- |