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Diffstat (limited to 'sbin/mount_union/mount_union.8')
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diff --git a/sbin/mount_union/mount_union.8 b/sbin/mount_union/mount_union.8 deleted file mode 100644 index 163839e..0000000 --- a/sbin/mount_union/mount_union.8 +++ /dev/null @@ -1,214 +0,0 @@ -.\" Copyright (c) 1994 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" This code is derived from software donated to Berkeley by -.\" Jan-Simon Pendry. -.\" -.\" 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. -.\" 3. All advertising materials mentioning features or use of this software -.\" must display the following acknowledgement: -.\" This product includes software developed by the University of -.\" California, Berkeley and its contributors. -.\" 4. Neither the name of the University nor the names of its contributors -.\" may be used to endorse or promote products derived from this software -.\" without specific prior written permission. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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. -.\" -.\" @(#)mount_union.8 8.6 (Berkeley) 3/27/94 -.\" $FreeBSD$ -.\" -.Dd March 27, 1994 -.Dt MOUNT_UNION 8 -.Os BSD 4.4 -.Sh NAME -.Nm mount_union -.Nd mount union filesystems -.Sh SYNOPSIS -.Nm -.Op Fl br -.Op Fl o Ar options -.Ar directory -.Ar uniondir -.Sh DESCRIPTION -The -.Nm -command -attaches -.Ar directory -above -.Ar uniondir -in such a way that the contents of both directory trees remain visible. -By default, -.Ar directory -becomes the -.Em upper -layer and -.Ar uniondir -becomes the -.Em lower -layer. -.Pp -The options are as follows: -.Bl -tag -width indent -.It Fl b -Invert the default position, so that -.Ar directory -becomes the lower layer and -.Ar uniondir -becomes the upper layer. -However, -.Ar uniondir -remains the mount point. -.It Fl o -Options are specified with a -.Fl o -flag followed by a comma separated string of options. -See the -.Xr mount 8 -man page for possible options and their meanings. -.It Fl r -Hide the lower layer completely in the same way as mounting with -.Xr mount_null 8 . -.El -.Pp -To enforce filesystem security, the user mounting the filesystem -must be superuser or else have write permission on the mounted-on -directory. -.Pp -Filenames are looked up in the upper layer and then in the -lower layer. -If a directory is found in the lower layer, and there is no entry -in the upper layer, then a -.Em shadow -directory will be created in the upper layer. -It will be owned by the user who originally did the union mount, -with mode -.Dq rwxrwxrwx -(0777) modified by the umask in effect at that time. -.Pp -If a file exists in the upper layer then there is no way to access -a file with the same name in the lower layer. -If necessary, a combination of loopback and union mounts can be made -which will still allow the lower files to be accessed by a different -pathname. -.Pp -Except in the case of a directory, -access to an object is granted via the normal filesystem access checks. -For directories, the current user must have access to both the upper -and lower directories (should they both exist). -.Pp -Requests to create or modify objects in -.Ar uniondir -are passed to the upper layer with the exception of a few special cases. -An attempt to open for writing a file which exists in the lower layer -causes a copy of the -.Em entire -file to be made to the upper layer, and then for the upper layer copy -to be opened. -Similarly, an attempt to truncate a lower layer file to zero length -causes an empty file to be created in the upper layer. -Any other operation which would ultimately require modification to -the lower layer fails with -.Er EROFS . -.Pp -The union filesystem manipulates the namespace, rather than -individual filesystems. -The union operation applies recursively down the directory tree -now rooted at -.Ar uniondir . -Thus any filesystems which are mounted under -.Ar uniondir -will take part in the union operation. -This differs from the -.Em union -option to -.Xr mount 8 -which only applies the union operation to the mount point itself, -and then only for lookups. -.Sh EXAMPLES -The commands -.Bd -literal -offset indent -mount -t cd9660 -o ro /dev/cd0a /usr/src -mount -t union /var/obj /usr/src -.Ed -.Pp -mount the CD-ROM drive -.Pa /dev/cd0a -on -.Pa /usr/src -and then attaches -.Pa /var/obj -on top. -For most purposes the effect of this is to make the -source tree appear writable -even though it is stored on a CD-ROM. -.Pp -The command -.Bd -literal -offset indent -mount -t union -o -b /sys $HOME/sys -.Ed -.Pp -attaches the system source tree below the -.Pa sys -directory in the user's home directory. -This allows individual users to make private changes -to the source, and build new kernels, without those -changes becoming visible to other users. -Note that the files in the lower layer remain -accessible via -.Pa /sys . -.Sh SEE ALSO -.Xr intro 2 , -.Xr mount 2 , -.Xr unmount 2 , -.Xr fstab 5 , -.Xr mount 8 , -.Xr mount_null 8 -.Sh BUGS -THIS FILESYSTEM TYPE IS NOT YET FULLY SUPPORTED (READ: IT DOESN'T WORK) -AND USING IT MAY, IN FACT, DESTROY DATA ON YOUR SYSTEM. USE AT YOUR -OWN RISK. BEWARE OF DOG. SLIPPERY WHEN WET. -.Pp -This code also needs an owner in order to be less dangerous - serious -hackers can apply by sending mail to -.Aq hackers@FreeBSD.org -and announcing -their intent to take it over. -.Pp -Without whiteout support from the filesystem backing the upper layer, -there is no way that delete and rename operations on lower layer -objects can be done. -.Er EROFS -is returned for this kind of operations along with any others -which would make modifications to the lower layer, such as -.Xr chmod 1 . -.Pp -Running -.Xr find 1 -over a union tree has the side-effect of creating -a tree of shadow directories in the upper layer. -.Sh HISTORY -The -.Nm -command first appeared in -.Bx 4.4 . -It first worked in -.Fx Ns -(fill this in) . |