.\" Copyright (c) 1992, 1993, 1994 .\" The Regents of the University of California. All rights reserved. .\" All rights reserved. .\" .\" This code is derived from software donated to Berkeley by .\" Jan-Simon Pendry and from John Heidemann of the UCLA Ficus project. .\" .\" 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_umap.8 8.4 (Berkeley) 5/1/95 .\" .Dd "May 1, 1995" .Dt MOUNT_UMAP 8 .Os BSD 4.4 .Sh NAME .Nm mount_umap .Nd sample file system layer .Sh SYNOPSIS .Nm mount_umap .Op Fl o Ar options .Ar target .Ar mount-point .Ar uid-mapfile .Ar gid-mapfile .Sh DESCRIPTION The .Nm mount_umap command is used to mount a sub-tree of an existing file system that uses a different set of uids and gids than the local system. Such a file system could be mounted from a remote site via NFS or it could be a file system on removable media brought from some foreign location that uses a different password file. .Pp The options are as follows: .Bl -tag -width indent .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. .El .Pp The .Nm mount_umap command uses a set of files provided by the user to make correspondences between uids and gids in the sub-tree's original environment and some other set of ids in the local environment. For instance, user smith might have uid 1000 in the original environment, while having uid 2000 in the local environment. The .Nm mount_umap command allows the subtree from smith's original environment to be mapped in such a way that all files with owning uid 1000 look like they are actually owned by uid 2000. .Pp .Em target should be the current location of the sub-tree in the local system's name space. .Em mount-point should be a directory where the mapped subtree is to be placed. .Em uid-mapfile and .Em gid-mapfile describe the mappings to be made between identifiers. Briefly, the format of these files is a count of the number of mappings on the first line, with each subsequent line containing a single mapping. Each of these mappings consists of an id from the original environment and the corresponding id in the local environment, separated by white space. .Em uid-mapfile should contain all uid mappings, and .Em gid-mapfile should contain all gid mappings. Any uids not mapped in .Em uid-mapfile will be treated as user NOBODY, and any gids not mapped in .Em gid-mapfile will be treated as group NULLGROUP. At most 64 uids can be mapped for a given subtree, and at most 16 groups can be mapped by a given subtree. .Pp The mapfiles can be located anywhere in the file hierarchy, but they must be owned by root, and they must be writable only by root. .Nm mount_umap will refuse to map the sub-tree if the ownership or permissions on these files are improper. It will also balk if the count of mappings in the first line of the map files is not correct. .Pp The layer created by the .Nm mount_umap command is meant to serve as a simple example of file system layering. It is not meant for production use. The implementation is not very sophisticated. .Sh SEE ALSO .Xr mount 8 , .Xr mount_null 8 .Sh HISTORY The .Nm mount_umap utility first appeared in 4.4BSD.