4.4BSD/usr/share/man/cat8/mount_umap.0

MOUNT_UMAP(8)             BSD System Manager's Manual            MOUNT_UMAP(8)

NNAAMMEE
     mmoouunntt__uummaapp - sample file system layer

SSYYNNOOPPSSIISS
     mmoouunntt__uummaapp [--FF _f_s_o_p_t_i_o_n_s] _t_a_r_g_e_t _m_o_u_n_t_-_p_o_i_n_t _u_i_d_-_m_a_p_f_i_l_e _g_i_d_-_m_a_p_f_i_l_e

DDEESSCCRRIIPPTTIIOONN
     The mmoouunntt__uummaapp 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 loca-
     tion that uses a different password file.  The mmoouunntt__uummaapp 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 environ-
     ment.  The mmoouunntt__uummaapp 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.

     _t_a_r_g_e_t should be the current location of the sub-tree in the local sys-
     tem's name space.  _m_o_u_n_t_-_p_o_i_n_t should be a directory where the mapped
     subtree is to be placed.  _u_i_d_-_m_a_p_f_i_l_e and _g_i_d_-_m_a_p_f_i_l_e describe the map-
     pings 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 subse-
     quent 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.  _u_i_d_-_m_a_p_f_i_l_e should contain
     all uid mappings, and _g_i_d_-_m_a_p_f_i_l_e should contain all gid mappings.  Any
     uids not mapped in _u_i_d_-_m_a_p_f_i_l_e will be treated as user NOBODY, and any
     gids not mapped in _g_i_d_-_m_a_p_f_i_l_e 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.

     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.  mmoouunntt__uummaapp
     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.

     The layer created by the mmoouunntt__uummaapp 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.

SSEEEE AALLSSOO
     mount_null(8),  mount_lofs(8)

HHIISSTTOORRYY
     The mmoouunntt__uummaapp utility first appeared in 4.4BSD.

4.4BSD                           June 9, 1993                                1