man(1) Manual page archive

     BIND(2)                                                   BIND(2)

          bind, mount, unmount - change name space

          int bind(char *name, char *old, int flag)

          int mount(int fd, char *old, int flag, char *aname, char

          int unmount(char *name, char *old)

          Bind and mount modify the file name space of the current
          process and other processes in its name space group (see
          fork(2)). For both calls, old is the name of an existing
          file or directory in the current name space where the modi-
          fication is to be made.  The name old is evaluated as
          described in intro(2), except that no translation of the
          final path element is done.

          For bind, name is the name of another (or possibly the same)
          existing file or directory in the current name space.  After
          a successful bind call, the file name old is an alias for
          the object originally named by name; if the modification
          doesn't hide it, name will also still refer to its original
          file.  The evaluation of new happens at the time of the
          bind, not when the binding is later used.

          The fd argument to mount is a file descriptor of an open
          network connection or pipe to a file server.  The old file
          must be a directory.  After a successful mount the file tree
          served (see below) by fd will be visible with its root
          directory having name old.

          The flag controls details of the modification made to the
          name space.  In the following, new refers to the file as
          defined by name or the root directory served by fd. Either
          both old and new files must be directories, or both must not
          be directories.  Flag can be one of:

          MREPL     Replace the old file by the new one.  Henceforth,
                    an evaluation of old will be translated to the new
                    file.  If they are directories (for mount, this
                    condition is true by definition), old becomes a
                    union directory consisting of one directory (the
                    new file).

          MBEFORE   Both the old and new files must be directories.
                    Add the constituent files of the new directory to
                    the union directory at old so its contents appear

     BIND(2)                                                   BIND(2)

                    first in the union.  After an MBEFORE bind or
                    mount, the new directory will be searched first
                    when evaluating file names in the union directory.

          MAFTER    Like MBEFORE but the new directory goes at the end
                    of the union.

          The flags are defined in <libc.h>.  In addition, there is an
          MCREATE flag that can be OR'd with any of the above.  When a
          create system call (see open(2)) attempts to create in a
          union directory, and the file does not exist, the elements
          of the union are searched in order until one is found with
          MCREATE set.  The file is created in that directory; if that
          attempt fails, the create fails.

          With mount, the file descriptor fd must be open for reading
          and writing and prepared to respond to 9P messages (see Sec-
          tion 5).  After the mount, the file tree starting at old is
          served by a kernel mnt(3) device.  That device will turn
          operations in the tree into messages on fd. Aname selects
          among different file trees on the server; the null string
          chooses the default tree.  Authserv is the textual name of
          the file server.  It is used during authentication to assure
          that fd is a connection to the intended server.  If authserv
          is the empty string, no authentication is performed and the
          empty string is used as the authentication key in the attach
          message (see auth(5) and attach(5)).

          The file descriptor fd is automatically closed by a success-
          ful mount call.

          The effects of bind and mount can be undone by unmount. If
          name is zero, everything bound to or mounted upon old is
          unbound or unmounted.  If name is not zero, it is evaluated
          as described above for bind, and the effect of binding or
          mounting that particular result on old is undone.

          bind(1), intro(2), fcall(2), intro(5), mnt(3), srv(3)

          These routines set errstr.

          Mount will not return until it has successfully attached to
          the file server, so the process doing a mount cannot be the
          one serving.