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MOUNT(2)                    BSD System Calls Manual                   MOUNT(2)

NAME
     mount, unmount -- mount or dismount a filesystem

SYNOPSIS
     #include <sys/param.h>
     #include <sys/mount.h>

     int
     mount(const char *type, const char *dir, int flags, void *data);

     int
     unmount(const char *dir, int flags);

DESCRIPTION
     The mount() function grafts a filesystem object onto the system file tree at the point dir.  The argu-ment argument
     ment data describes the filesystem object to be mounted.  The argument type tells the kernel how to
     interpret data (See type below).  The contents of the filesystem become available through the new mount
     point dir.  Any files in dir at the time of a successful mount are swept under the carpet so to speak,
     and are unavailable until the filesystem is unmounted.

     The following flags may be specified to suppress default semantics which affect filesystem access.

     MNT_RDONLY       The filesystem should be treated as read-only; Even the super-user may not write on
                      it.

     MNT_NOEXEC       Do not allow files to be executed from the filesystem.

     MNT_NOSUID       Do not honor setuid or setgid bits on files when executing them.

     MNT_NODEV        Do not interpret special files on the filesystem.

     MNT_UNION        Union with underlying filesystem instead of obscuring it.

     MNT_SYNCHRONOUS  All I/O to the filesystem should be done synchronously.

     The flag MNT_UPDATE indicates that the mount command is being applied to an already mounted filesystem.
     This allows the mount flags to be changed without requiring that the filesystem be unmounted and
     remounted.  Some filesystems may not allow all flags to be changed.  For example, most filesystems will
     not allow a change from read-write to read-only.

     The flag MNT_RELOAD causes the vfs subsystem to update its data structures pertaining to the specified
     already mounted filesystem.

     The type argument defines the type of the filesystem.

     Data is a pointer to a structure that contains the type specific arguments to mount.  The format for
     these argument structures is described in the manual page for each filesystem.

     The umount() function call disassociates the filesystem from the specified mount point dir.

     The flags argument may specify MNT_FORCE to specify that the filesystem should be forcibly unmounted
     even if files are still active.  Active special devices continue to work, but any further accesses to
     any other active files result in errors even if the filesystem is later remounted.

RETURN VALUES
     The mount() returns the value 0 if the mount was successful, otherwise -1 is returned and the variable
     errno is set to indicate the error.

     Umount returns the value 0 if the umount succeeded; otherwise -1 is returned and the variable errno is
     set to indicate the error.

ERRORS
     Mount() will fail when one of the following occurs:

     [EPERM]         The caller is not the super-user, and the device-node and the mountpoint do not have
                     adequate ownership and permissions.

     [ENAMETOOLONG]  A component of a pathname exceeded {NAME_MAX} characters, or an entire path name
                     exceeded {PATH_MAX} characters.

     [ELOOP]         Too many symbolic links were encountered in translating a pathname.

     [ENOENT]        A component of dir does not exist.

     [ENOTDIR]       A component of name is not a directory, or a path prefix of special is not a directory.

     [EINVAL]        A pathname contains a character with the high-order bit set.

     [EBUSY]         Another process currently holds a reference to dir.

     [EFAULT]        Dir points outside the process's allocated address space.

     Umount may fail with one of the following errors:

     [EPERM]         The caller is not the super-user, and the mount() was not done by the user.

     [ENOTDIR]       A component of the path is not a directory.

     [EINVAL]        The pathname contains a character with the high-order bit set.

     [ENAMETOOLONG]  A component of a pathname exceeded {NAME_MAX} characters, or an entire path name
                     exceeded {PATH_MAX} characters.

     [ELOOP]         Too many symbolic links were encountered in translating the pathname.

     [EINVAL]        The requested directory is not in the mount table.

     [EBUSY]         A process is holding a reference to a file located on the filesystem.

     [EIO]           An I/O error occurred while writing cached filesystem information.

     [EFAULT]        Dir points outside the process's allocated address space.

SEE ALSO
     mount(8), umount(8)

BUGS
     Some of the error codes need translation to more obvious messages.

HISTORY
     Mount() and umount() function calls appeared in Version 6 AT&T UNIX.

4th Berkeley Distribution      December 11, 1993     4th Berkeley Distribution