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 argument 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 exam-
     ple, 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