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MOUNT(2)		  FreeBSD System Calls Manual		      MOUNT(2)

NAME
     mount, unmount -- mount or	dismount a filesystem

LIBRARY
     Standard C	Library	(libc, -lc)

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 suc-
     cessful mount are swept under the carpet so to speak, and are unavailable
     until the filesystem is unmounted.

     By	default	only the super-user may	call the mount() function.  This
     restriction can be	removed	by setting the sysctl vfs.usermount to a non-
     zero value.

     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.  Specifying MNT_UPDATE
		      without this option will upgrade a read-only filesystem
		      to read/write.

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

     MNT_NOSUID	      Do not honor setuid or setgid bits on files when execut-
		      ing them.	 This flag is set automatically	when the
		      caller is	not the	super-user.

     MNT_NOATIME      Disable update of	file access times.

     MNT_NODEV	      Do not interpret special files on	the filesystem.	 This
		      flag is set automatically	when the caller	is not the
		      super-user.

     MNT_SUIDDIR      Directories with the SUID	bit set	chown new files	to
		      their own	owner.

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

     MNT_ASYNC	      All I/O to the filesystem	should be done asynchronously.

     MNT_FORCE	      Force a read-write mount even if the filesystem appears
		      to be unclean.  Dangerous.

     MNT_NOCLUSTERR   Disable read clustering.

     MNT_NOCLUSTERW   Disable write clustering.

     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, many
     filesystems will not allow	a change from read-write to read-only.

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

     The type argument names the filesystem.  The types	of filesystems known
     to	the system can be obtained with	lsvfs(1).

     Data is a pointer to a structure that contains the	type specific argu-
     ments to mount.  The format for these argument structures is described in
     the manual	page for each filesystem.  By convention filesystem manual
     pages are named by	prefixing ``mount_'' to	the name of the	filesystem as
     returned by lsvfs(1).  Thus the NFS filesystem is described by the
     mount_nfs(8) manual page.

     The unmount() function call disassociates the filesystem from the speci-
     fied mount	point dir.

     The flags argument	may specify MNT_FORCE to specify that the filesystem
     should be forcibly	unmounted or made read-only (if	MNT_UPDATE and
     MNT_RDONLY	are also specified) 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.

     The MNT_SUIDDIR option requires the SUIDDIR option	to have	been compiled
     into the kernel to	have any effect.  See the mount(8) and chmod(2)	pages
     for more information.

RETURN VALUES
     Upon successful completion, the value 0 is	returned; otherwise the
     value -1 is returned and the global variable errno	is set to indicate the
     error.

ERRORS
     The mount() function will fail when one of	the following occurs:

     [EPERM]		The caller is neither the super-user nor the owner of
			dir.

     [ENAMETOOLONG]	A component of a pathname exceeded 255 characters, or
			the entire length of a path name exceeded 1023 charac-
			ters.

     [ELOOP]		Too many symbolic links	were encountered in translat-
			ing a pathname.

     [ENOENT]		A component of dir does	not exist.

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

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

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

     The following errors can occur for	a ufs filesystem mount:

     [ENODEV]		A component of ufs_args	fspec does not exist.

     [ENOTBLK]		Fspec is not a block device.

     [ENXIO]		The major device number	of fspec is out	of range (this
			indicates no device driver exists for the associated
			hardware).

     [EBUSY]		Fspec is already mounted.

     [EMFILE]		No space remains in the	mount table.

     [EINVAL]		The super block	for the	filesystem had a bad magic
			number or an out of range block	size.

     [ENOMEM]		Not enough memory was available	to read	the cylinder
			group information for the filesystem.

     [EIO]		An I/O error occurred while reading the	super block or
			cylinder group information.

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

     The following errors can occur for	a nfs filesystem mount:

     [ETIMEDOUT]	Nfs timed out trying to	contact	the server.

     [EFAULT]		Some part of the information described by nfs_args
			points outside the process's allocated address space.

     The following errors can occur for	a mfs filesystem mount:

     [EMFILE]		No space remains in the	mount table.

     [EINVAL]		The super block	for the	filesystem had a bad magic
			number or an out of range block	size.

     [ENOMEM]		Not enough memory was available	to read	the cylinder
			group information for the filesystem.

     [EIO]		A paging error occurred	while reading the super	block
			or cylinder group information.

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

     The unmount() function may	fail with one of the following errors:

     [EPERM]		The caller is neither the super-user nor the user who
			issued the corresponding mount(2) call.

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

     [ENAMETOOLONG]	A component of a pathname exceeded 255 characters, or
			an entire path name exceeded 1023 characters.

     [ELOOP]		Too many symbolic links	were encountered in translat-
			ing 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.

     A ufs or mfs mount	can also fail if the maximum number of filesystems are
     currently mounted.

SEE ALSO
     lsvfs(1), mfs(8), mount(8), sysctl(8), umount(8)

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

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

FreeBSD	10.1			 May 24, 1995			  FreeBSD 10.1

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | BUGS | HISTORY

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