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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 4.10                     May 24, 1995                     FreeBSD 4.10

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

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