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

NAME
     mount, unmount - mount or dismount a file system

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 file system object onto the system file
     tree at the point dir.  The argument data describes the file system
     object to be mounted.  The argument type tells the kernel how to
     interpret data (See type below).  The contents of the file system 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 file system is unmounted.

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

     MNT_RDONLY       The file system 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 file system
                      to read/write.

     MNT_NOEXEC       Do not allow files to be executed from the file system.

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

     MNT_NOATIME      Disable update of file access times.

     MNT_NODEV        Do not interpret special files on the file system.

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

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

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

     MNT_FORCE        Force a read-write mount even if the file system 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 file system.  This allows the mount flags to be
     changed without requiring that the file system be unmounted and
     remounted.  Some file systems may not allow all flags to be changed.  For
     example, many file systems 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 file system.

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

     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 file system.  By convention file
     system manual pages are named by prefixing ``mount_'' to the name of the
     file system as returned by lsvfs(1).  Thus the NFS file system is
     described by the mount_nfs(8) manual page.

     The unmount() function call disassociates the file system from the
     specified mount point dir.

     The flags argument may specify MNT_FORCE to specify that the file system
     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 file system 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 not the super-user.

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

     [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 file system 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 file system 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 file system.

     [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 file system 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 unmount() function may fail with one of the following errors:

     [EPERM]            The caller is not the super-user.

     [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
                        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 file system.

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

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

     A ufs mount can also fail if the maximum number of file systems are
     currently mounted.

SEE ALSO
     lsvfs(1), mount(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 11.0-PRERELEASE          May 24, 1995          FreeBSD 11.0-PRERELEASE

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

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