254 lines
7.4 KiB
Groff
254 lines
7.4 KiB
Groff
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.\" $OpenBSD: mount.2,v 1.6 1997/03/09 19:41:16 millert Exp $
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.\" $NetBSD: mount.2,v 1.12 1996/02/29 23:47:48 jtc Exp $
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.\"
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.\" Copyright (c) 1980, 1989, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)mount.2 8.2 (Berkeley) 12/11/93
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.\"
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.Dd December 11, 1993
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.Dt MOUNT 2
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.Os BSD 4
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.Sh NAME
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.Nm mount ,
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.Nm fmount,
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.Nm unmount
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.Nd mount or dismount a filesystem
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.Sh SYNOPSIS
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.Fd #include <sys/param.h>
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.Fd #include <sys/mount.h>
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.Ft int
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.Fn mount "const char *type" "const char *dir" "int flags" "void *data"
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.Ft int
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.Fn fmount "const char *type" "int fd" "int flags" "void *data"
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.Ft int
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.Fn unmount "const char *dir" "int flags"
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.Sh DESCRIPTION
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The
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.Fn mount
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function grafts
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a filesystem object onto the system file tree
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at the point
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.Ar dir .
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The argument
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.Ar data
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describes the filesystem object to be mounted.
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The argument
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.Ar type
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tells the kernel how to interpret
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.Ar data
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(See
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.Ar type
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below).
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The contents of the filesystem
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become available through the new mount point
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.Ar dir .
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Any files in
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.Ar dir
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at the time
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of a successful mount are swept under the carpet so to speak, and
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are unavailable until the filesystem is unmounted.
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.Pp
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The following
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.Ar flags
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may be specified to
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suppress default semantics which affect filesystem access.
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.Bl -tag -width MNT_SYNCHRONOUS
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.It Dv MNT_RDONLY
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The filesystem should be treated as read-only;
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Even the super-user may not write on it.
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.It Dv MNT_NOEXEC
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Do not allow files to be executed from the filesystem.
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.It Dv MNT_NOSUID
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Do not honor setuid or setgid bits on files when executing them.
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.It Dv MNT_NODEV
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Do not interpret special files on the filesystem.
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.It Dv MNT_UNION
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Union with underlying filesystem instead of obscuring it.
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.It Dv MNT_SYNCHRONOUS
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All I/O to the filesystem should be done synchronously.
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.It Dv MNT_CPROTECT
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Enable data protection on the filesystem if the filesystem is configured for it.
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.El
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.Pp
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The flag
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.Dv MNT_UPDATE
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indicates that the mount command is being applied
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to an already mounted filesystem.
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This allows the mount flags to be changed without requiring
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that the filesystem be unmounted and remounted.
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Some filesystems may not allow all flags to be changed.
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For example,
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most filesystems will not allow a change from read-write to read-only.
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.Pp
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The flag
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.Dv MNT_RELOAD
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causes the vfs subsystem to update its data structures pertaining to
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the specified already mounted filesystem.
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.Pp
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The
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.Fa type
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argument defines the type of the filesystem.
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.Pp
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.Fa Data
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is a pointer to a structure that contains the type
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specific arguments to mount.
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The format for these argument structures is described in the
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manual page for each filesystem.
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.Pp
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The
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.Fn fmount
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function call is equivalent to the
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.Fn mount
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function call, except in the use of the second argument.
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It takes an open file descriptor representing mount point
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instead of the string literal containing full path to the mount
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point in the filesystem hierarchy.
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.Pp
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The
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.Fn unmount
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function call disassociates the filesystem from the specified
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mount point
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.Fa dir .
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.Pp
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The
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.Fa flags
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argument may specify
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.Dv MNT_FORCE
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to specify that the filesystem should be forcibly unmounted even if files are
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still active.
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Active special devices continue to work,
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but any further accesses to any other active files result in errors
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even if the filesystem is later remounted.
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.Sh RETURN VALUES
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The
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.Fn mount
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and
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.Fn fmount
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return the value 0 if the mount was successful, otherwise -1 is returned
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and the variable
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.Va errno
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is set to indicate the error.
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.Pp
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.Nm unmount
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returns the value 0 if the unmount succeeded; otherwise -1 is returned
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and the variable
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.Va errno
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is set to indicate the error.
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.Sh ERRORS
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.Fn mount
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and
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.Fn fmount
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will fail when one of the following occurs:
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.Bl -tag -width [ENAMETOOLONG]
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.It Bq Er EPERM
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The caller is not the super-user, and the device-node and the mountpoint
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do not have adequate ownership and permissions.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded
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.Dv {NAME_MAX}
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characters, or an entire path name exceeded
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.Dv {PATH_MAX}
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characters.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating a pathname.
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.It Bq Er ENOENT
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A component of
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.Fa dir
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does not exist.
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.It Bq Er ENOTDIR
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A component of
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.Ar name
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is not a directory,
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or a path prefix of
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.Ar special
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is not a directory.
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.It Bq Er EINVAL
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A pathname contains a character with the high-order bit set.
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.It Bq Er EBUSY
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Another process currently holds a reference to
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.Fa dir .
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.It Bq Er EFAULT
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.Fa Dir
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points outside the process's allocated address space.
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.El
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.Pp
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.Nm unmount
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may fail with one of the following errors:
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.Bl -tag -width [ENAMETOOLONG]
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.It Bq Er EPERM
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The caller is not the super-user, and the
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.Nm mount()
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was not done by the user.
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.It Bq Er EPERM
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A system policy denied the operation.
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.It Bq Er ENOTDIR
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A component of the path is not a directory.
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.It Bq Er EINVAL
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The pathname contains a character with the high-order bit set.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded
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.Dv {NAME_MAX}
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characters, or an entire path name exceeded
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.Dv {PATH_MAX}
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characters.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er ENOENT
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A component of
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.Fa dir
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does not exist.
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.It Bq Er EINVAL
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The requested directory is not in the mount table.
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.It Bq Er EBUSY
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A process is holding a reference to a file located
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on the filesystem.
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.It Bq Er EIO
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An I/O error occurred while writing cached filesystem information.
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.It Bq Er EFAULT
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.Fa Dir
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points outside the process's allocated address space.
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.El
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.Sh SEE ALSO
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.Xr mount 8 ,
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.Xr unmount 8 ,
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.Xr open 2
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.Sh BUGS
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Some of the error codes need translation to more obvious messages.
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.Sh HISTORY
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.Fn mount
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and
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.Fn unmount
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function calls appeared in
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.At v6 .
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.Fn fmount
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function call first appeared in macOS version 10.13.
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