327 lines
9.0 KiB
Groff
327 lines
9.0 KiB
Groff
.\" 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 8.3 (Berkeley) 5/24/95
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.\" $FreeBSD$
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.\"
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.Dd May 24, 1995
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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 unmount
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.Nd mount or dismount a filesystem
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.Sh LIBRARY
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.Lb libc
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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 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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Specifying MNT_UPDATE without this option will upgrade
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a read-only filesystem to read/write.
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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_NOATIME
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Disable update of file access times.
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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_SUIDDIR
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Directories with the SUID bit set chown new files to their own owner.
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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_ASYNC
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All I/O to the filesystem should be done asynchronously.
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.It Dv MNT_FORCE
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Force a read-write mount even if the filesystem appears to be unclean.
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Dangerous.
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.It Dv MNT_NOCLUSTERR
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Disable read clustering.
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.It Dv MNT_NOCLUSTERW
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Disable write clustering.
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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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many 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 names the filesystem.
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The types of filesystems known to the system can be obtained with
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.Xr lsvfs 1 .
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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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By convention filesystem manual pages are named
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by prefixing ``mount_'' to the name of the filesystem as returned by
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.Xr lsvfs 1 .
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Thus the
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.Nm NFS
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filesystem is described by the
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.Xr mount_nfs 8
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manual page.
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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 or made read-only
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(if MNT_UPDATE and MNT_RDONLY are also specified)
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even if files are 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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.Pp
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The
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.Dv MNT_SUIDDIR
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option requires the SUIDDIR option to have been compiled into the kernel
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to have any effect.
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See the
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.Xr mount 8
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and
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.Xr chmod 2
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pages for more information.
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.Sh RETURN VALUES
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The
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.Fn mount
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returns 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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The
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.Fn unmount
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function returns the value 0 if the umount 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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The
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.Fn mount
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function will fail when one of the following occurs:
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.Bl -tag -width Er
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.It Bq Er EPERM
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The caller is not the super-user.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or the entire length of a path name exceeded 1023 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 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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The following errors can occur for a
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.Em ufs
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filesystem mount:
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.Bl -tag -width Er
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.It Bq Er ENODEV
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A component of ufs_args
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.Ar fspec
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does not exist.
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.It Bq Er ENOTBLK
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.Ar Fspec
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is not a block device.
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.It Bq Er ENXIO
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The major device number of
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.Ar fspec
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is out of range (this indicates no device driver exists
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for the associated hardware).
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.It Bq Er EBUSY
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.Ar Fspec
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is already mounted.
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.It Bq Er EMFILE
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No space remains in the mount table.
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.It Bq Er EINVAL
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The super block for the filesystem had a bad magic
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number or an out of range block size.
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.It Bq Er ENOMEM
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Not enough memory was available to read the cylinder
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group information for the filesystem.
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.It Bq Er EIO
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An I/O error occurred while reading the super block or
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cylinder group information.
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.It Bq Er EFAULT
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.Ar Fspec
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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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The following errors can occur for a
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.Em nfs
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filesystem mount:
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.Bl -tag -width Er
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.It Bq Er ETIMEDOUT
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.Em Nfs
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timed out trying to contact the server.
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.It Bq Er EFAULT
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Some part of the information described by nfs_args
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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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The following errors can occur for a
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.Em mfs
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filesystem mount:
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.Bl -tag -width Er
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.It Bq Er EMFILE
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No space remains in the mount table.
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.It Bq Er EINVAL
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The super block for the filesystem had a bad magic
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number or an out of range block size.
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.It Bq Er ENOMEM
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Not enough memory was available to read the cylinder
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group information for the filesystem.
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.It Bq Er EIO
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A paging error occurred while reading the super block or
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cylinder group information.
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.It Bq Er EFAULT
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.Em Name
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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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The
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.Fn unmount
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function may fail with one of the following errors:
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.Bl -tag -width Er
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.It Bq Er EPERM
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The caller is not the super-user.
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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 ENAMETOOLONG
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A component of a pathname exceeded 255 characters,
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or an entire path name exceeded 1023 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 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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.Pp
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A
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.Em ufs
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or
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.Em mfs
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mount can also fail if the maximum number of filesystems are currently
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mounted.
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.Sh SEE ALSO
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.Xr lsvfs 1 ,
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.Xr mfs 8 ,
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.Xr mount 8 ,
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.Xr umount 8
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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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