439 lines
12 KiB
Groff
439 lines
12 KiB
Groff
.\" $NetBSD: mount.2,v 1.48 2011/06/17 18:12:32 wiz 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. 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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.\"
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.Dd June 17, 2011
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.Dt MOUNT 2
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.Os
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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 file system
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/param.h
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.In 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" "size_t data_len"
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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 file system 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 file system object to be mounted, and is
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.Ar data_len
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bytes long.
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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 file system
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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 file system 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 file system access.
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.Bl -tag -width MNT_SYNCHRONOUS
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.It Dv MNT_RDONLY
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The file system 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_UNION
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Union with underlying filesystem instead of obscuring it.
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.It Dv MNT_HIDDEN
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Cause the
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.Xr df 1
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program, and perhaps others, to, by default,
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exclude this filesystem from its output.
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.It Dv MNT_NOEXEC
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Do not allow files to be executed from the file system.
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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 file system.
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.It Dv MNT_NOCOREDUMP
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Do not allow programs to dump core files on the file system.
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.It Dv MNT_NOATIME
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Never update access time in the file system.
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.It Dv MNT_NODEVMTIME
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Never update modification time of device files.
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.It Dv MNT_SYMPERM
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Recognize the permission of symbolic link when reading or traversing.
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.It Dv MNT_SYNCHRONOUS
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All I/O to the file system should be done synchronously.
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This will slow I/O performance considerably, but
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enhances overall filesystem reliability.
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.It Dv MNT_ASYNC
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All I/O to the file system should be done asynchronously.
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This vastly improves I/O throughput,
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but at a cost of making the filesystem likely to be
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completely unrecoverable should the system crash while
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unwritten data is pending in kernel buffers.
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.It Dv MNT_LOG
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Use a filesystem journal.
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.Dv MNT_LOG
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causes a journal (or log) to be created in the
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filesystem, creating a record of meta-data writes to be
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performed, allowing the actual writes to be deferred.
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This improves performance in most cases.
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.It MNT_EXTATTR
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Enable extended attributes, if the filesystem supports them and
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does not enable them by default.
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Currently this is only the case for UFS1.
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.El
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.Pp
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The
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.Dv MNT_UPDATE ,
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.Dv MNT_RELOAD ,
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and
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.Dv MNT_GETARGS
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flags indicate that the mount command is being applied
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to an already mounted file system.
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The
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.Dv MNT_UPDATE
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flag allows the mount flags to be changed without requiring
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that the file system be unmounted and remounted.
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A conversion from read-write to read-only will fail if any files
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are currently open for writing on the filesystem, unless the
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.Dv MNT_FORCE
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flag is also applied.
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Some file systems may not allow all flags to be changed.
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For example,
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some file systems will not allow a change from read-write to read-only.
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The
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.Dv MNT_RELOAD
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flag causes kernel filesystem data to be reloaded from
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the filesystem device.
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It is only permitted on filesystems mounted read-only.
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Its purpose is to notify the system that the filesystem
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data has been modified by some external process.
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The
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.Dv MNT_GETARGS
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flag does not alter any of the mounted filesystem's properties,
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but returns the filesystem-specific arguments for the currently mounted
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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 file system.
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The types of file systems known to the system are defined in
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.In sys/mount.h ,
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and those supported by the current running kernel obtained
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using
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.Xr sysctl 8
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to obtain the node
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.\" .Bd -literal -offset indent
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vfs.generic.fstypes.
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.\" XXX from lite-2:
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.\" The types of filesystems known to the system can be obtained with
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.\" .Xr sysctl 8
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.\" by using the command:
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.\" .Bd -literal -offset indent
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.\" sysctl vfs
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.\" .Ed
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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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Some of the currently supported types of file systems and
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their type specific data are:
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.Pp
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.Dv MOUNT_FFS
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.Bd -literal -offset indent -compact
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struct ufs_args {
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char *fspec; /* block special file to mount */
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};
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.Ed
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.Pp
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.Dv MOUNT_NFS
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.Bd -literal -offset indent -compact
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struct nfs_args {
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int version; /* args structure version */
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struct sockaddr *addr; /* file server address */
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int addrlen; /* length of address */
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int sotype; /* Socket type */
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int proto; /* and Protocol */
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u_char *fh; /* File handle to be mounted */
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int fhsize; /* Size, in bytes, of fh */
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int flags; /* flags */
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int wsize; /* write size in bytes */
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int rsize; /* read size in bytes */
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int readdirsize; /* readdir size in bytes */
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int timeo; /* initial timeout in .1 secs */
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int retrans; /* times to retry send */
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int maxgrouplist; /* Max. size of group list */
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int readahead; /* # of blocks to readahead */
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int leaseterm; /* Term (sec) of lease */
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int deadthresh; /* Retrans threshold */
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char *hostname; /* server's name */
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};
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.Ed
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.Pp
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.Dv MOUNT_MFS
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.Bd -literal -offset indent -compact
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struct mfs_args {
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char *fspec; /* name to export for statfs */
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struct export_args30 pad; /* unused */
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caddr_t base; /* base of file system in mem */
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u_long size; /* size of file system */
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};
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.Ed
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.\" XXX from lite-2:
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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 sysctl 8 .
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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 file system 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 file system 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 file system is later remounted.
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.Sh RETURN VALUES
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.Fn mount
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returns the value 0 if the mount was successful,
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the number of bytes written to
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.Ar data
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for
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.Dv MNT_GETARGS ,
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otherwise \-1 is returned 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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.Fn 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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will fail when one of the following occurs:
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.Bl -tag -width Er
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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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or for an update from read-write to read-only
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there are files on the filesystem open for writes.
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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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.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 ENAMETOOLONG
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A component of a pathname exceeded
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.Brq Dv NAME_MAX
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characters, or an entire path name exceeded
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.Brq Dv PATH_MAX
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characters.
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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 EPERM
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The caller is not the super-user,
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and ordinary user mounts are not permitted or
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this particular request violates the rules.
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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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file system mount:
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.Bl -tag -width Er
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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 EFAULT
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.Ar Fspec
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points outside the process's allocated address space.
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.It Bq Er EINVAL
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The super block for the file system had a bad magic
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number or an out of range block size.
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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 EMFILE
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No space remains in the mount table.
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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 ENOMEM
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Not enough memory was available to read the cylinder
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group information for the file system.
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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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.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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file system mount:
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.Bl -tag -width Er
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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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.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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.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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file system mount:
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.Bl -tag -width Er
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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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.It Bq Er EINVAL
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The super block for the file system had a bad magic
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number or an out of range block size.
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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 EMFILE
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No space remains in the mount table.
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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 file system.
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.El
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.Pp
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.Fn unmount
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may fail with one of the following errors:
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.Bl -tag -width Er
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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 file system.
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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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.It Bq Er EINVAL
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The requested directory is not in the mount table.
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.It Bq Er EIO
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An I/O error occurred while writing cached file system information.
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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 ENAMETOOLONG
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A component of a pathname exceeded
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.Brq Dv NAME_MAX
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characters, or an entire path name exceeded
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.Brq Dv PATH_MAX
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characters.
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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 EPERM
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The caller is not the super-user.
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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 file systems are currently
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mounted.
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.Sh SEE ALSO
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.Xr df 1 ,
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.Xr getvfsstat 2 ,
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.Xr nfssvc 2 ,
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.Xr getmntinfo 3 ,
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.Xr symlink 7 ,
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.Xr mount 8 ,
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.Xr sysctl 8 ,
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.Xr umount 8
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.Sh HISTORY
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The
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.Fn mount
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and
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.Fn umount
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(now
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.Fn unmount )
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function calls were all present in
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.At v6 .
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.Pp
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Prior to
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.Nx 4.0
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the
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.Nm
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call was used to export NFS filesystems.
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This is now done through
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.Fn nfssvc .
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.Pp
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The
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.Dv data_len
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argument was added for
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.Nx 5.0 .
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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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.Pp
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Far more filesystems are supported than those those listed.
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