<commit_before>.\" Copyright (c) 1980, 1989, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)mount.2	8.3 (Berkeley) 5/24/95
.\" $FreeBSD$
.\"
.Dd May 24, 1995
.Dt MOUNT 2
.Os
.Sh NAME
.Nm mount ,
.Nm unmount
.Nd mount or dismount a file system
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft int
.Fn mount "const char *type" "const char *dir" "int flags" "void *data"
.Ft int
.Fn unmount "const char *dir" "int flags"
.Sh DESCRIPTION
The
.Fn mount
system call grafts
a file system object onto the system file tree
at the point
.Fa dir .
The argument
.Fa data
describes the file system object to be mounted.
The argument
.Fa type
tells the kernel how to interpret
.Fa data
(See
.Fa type
below).
The contents of the file system
become available through the new mount point
.Fa dir .
Any files in
.Fa 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.
.Pp
By default only the super-user may call the
.Fn mount
system call.
This restriction can be removed by setting the
.Va vfs.usermount
.Xr sysctl 8
variable
to a non-zero value.
.Pp
The following
.Fa flags
may be specified to
suppress default semantics which affect file system access.
.Bl -tag -width MNT_SYNCHRONOUS
.It Dv 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.
.It Dv MNT_NOEXEC
Do not allow files to be executed from the file system.
.It Dv MNT_NOSUID
Do not honor setuid or setgid bits on files when executing them.
This flag is set automatically when the caller is not the super-user.
.It Dv MNT_NOATIME
Disable update of file access times.
.It Dv MNT_NODEV
Do not interpret special files on the file system.
This flag is set automatically when the caller is not the super-user.
.It Dv MNT_SUIDDIR
Directories with the SUID bit set chown new files to their own owner.
.It Dv MNT_SYNCHRONOUS
All I/O to the file system should be done synchronously.
.It Dv MNT_ASYNC
All I/O to the file system should be done asynchronously.
.It Dv MNT_FORCE
Force a read-write mount even if the file system appears to be unclean.
Dangerous.
.It Dv MNT_NOCLUSTERR
Disable read clustering.
.It Dv MNT_NOCLUSTERW
Disable write clustering.
.El
.Pp
The flag
.Dv 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.
.Pp
The flag
.Dv MNT_RELOAD
causes the vfs subsystem to update its data structures pertaining to
the specified already mounted file system.
.Pp
The
.Fa type
argument names the file system.
The types of file systems known to the system can be obtained with
.Xr lsvfs 1 .
.Pp
The
.Fa data
argument
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
.Xr lsvfs 1 .
Thus the
.Tn NFS
file system is described by the
.Xr mount_nfs 8
manual page.
.Pp
The
.Fn unmount
system call disassociates the file system from the specified
mount point
.Fa dir .
.Pp
The
.Fa flags
argument may specify
.Dv 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.
.Pp
The
.Dv MNT_SUIDDIR
option requires the SUIDDIR option to have been compiled into the kernel
to have any effect.
See the
.Xr mount 8
and
.Xr chmod 2
pages for more information.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn mount
system call will fail when one of the following occurs:
.Bl -tag -width Er
.It Bq Er EPERM
The caller is neither the super-user nor the owner of
.Fa dir .
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or the entire length of a path name exceeded 1023 characters.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating a pathname.
.It Bq Er ENOENT
A component of
.Fa dir
does not exist.
.It Bq Er ENOTDIR
A component of
.Fa name
is not a directory,<commit_msg>Separate the description of the flags for mount(2) and unmount(2) to clarify which system call accepts which arguments. Previously the manual page gave the impression that calling unmount() with flags of (MNT_FORCE | MNT_UPDATE | MNT_RDONLY) would downgrade a read-write mount to read-only, which is clearly untrue; to do that, these flags should be passed to mount() instead.<commit_after>.\" Copyright (c) 1980, 1989, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)mount.2	8.3 (Berkeley) 5/24/95
.\" $FreeBSD$
.\"
.Dd June 30, 2003
.Dt MOUNT 2
.Os
.Sh NAME
.Nm mount ,
.Nm unmount
.Nd mount or dismount a file system
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/param.h
.In sys/mount.h
.Ft int
.Fn mount "const char *type" "const char *dir" "int flags" "void *data"
.Ft int
.Fn unmount "const char *dir" "int flags"
.Sh DESCRIPTION
The
.Fn mount
system call grafts
a file system object onto the system file tree
at the point
.Fa dir .
The argument
.Fa data
describes the file system object to be mounted.
The argument
.Fa type
tells the kernel how to interpret
.Fa data
(See
.Fa type
below).
The contents of the file system
become available through the new mount point
.Fa dir .
Any files in
.Fa 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.
.Pp
By default only the super-user may call the
.Fn mount
system call.
This restriction can be removed by setting the
.Va vfs.usermount
.Xr sysctl 8
variable
to a non-zero value.
.Pp
The following
.Fa flags
may be specified to
suppress default semantics which affect file system access.
.Bl -tag -width MNT_SYNCHRONOUS
.It Dv 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.
.It Dv MNT_NOEXEC
Do not allow files to be executed from the file system.
.It Dv MNT_NOSUID
Do not honor setuid or setgid bits on files when executing them.
This flag is set automatically when the caller is not the super-user.
.It Dv MNT_NOATIME
Disable update of file access times.
.It Dv MNT_NODEV
Do not interpret special files on the file system.
This flag is set automatically when the caller is not the super-user.
.It Dv MNT_SUIDDIR
Directories with the SUID bit set chown new files to their own owner.
This flag requires the SUIDDIR option to have been compiled into the kernel
to have any effect.
See the
.Xr mount 8
and
.Xr chmod 2
pages for more information.
.It Dv MNT_SYNCHRONOUS
All I/O to the file system should be done synchronously.
.It Dv MNT_ASYNC
All I/O to the file system should be done asynchronously.
.It Dv MNT_FORCE
Force a read-write mount even if the file system appears to be unclean.
Dangerous.
Together with
.Dv MNT_UPDATE
and
.Dv MNT_RDONLY ,
specify that the file system is to be forcibly downgraded to a read-only
mount even if some files are open for writing.
.It Dv MNT_NOCLUSTERR
Disable read clustering.
.It Dv MNT_NOCLUSTERW
Disable write clustering.
.El
.Pp
The flag
.Dv 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.
.Pp
The flag
.Dv MNT_RELOAD
causes the vfs subsystem to update its data structures pertaining to
the specified already mounted file system.
.Pp
The
.Fa type
argument names the file system.
The types of file systems known to the system can be obtained with
.Xr lsvfs 1 .
.Pp
The
.Fa data
argument
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
.Xr lsvfs 1 .
Thus the
.Tn NFS
file system is described by the
.Xr mount_nfs 8
manual page.
.Pp
The
.Fn unmount
system call disassociates the file system from the specified
mount point
.Fa dir .
.Pp
The
.Fa flags
argument may include
.Dv MNT_FORCE
to specify that the file system should be forcibly unmounted
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.
.Sh RETURN VALUES
.Rv -std
.Sh ERRORS
The
.Fn mount
system call will fail when one of the following occurs:
.Bl -tag -width Er
.It Bq Er EPERM
The caller is neither the super-user nor the owner of
.Fa dir .
.It Bq Er ENAMETOOLONG
A component of a pathname exceeded 255 characters,
or the entire length of a path name exceeded 1023 characters.
.It Bq Er ELOOP
Too many symbolic links were encountered in translating a pathname.
.It Bq Er ENOENT
A component of
.Fa dir
does not exist.
.It Bq Er ENOTDIR
A component of
.Fa name
is not a directory,
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