mount.2

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)mount.2	2.1	3/10/87
.TH mount 2
.SH Name
mount, umount \- mount or unmount a file system
.SH Syntax
#include <sys/types.h>
.br
#include <sys/fs_types.h>
.PP
mount(\fIspecial, name, rwflag, type, options\fP)
.br
char *\fIspecial\fP, *\fIname\fP;
.br
int \fIrwflag\fP, \fItype\fP;
.br
char *\fIoptions\fP;
.PP
umount(\fIdev\fP)
.br
dev_t \fIdev\fP;
.SH Description
.NXB "mount system call (general)"
.NXB "file system" "mounting"
.NXB "file system" "removing"
.NXR "umount system call (general)"
.NXAM "mount system call (general)" "mount command (general)"
The
.PN mount
system call announces to the system that a file system has
been mounted on
special file,
.I special.
References to file
.I name
refer to
the root file on the newly mounted file system.
.PP
The 
.I special
argument is a pointer to a null-terminated string
containing the pathname of the file system being mounted.
.PP
The 
.I name
argument is a pointer to a null-terminated string containing the pathname
of the root file on the newly mounted file system.  The
.I name
must already exist and must be a directory.
Its old contents
are inaccessible while the file system
is mounted.
.PP
The
.I rwflag
argument is used to determine whether the file system can be written
on; if it is 0, the file system is writable, if nonzero, the file
system is write-protected.  Physically write-protected disks and
magnetic tape file systems must be mounted read-only.
The
.PN mount 
call also detects devices that are offline at
mount time and returns the appropriate error.
.PP
The 
.I type 
argument identifies the file system type that is being mounted.
The file system types are defined in the <fs_types.h> file.
.PP
The 
.I options 
argument specifies certain parameters that can be used to define how
the file system is to be mounted.
.PP
The 
.I dev
argument to 
.PN umount
is the device id and
identifies the device that contains the file system that is to
be unmounted.
.SH Environment
.SS System V
The \fItype\fR and the \fIoptions\fR arguments are not available 
in the System V environment.
.PP
.NXR "mount system call (general)" "System V and"
Programs compiled in the System V environment cause
.PN mount 
and
.PN umount
to set errno to
ENOTDIR, instead of EPERM (illegal char in directory name) or EROFS (directory on
read  only  filesystem). If the process is not the superuser, errno is
set to EPERM, instead of ENODEV, and if the file does not exist, errno
is set to ENOENT, instead of ENODEV.
.PP
Also in the System V environment, only the low-order bit of
.I rwflag
is checked to determine write permission.
.PP
In the System V environment the syntax for 
.PN umount 
is as follows:
.RS 5
umount(\fIname\fR)
char *\fIname\fR;
.RE
.PP
The argument to 
.PN umount 
specifies the file system to be unmounted.  
In System V mode, the argument is the 
.PN name 
of the
device that contains the file system that is to be unmounted; 
in all other modes, it is the device id.
.SH Return Values
The
.PN mount
system call returns 0 upon successful completion of a mount operation;
it returns \-1 if the mount operation fails.
.PP
The
.PN umount
system call
announces to the system that the device
.I dev
no longer contains a file system.
The associated directory reverts to its ordinary interpretation.
.PP
The
.PN umount
system call
returns 0 if the dismount operation succeeds; \-1 if it fails.
.SH Diagnostics
.NXR "mount system call (general)" "diagnostics"
The
.PN mount
call fails under the following conditions:
.TP 15
[EPERM]
The caller is not the superuser.
.TP 15
[ENODEV]
A component
of
.I special
does not exist or the device is offline.
.TP 15
[ENOTBLK]
The
.I special
is not a block device.
.TP 15
[ENXIO]
The major device number of 
.I special
is out of range (indicating that no device driver exists
for the associated hardware).
.TP 15
[EINVAL]
The file system type is out of range.
.TP 15
[EINVAL]
The super block for the file system had a bad magic number or an
out-or-range block size.
.TP 15
[EINVAL]
The file system has not been unmounted cleanly, and the force option 
has not been set.
.TP 15
[ENOTDIR]
A component of
.I name
is not a directory,
or a path prefix of
.I special
is already mounted.
.TP 15
[EBUSY]
Another process currently holds a reference to
.IR name ,
or
.I special
is already mounted.
.TP 15
[ENAMETOOLONG]
A component of either pathname exceeded 255 characters,
or the entire length of either pathname exceeded 1023
characters.
.TP 15
[ELOOP]
Too many symbolic links were encountered in translating
either pathname.
.TP 15
[ENOENT]
A component of
.I name
does not exist.
.TP 15
[EMFILE]
No space remains in the mount table.
.TP 15
[ENOMEM]
Not enough memory was available to read the cylinder
group information for the file system.
.TP 15
[EIO]
An I/O error occurred while reading the super block or
cylinder group information.
.TP 15
[EFAULT]
The
.I special
or
.I name
points outside the process's allocated address space space.
.TP 15
[EROFS]
The
.I special
is a write-locked device and the user did not set the
.I rwflag.
.PP
The
.PN umount
command fails under the following conditions:
.TP 15
[EPERM]
The caller is not the superuser.
.TP 15
[EINVAL]
The requested device is not in the mount table.
.TP 15
[EBUSY]
A process is holding a reference to a file located
on the file system.
.TP 15
[EIO]
An I/O error occurred while writing the super block or other
cached file system information.
.TP 15
[EREMOTE]
An attempt has been made to mount an NFS remote file system that
is not local to the specified server.  This cannot
occur except in response to a failed 
.MS mount 2 .
.TP
[ETIMEDOUT]
A connect request or remote file operation failed
because the connected party
did not properly respond after a period
of time that is dependent on the communications protocol.
.SH See Also
mount(2nfs), mount(8), umount(8)
.NXE "mount system call (general)"
.NXE "file system" "mounting"
.NXE "file system" "removing"