src/sbin/mount_msdos/mount_msdos.8

.\"	$OpenBSD: mount_msdos.8,v 1.33 2022/08/20 07:03:24 tb Exp $
.\"	$NetBSD: mount_msdos.8,v 1.10 1996/01/19 21:14:43 leo Exp $
.\"
.\" Copyright (c) 1993,1994 Christopher G. Demetriou
.\" All rights reserved.
.\"
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.\"      This product includes software developed by Christopher G. Demetriou.
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.Dd $Mdocdate: August 20 2022 $
.Dt MOUNT_MSDOS 8
.Os
.Sh NAME
.Nm mount_msdos
.Nd mount an MS-DOS file system
.Sh SYNOPSIS
.Nm mount_msdos
.Op Fl 9ls
.Op Fl g Ar group
.Op Fl m Ar mask
.Op Fl o Ar options
.Op Fl u Ar user
.Ar special
.Ar node
.Sh DESCRIPTION
The
.Nm
command attaches the MS-DOS file system residing on
the device
.Ar special
to the global file system namespace at the location
indicated by
.Ar node .
This command is invoked by
.Xr mount 8
when using the syntax
.Bd -ragged -offset 4n
.Nm mount Op options
-t msdos
.Ar special node
.Ed
.Pp
The
.Ar special
device must correspond to a partition registered in the
.Xr disklabel 5 .
.Pp
This command is normally executed by
.Xr mount 8
at boot time, but can be used by any user to mount an
MS-DOS file system on any directory that they own (provided,
of course, that they have appropriate access to the device that
contains the file system).
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl 9
Ignore the special Windows 95/98 directory entries even
if deleting or renaming a file.
This forces
.Fl s .
.It Fl g Ar group
Specifies the group name or GID of the root inode of the file system.
Defaults to the mount point's GID.
.It Fl l
Force listing and generation of
Windows 95/98 long filenames
and separate creation/modification/access dates.
.Pp
This is the default.
.It Fl m Ar mask
Specify the maximum permissions for files and directories
in the file system.
Only the nine low-order bits of
.Ar mask
are used.
.It Fl o Ar options
Use the specified mount
.Ar options ,
as described in
.Xr mount 8 .
.It Fl s
Force behaviour to
ignore and not generate Windows 95/98 long filenames.
.It Fl u Ar user
Specifies the user name or UID of the root inode of the file system.
Defaults to the mount point's UID.
.El
.Pp
File permissions for FAT file systems are imitated,
since the file system has no real concept of permissions.
The default mask is taken from the
directory on which the file system is being mounted,
except when the
.Fl m
option is used.
FAT does have a
.Dq read only
mode,
in which the writable bit is unset.
If such files are found,
they are marked non-writable;
it can be set using
.Li chmod -w
or unset using
.Li chmod +w .
.Pp
File modes work the same way for directories.
However a directory will inherit the executable bit if it is readable.
See
.Xr chmod 1
for more information about octal file modes.
.Sh SEE ALSO
.Xr chmod 1 ,
.Xr mount 2 ,
.Xr disklabel 5 ,
.Xr fstab 5 ,
.Xr disklabel 8 ,
.Xr mount 8 ,
.Xr umount 8
.Sh HISTORY
The
.Nm
utility first appeared in
.Nx 0.9 .
Its predecessor, the
.Nm mount_pcfs
utility, appeared in
.Nx 0.8 ,
and was abandoned in favor
of the more aptly named
.Nm mount_msdos .
.Sh AUTHORS
.An -nosplit
The original code was written by
.An Paul Popelka Aq Mt paulp@uts.amdahl.com
as a patch to
.Bx 386 0.1
in November 1992.
The current version is based on code written by
.An Christopher G. Demetriou Aq Mt cgd@netbsd.org
in April 1994.
.Sh CAVEATS
The maximum file size supported by the MS-DOS file system is
one byte less than 4GB.
This is a FAT file system limitation, documented by Microsoft
in Knowledge Base article 314463.
.Pp
The MS-DOS file system (even with long filenames) does not support
filenames with trailing dots or spaces.
Any such characters will be silently removed before the directory entry
is written.
This too is a FAT file system limitation.
.Pp
The use of the
.Fl 9
flag could result in damaged file systems,
albeit the damage is in part taken care of by
procedures similar to the ones used in Windows 95/98.
.Pp
Note that Windows 95/98 handles only access dates,
but not access times.