dfm(4M)                        DG/UX R4.11MU05                       dfm(4M)


NAME
       dfm - DOS file manager

DESCRIPTION
       The DG/UX kernel provides support for PC DOS formatted floppies in 4
       different formats and partitioned hard disks.  There is support for
       the high and low density versions of the 5.25" and 3.5" floppy disk
       drives.  A high density 5.25" floppy holds 1.2 megabytes while a low
       density 5.25" floppy holds 360kb.  A high density 3.5" floppy holds
       1.4 megabytes while a low density one holds 720kb.  The partitioned
       hard disk support will work with most SCSI DOS partitioned disks.
       Multiple partitions from the same hard disk may be mounted
       simultaneously.

       The DOS file manager allows the system administrator to mount a DOS
       file system into the UNIX file system hierarchy.  A mounted DOS file
       system will appear as a UNIX file system with some restrictions
       imposed by the DOS file system structure.  There are only two basic
       file types supported in this file system, ordinary files and
       directories.  Hidden and system files will be displayed, but cannot
       be created.  The mode of all files from the DOS file system will be
       read/write and executable for user, group and other.  This will be
       true even if the floppy is mounted readonly or rendered readonly in a
       physical manner.  However, you will not be able to modify such a
       floppy.  Attempting to will result in an error.  Also, if you try to
       mount a file system for read/write that is physically marked
       readonly, you will get an error from the system.

       In DOS, there is a restriction on the names of files and directories.
       DOS filenames come from a more restrictive character set than normal
       DG/UX filenames.  First, there is no case sensitivity in DOS
       filenames.  The DOS file manager will translate all input filenames
       to upper case for storage on the floppy, and display all filename
       characters found on the floppy as lower case when outputting them to
       the user.  Secondly, names on the DOS file system are restricted to
       two naming components, a base component of 8 characters, and an
       extension component of 3 characters.  The DOS file manager will
       display this multiple component name with a period character between
       them, since period is an illegal filename character in a DOS filename
       and this follows the naming convention used in DOS when specifying
       filenames.

       The DOS file system is a convenient interchange mechanism when a
       network is not available.  It is not intended to be a high
       performance file system.  Not all of the DG/UX system calls will
       operate on files from the DOS file system.  They will return the
       errno EOPNOTSUPP if they do not operation on DOS files.  These will
       be calls such as link, readlink, symlink, file locking calls, chmod,
       chown, chgrp, dgunbufferedwrite, and dgunbufferedread.

       DOS filesystems are exportable over NFS.  However, filehandles may be
       invalidated in more cases (rename, server crash) than they are when
       using a normal dg/ux file system.  For the most consistent usage, it
       is recommended that you export them readonly.

       If you remove a floppy from the drive before you unmount the floppy,
       you will get inconsistent results.  You can, however, unmount the
       floppy without the floppy being present.

       If a physically write protected floppy is the subject of a read/write
       mount, the error ENXIO (no such device or address) results.

       To mount a DOS floppy:

            mount -t dos /dev/pdsk/4 /pdd/floppy

       The special device mentioned in the mount command is the block
       special representation of the floppy device in /dev/pdsk.  The type
       "dos" must be used with mount to route the mount request to the
       correct file manager.

       To mount a DOS hard disk partition:

            mount -t dos /dev/pdsk/4:c /pdd/harddisk

       The special device in this mount line has the added :c, which
       specifies the DOS partition to mount, using "c" as the first
       partition.  Partitions c-z are supported.  If you don't specify the
       partition, the default is to mount the first one found on the hard
       disk.

       You may add a line to the /etc/fstab file to have the mount occur
       when the system is brought up to init level 3.

       /dev/pdsk/4    /pdd/floppy    dos rw x 0

       /dev/pdsk/4:c   /pdd/harddisk  dos rw x 0

       The umount(1M) command may be used to unmount the DOS floppy from the
       file system hierarchy

            umount /pdd/floppy

            umount /pdd/harddisk

       You can create DOS formatted floppies (but not partitioned hard
       disks) with the mkfs(1M) command:

            mkfs 720kb /dev/rpdsk/4

SEE ALSO
       mkfs(1M), mount(1M), umount(1M), config(1M), fstab(4).


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