dfm(4) DG/UX 5.4.2 dfm(4)
NAME
dfm - DOS file manager
DESCRIPTION
The DG/UX kernel provides configurable support for PC DOS formatted
floppies in 4 different formats. 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 DOS file manager allows the system administrator to mount a DOS
floppy into the UNIX file system hierarchy. A mounted DOS floppy
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.
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 outputing 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, dg_unbuffered_write and dg_unbuffered_read.
DOS filesystems are not exportable over NFS.
If you remove the floppy from the drive before you umount the floppy,
the system will prompt you for that floppy when you try to access the
floppy drive again. It will require you to put in the correct floppy
before allowing you access again. You can, however, umount the
floppy without the floppy being present.
In order to use the DOS file manager, you must configure the dfm()
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dfm(4) DG/UX 5.4.2 dfm(4)
pseudo device into your kernel.
sd(insc(),*)
st(insc(),*)
inen()
loop()
pmt()
prf()
meter()
dfm() # this is the line that must be added.
Once the kernel is built and running, you may use the mount(1M)
command to add the DOS floppy to the UNIX file system hierarchy.
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.
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
The umount(1M) command may be used to unmount the DOS floppy from the
file system hierarchy
umount /pdd/floppy
You can create DOS formatted floppies 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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