FAT (mini) HOWTO

FAT (mini) HOWTO

        If there are any questions or comments, please direct them to
walt@erudition.net. The newest copy of this How-To can always be retrieved
from www.erudition.net/freebsd/. All rights for the reproduction of this
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	This mini HowTo deals with mounting DOS Floppies and
FAT16/FAT32/VFAT HardDisks in FreeBSD, and includes a quick section on the
background for partitioning schemes in x86 systems.


        1.      Background - HardDisk Partitions
        2.      Usage
	        2.1.    Mounting DOS HardDisks
        	2.2.    Mounting DOS Floppy Disks 

        3.      Appendix


	1.	Background

	Keep in mind that the following applies not only to FAT16, but
also FAT32 and VFAT. In the name of expediency, the term 'DOS' is used as
a catch-all to denote all of them.

	1.1.	HardDisk Partitions

	Without knowledge of the basic partition strategy on
DOS/Windows/Linux/BSD - x86 OSes in general - one is often left somewhat
confused when it comes to mounting DOS partitions in FreeBSD. These
restrictions are ancient, and contigent upon the BIOS structure found in
all x86 systems.

	DOS primary partitions are limited to a maximum of four. DOS
extended partitions, a method for allowing additional partitions, can
number higher, and allow one to design a system with more than four
partitions, however, these extended DOS partitions are not bootable.

 	FreeBSD on x86 systems suffers from the same limitation of four
primary partitions; however, in FreeBSD parlance, the 'parimary
partitions' are the 'slices' 1 - 4; in addition, in FreeBSD parlance, the
*working* equivalent of DOS 'extended partitions' are called 'partitions.'
That is, FreeBSD 'partitions' in FreeBSD perform the same task as DOS
'extended partitions' in DOS. This difference in terminology often
confuses newcomers to FreeBSD. To further confuse newcomers, DOS extended
partitions, as well as primary partitions, are recognized as slices under
FreeBSD. Although, FreeBSD is limited to 4 bootable FreeBSD slices, it can
mount more than four slices, be they FreeBSD slices, or slices
corresponding to other OS partitioning schemes. In this manner, FreeBSD is
far more flexible.

	2.	Usage

	As mentioned previously, DOS primary and extended partitions are
recognized as slices in FreeBSD. The primary partitions correspond to
slices numbering 1 through 4, while the extended partitions start at slice
5. For instance, if one has a DOS drive with a single primary partition,
and 4 extended partitions, the single primary partition would be
referenced by slice 1 in FreeBSD, and the 4 extended partitions would be
referenced by slices 5, 6, 7, and 8 in FreeBSD.

	Presuming that the DOS partitions existed on a common IDE drive,
and this was the first drive in the system, then the following table
illustrates the corresponding device file for each DOS partition:

	DOS Partitions	      |	FreeBSD Slices
	1st DOS Primary		/dev/wd0s1
	1st DOS Extended	/dev/wd0s5
	2nd "		"	/dev/wd0s6
	3rd "		"	/dev/wd0s7
	4th "		"	/dev/wd0s8

	2.1.	Mounting DOS HardDisks

	Understanding the concepts introduced in the previous sections,
the syntax required for mounting DOS partitions should not be alien. To
specify that one is mounting a DOS partition the 'msdos' parameter needs
to be specified with the -t option. For instance, if one is mounting the
first extended partition of a DOS drive, which is the second drive on the
system, on the mount point '/mnt/dos/' then the following command will
accomplish this:

	(root@erudition)/mnt># mount -t msdos /dev/wd1s5 /mnt/dos

	2.2.	Mounting DOS Floppy Disks

	To mount a DOS floppy, the partition issues previously introduced
can be ignored. For instance, to mount a floppy disk, in the first floppy
drive, on the mount point '/mnt/floppy/' then the following command will

        (root@erudition)/mnt># mount -t msdos /dev/fd0 /mnt/flp

	3.	Appendix


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