FileMount V1.21



Copyright (C) 1993 by Dan Babcock

Freely redistributable for non-commercial purposes



Introduction



	FileMount is a simple utility designed to create what I call 
"pseudo-partitions". A pseudo-partition has all the characteristics of a real 
partition, but resides within a file. Now, this begs the question, "what is a 
partition"? On the Amiga a partition is simply a set of contiguous sectors on 
a disk. A file on the other hand is not required to comprise only contiguous 
sectors; each data block may reside anywhere on the disk. To bridge this 
gap various people have written device drivers that operate on files, for 
example FMS by Matt Dillon or FDEV by Timo Rossi. They do a good job, 
but have some disadvantages. For one, they are slow compared to a real 
partition. What's worse, though, is that you can't use them with AMAX, or 
other operating systems, because AmigaDOS won't be around to access 
the file.

	FileMount takes a different approach, creating a file composed of 
only contiguous blocks, which can then be used like a true partition. 
Compared to a "real" partition, you have a couple big advantages: you 
don't need to backup/partition/restore (although some steps may need to 
be taken if your hard drive is highly fragmented) and you can recover the 
space simply by deleting the file.



Limitations



	FileMount requires Kickstart 2.04 or higher.

	FileMount is designed for use on Fast File System (FFS) partitions 
*ONLY*. Trying to use it on a partition using some other file system WILL 
corrupt your data. So don't try it.



Changes



	V1.10 fixes a major flaw of 1.00: various important MountList 
parameters such as MaxTransfer are now inherited from the host partition, 
rather than being hard-coded into FileMount. This isn't important for AMAX, 
but is very important for FFS or CrossDOS usage.

	V1.20 works around a rather devastating bug in the Fast File 
System. FFS only observs the lower 16-bits of lowcyl/highcyl, and so if the 
pseudo-partition happened to start more than 32MB into the disk FFS 
would stomp over a random portion of the drive instead of the part 
specified by FileMount. In this version the pseudo-partition is always 
placed on a 128-block boundary, and the "BlocksPerTrack" is set to 128 
(except in the case of CrossDOS or when the highcyl is under 65536). This 
may, depending upon the situation, invalidate an AMAX partition created 
with an earlier version of FileMount. This is regrettable, but the change had 
to be made.

	V1.21 - Added "NoActivate" option.



Usage



	FileMount is usable from the CLI only. Type "filemount ?" to see the 
command line options. It has two modes of operation, CREATE and 
MOUNT.



CREATE:



	The CREATE option takes a filename for the pseudo-partition file 
that you wish to create. The name of the file (apart from the directory path) 
will be the device name when you use the MOUNT option (described 
below). Along with the filename, there is a mandatory SIZE parameter 
which specifies the size of the pseudo-partition in kilobytes. Examples:



To create an AMAX partition of 15MB:

	filemount create devs:amax size 15000

To create a CrossDOS partition of 5MB:

	filemount create devs:pcc size 5000



	Assuming everything proceeded successfully, you should see some 
information printed including the starting and ending block numbers of the 
pseudo-partition. If you wanted, you could use this information to construct 
a MountList entry or a mount file. Normally, however, you will want to use 
the automatic mounting facility of FileMount, in which case you don't have 
to worry about anything.

	If your hard drive is highly fragmented, you may lack sufficient 
contiguous space for the pseudo-partition. You might choose to run a disk 
defragmentation utility (heeding the warnings given elsewhere if you 
already have pseudo-partitions installed) or go through a backup/restore 
cycle.

	The file created with CREATE will be delete-protected for your 
safety. If you really want to delete it either use Workbench or the CLI's 
PROTECT command to enable deletion. After deleting the file, REBOOT 
YOUR SYSTEM IMMEDIATELY (the reason is, if you accidentally use the 
pseudo-partition that you just deleted, your main partition will be 
corrupted).



WARNING! The CREATE option operates at the device level and *IF* there 
is a bug in this code it would have the potential to corrupt your hard drive. 
On the other hand, if your hard drive does not validate successfully after 
using CREATE, it isn't necessarily the fault of this program - your hard 
drive may have been corrupt already without you knowing it. In fact, this 
happened to me during the development of FileMount: my hard drive was 
"corrupted" after running FileMount, and since the code was basically 
untested, I assumed a bug in FileMount. I later found out that FileMount 
had in fact worked perfectly but that my hard drive was corrupted 
beforehand due to an incorrect MountList for my AMAX partition.



As an aside, this utility has been around long enough that I consider it 
"safe"; however it is the nature of software to surprise the user (and 
programmer) at the most inopertune moment.



MOUNT:



	The mount option activates the pseudo-partition and makes it known 
to AmigaDOS. You should place the appropriate "filemount mount" 
commands in your startup-sequence or user-startup files to automatically 
mount the partitions each time you boot. (Note: FileMount is "pure" and you 
may want to make it temporarily resident if you need to mount multiple 
pseudo-partitions). The MOUNT option takes as its argument the 
path/name of the file that you created earlier with the CREATE option. The 
name of the mounted device will be the same as the filename (excluding 
the path, of course). You only have two options for mounting the file: either 
for Fast File System (FFS), which will also work for AMAX, or for 
CrossDOS (either the version supplied with 2.1/3.0 of the OS or V5 of the 
full commercial version). FFS is the default. If you want the partition 
mounted for use with CrossDOS/CrossPC, specify the CROSSDOS option. 
New for V1.21: There is a "NoActivate" option which mounts the device 
without starting the file system. This can be used to avoid unsightly icons 
on your Workbench (e.g. for your AMAX partition). The "NoActivate" option 
may also be useful with PCTask (last time I played with PCT it didn't 
understand how to deal with a CrossDOS-mounted partition). Examples:



To mount the file "devs:DH1" for FFS:

	filemount mount devs:dh1



To mount the file "devs:AMAX" for AMAX:

	filemount mount devs:amax noactivate



To mount the file "devs:PCC" for use with CrossDOS/CrossPC:

	filemount mount devs:pcc crossdos

IMPORTANT INFO: The CROSSDOS option always mounts the 
pseudo-partition with a DOSTYPE of "MSH". That tells CrossDOS that the 
pseudo-partition is an MS-DOS hard drive ("MSD" would indicate a floppy). 
Clearly then, you can't simulate an MS-DOS floppy (no big deal). Rather, it 
is intended for the use of CrossPC or PC-Task. You can not format the 
CrossDOS partition with the AmigaDOS Format command!!! (The 
AmigaDOS format will only format "MSD" devices because it can't do the 
job of FDISK). You must run the MS-DOS program FDISK under 
CrossPC/PC-Task to create a partition on your simulated MS-DOS hard 
drive, and then use the MS-DOS Format command (don't forget the /S 
option to install system files!) to format the MS-DOS hard drive partition. 
Then and only then will you be able to read from and write to the partition 
with CrossDOS. ALSO NOTE: The CrossDOS partition name MUST end in 
the letter "C"!!! (The last letter corresponds to the MS-DOS partition. 
FileMount only allows you to mount one MS-DOS partition per 
pseudo-partition, so the letter will always be "C").



	The MOUNT option automatically checks the file for integrity and will 
refuse to mount if the pseudo-partition has been corrupted (that is, if the file 
no longer comprises only contiguous blocks). This protects your main 
Amiga partition.



!!!WARNINGS!!!

!!!PLEASE READ!!!



	FileMount is a somewhat "dangerous" utility is the sense that it 
requires some responsibility from the user. Failing to adhere to these 
precautions can be hazardous to your data.

	First and foremost, any time you copy the pseudo-partition file 
somewhere (during a hard drive backup, for example), you should assume 
all the data in the partition (that is, in the backup of the partition) to be lost. 
Now, that's not to say that the data is impossible to restore, but it's 
inconvenient. (One method would be to create a new filemount partition of 
_exactly_ the same size and then COPY (normal CLI copy command) from 
the file that represents the restored partition to the fresh partition. I have 
not actually tried this however...)

	Using a disk defragmentation utility will (in many cases) corrupt the 
pseudo-partitions!

	It is safe to rename the pseudo-partition file.



The Author



	I can be reached at d6b@ecl.psu.edu.



	Other fine freeware software products by me:



	QMouse: A small multi-functional "mouse utility" with a unique set of 
features

	Hackdisk: A trackdisk.device replacement offering a verify option