Add README

README.md

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-## PartFS: A FUSE filesystem for accessing part of a file. ##
+## Introduction ##
 
-PartFS is an in-development filesystem that lets a user mount a part of a file
-as a virtual file, with a user-specified offset and length.
+PartFS is a FUSE-based tool for accessing a chunk of a SOURCE file as if it
+were a separate file at MOUNTPOINT. It's intended for use in
+creating/modifying disk image files.
 
-This allows a user to access a single partition in a larger disk image, as
-well as other similar tasks.
+Say that SOURCE was a 600000-byte file with the following layout:
 
-PartFS is a work in progress. Expect to see changes added soon.
+    [Region 1] Bytes 1 to 5000: Bootloader region
+    [Region 2] Bytes 5001 to 105000: System data
+    [Region 3] Bytes 105001 to 205000: System Partition
+    [Region 4] Bytes 205001 to 600000: User Data
+
+PartFS would allow you to mount any of these regions and access them as if
+they were standalone files. In the example given above, the correct mounting
+parameters would be:
+
+    partfs SOURCE MOUNTPOINT -o offset=0,sizelimit=5000
+    partfs SOURCE MOUNTPOINT -o offset=5000,sizelimit=100000
+    partfs SOURCE MOUNTPOINT -o offset=105000,sizelimit=100000
+    partfs SOURCE MOUNTPOINT -o offset=205000,sizelimit=395000
+
+Note that region 1 could also be mounted with no offset because it starts at
+byte 0. Similarly, Region 4 could be mounted with no size-limit because it
+goes to the end of the file.
+
+PartFS is logically similar to a loopback-mounted image under Linux. It has
+two key differences though. First, it can be done as an unprivileged user.
+And second, it doesn't offer direct access to any filesystems stored 
+within the mounted image. Consider using with fuse2fs or a similar tool 
+or unprivileged filesystem access.
+
+## Current Status ##
+
+At the time of this writing, PartFS is released as version 1.0 with a functional
+test suite. There are no currently-known bugs. Use with pride.
+
+## License ##
+
+PartFS is proudly released under GPL 2.0.