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From: terry@cs.weber.edu (A Wizard of Earth C)
Subject: Re: Questions about the file system!
Message-ID: <1993Mar23.023754.2570@fcom.cc.utah.edu>
Sender: news@fcom.cc.utah.edu
Organization: Weber State University (Ogden, UT)
References: <1oj38cINN9em@harpo.uccs.edu>
Date: Tue, 23 Mar 93 02:37:54 GMT
Lines: 60
In article <1oj38cINN9em@harpo.uccs.edu> jmward@elbert (Joel M. Ward) writes:
> What exactly is involved in writing a new filesystem? See, i am
>interested in writing a new fs that does on-the-fly data compresion.
>HOw's that for a lofty goal?
>
> Now if only i knew where to start.... Can anyone point me to any
>docs or anything?? And how much disk space do i need to compile a new fs?
Writing a new file system is fairly easy. Understanding it in the first
place is the difficult thing, since the documentation is basically the
source code and usenix papers.
You might try:
Beta document on writing file system types from Dell (requires SVR4 source
license):
UNIX (R) System V/386
Release 4 Version 3
Programmer's Guide:
Writing File
System Types
(From AT&T)
You may also want to look into:
Writing a Device Driver for AIX Version 3.2
IBM Publication Number GG24-3629-01
Chapter 9. Writing a Virtual File System
(Includes sample code on 3 1/2 disk for "demofs")
I have a rough manuscript done on this subject from a portability/SVR4
perspective, but it's far from distributable.
If you are serious about the compression, you may want to wait for 0.2; I
hear it uses much of the code that was used by BSD 4.4 (John Heidemann's
work at UCLA), so it is based on a stackable vnode interface. This
means the bottom layer has a strict definition (not true of the current
VFS interface) and it supports user space developement of code to go
into the kernel through a kernel/user connection module.
The disk space needed to *compile* your new fs is miniscule -- maybe another
3 meg on top of what you need to rebuild kernels in the first place; to
run it, you will need to use a floppy or you will need to reserve a partition
for the new fs, your choice.
Good Luck!
Terry Lambert
terry@icarus.weber.edu
terry_lambert@novell.com
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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