Path: utzoo!utgpu!watmath!clyde!att!lzaz!hutch
From: hutch@lzaz.ATT.COM (R.HUTCHISON)
Newsgroups: comp.unix.wizards
Subject: Re: questions about File System Switch
Message-ID: <320@lzaz.ATT.COM>
Date: 20 Dec 88 14:50:30 GMT
References: <352@siswat.UUCP>
Organization: AT&T ISL Lincroft NJ USA
Lines: 42

From article <352@siswat.UUCP>, by buck@siswat.UUCP (A. Lester Buck):
] I have seen a number of postings which have mentioned the
] File System Switch (FSS), and Bach has some general sections
] on file system abstractions.  Is FSS fully documented in
] some AT&T manual?  What release of System V introduced FSS?

I don't know of any manual but I do know it is described in some
detail in AT&T's UNIX System Internals courses.  The more detailed of
the two courses should give you about as much detail as you need to
write a new file system type.  FSS was introduced in SVR3.0.

] Is it always there, or is it a vendor option that can be
] left out?  (I only have S5R2 experience.)

It better always be there, since it is only the framework with which
to develop file system types.  The standard System V file system is
one of these file system types. 

] 
] Is adding a new filesystem on the same level as adding a
] device driver to the kernel? For example, can a binary site
] use some type of link kit to add filesystem routines without
] source code?

It is possible.  Actually the kernel work is not all that difficult
compared to all the work you have to do after the kernel work is
finished (your own mkfs, fsck, fsdb, etc...).

] Or is this a "Don't try this at home, kids!" operation?

I think its more like... try this only if you have a lot of spare time
and won't mind doing it again when SVR4 comes along.  Remember, FSS
was not officially documented in the SVID (or elsewhere); the courses
told you about it because they had the duty of describing the internal
workings of the OS - not to give delevlopment advice......

[ stuff deleted ]

] A. Lester Buck		...!uhnix1!moray!siswat!buck

Bob Hutchison
att!lzaz!hutch