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Path: utzoo!mnetor!seismo!ll-xn!ames!necntc!ncoast!allbery
From: mouse@mcgill-vision.UUCP (der Mouse )
Newsgroups: comp.sources.misc
Subject: filedisk: make a file into a filesystem (1 of 2) (BSD4.3)
Message-ID: <2741@ncoast.UUCP>
Date: Mon, 29-Jun-87 20:09:44 EDT
Article-I.D.: ncoast.2741
Posted: Mon Jun 29 20:09:44 1987
Date-Received: Wed, 1-Jul-87 03:43:38 EDT
Sender: allbery@ncoast.UUCP
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Approved: allbery@ncoast.UUCP
X-Archive: comp.sources.misc/8706/8


[Comment on the below:  it sure as heck isn't seismo, so it must be sun.
I try to avoid that site anyway, as the cwruecmp!sun link has been marked
DEAD in cwruecmp's map for quite a while now.  ++bsa]

This is part 1 of 2.  Read the README (first thing in the archive) to
see what it's part 1 of.  I had to split up even this tiny thing
because someone, either sun or seismo (not sure which), has a 10000
byte limit on mail (yes, only ten thousand bytes).
					der Mouse

				(mouse@mcgill-vision.uucp)

#! /bin/sh
#
# Shar: Shell Archiver
#
# This archive created Sun Jun 28 17:50:43 1987
# Run this through sh to create:
#	README
echo x - README \(5589 characters\)
sed 's/^X//' > README << \SHAR_EOF
Xfiledisk: a pseudo disk driver for UNIX.  This driver makes a normal
X	file look like a filesystem volume.
X
X	Currently in use on 4.3BSD.  Originally developed on 4.2BSD,
X	but the 4.2 version is buried in the mists of the past, so all
X	this says is that it won't take much to make it work on 4.2.  I
X	have attempted to use a somewhat modified version of this under
X	mtXinu 4.3+NFS but unfortunately it keeps crashing the system
X	for reasons yet to be discovered.  I haven't dared even try to
X	make it work on a Sun.  I won't, either, until we get source.
X
XYou should have received:
X
X	- README (this file)
X	- filedisk.c
X	- fdconn.c
X	- fddisc.c
X
XYou will need to:
X
X	- Put filedisk.c somewhere; I'll assume it's in
X	   ../local/filedisk.c (that's where we have it).  If you put
X	   it somewhere else, change the filename in the next item to
X	   point to wherever you did put it.
X
X	- Put a line
Xlocal/filedisk.c	optional memdisk
X	   in ../conf/files.YOURSYSTEMNAME.  For example, our
X	   configuration is in ../conf/LARRY and the kernel is built in
X	   ../LARRY; the file with the above line is then
X	   ../conf/files.LARRY (clear enough?).
X
X	- Put a line
Xpseudo-device	filedisk	1
X	   in ../conf/YOURSYSTEMNAME.  The 1 specifies how many pseudo
X	   disk devices you want to configure in; you may want to
X	   increase it.
X
X	- Edit conf.c.  This file is in ../vax for VAX and MicroVAX
X	   configurations and seems to be in ../sun (rather than
X	   ../machine, which is a link to sun2 or sun3 depending on
X	   which sort of Sun you have) for Suns.  You will need to
X	   insert the following, somewhere early (before both cdevsw[]
X	   and bdevsw[]).
X#include "filedisk.h"
X#if NFILEDISK > 0
Xextern int filediskopen();
Xextern int filediskstrategy();
Xextern int filediskread();
Xextern int filediskwrite();
Xextern int filediskioctl();
Xextern int filedisksize();
X#else
X#define filediskopen nodev
X#define filediskstrategy nodev
X#define filediskread nodev
X#define filediskwrite nodev
X#define filediskioctl nodev
X#define filedisksize nodev
X#endif
X	   Now you need to add a device to each of bdevsw[] and
X	   cdevsw[].  The bdevsw entry should look like
X	{ filediskopen,	nulldev,	filediskstrategy,nodev,		/* 10 */
X	  filedisksize,	0 },
X	   (the 10 should be changed to whatever number you choose to
X	   put it at).  The cdevsw entry should look like
X	filediskopen,	nulldev,	filediskread,	filediskwrite,	/* 34 */
X	filediskioctl,	nulldev,	nulldev,	0,
X	seltrue,	0,
X	   again, with the 34 changed to whatever is appropriate.
X
X	- add two #define lines to ../h/ioctl.h:
X#define LIOC_FSF_SET	_IOW(l,1,char *)		/* setup filedisk */
X#define LIOC_FSF_CLEAR	_IO(l,2)			/* clear filedisk */
X
XYou can now re-run config and rebuild your kernel.
X
XIf I haven't forgotten anything (:-), it should run fine.  Test the new
Xkernel.  When you are satisfied that adding the filedisk driver hasn't
Xbroken anything else, you can try it out:
X
X	- Create entries in /dev.  We use /dev/filedisk0 and
X	   /dev/rfiledisk0 (just 0 since we have just one configured
X	   in; if we had two, they'd be filedisk0/rfiledisk0 and
X	   filedisk1/rfiledisk1).
X
X	- Compile fdconn.c and fddisc.c; put the binaries wherever you
X	   feel appropriate.  As with any disk drive, the /dev entries
X	   should be mode xx0, probably mode 600 is best, unless you
X	   wouldn't mind entrusting all your users with your root
X	   password.  Fdconn and fddisc must be able to open the raw
X	   device /dev/rfiledisk0 (or rfiledisk1, or 2, or...) in order
X	   to function.
X
XNow to test it.  I should explain what fdconn and fddisc do.  Fdconn
Xconnects a pseudo-disk unit to a file; fddisc breaks the connection
Xcreated by fdconn.  A pseudo-disk unit must be connected to a file
Xbefore it can do anything useful, of course.
X
XLet's test it by just creating a half-meg file and using that as our
Xfilesystem.  First let's create the half-meg file:
X
Xdd if=/dev/full bs=....uh, what, you mean this is the filedisk
Xdistribution rather than the /dev/full driver distribution? ;-)
X
Xyes | dd conv=sync bs=65536 count=8 > bigfile
X
X(65536*8 is 512k; conv=sync makes dd pad each bufferful to the bs=
Xfigure.)  After a few seconds, dd will report 0+8 records in, 8+0
Xrecords out.  Then you will get a "Broken pipe" message, which you
Xshould ignore.  Now we connect this to unit 0:
X
X# fdconn 0 bigfile
X
XNow /dev/filedisk0 and /dev/rfiledisk0 are pseudo-filesystems
Xcontaining lots of junk.  Let's make a filesystem there:
X
X# /etc/mkfs /dev/rfiledisk0 1024
X....mkfs messages....
X
XNow sync the disk just to be safe.  It works just as well to run fsck
Xon it, I find; but if you do neither, I have had it crash mysteriously
Xsometimes (I suspect that some critical filesystem data, like
Xsuperblocks, is still waiting to be written to the disk, because the
Xmkfs used /dev/rfiledisk0 instead of /dev/filedisk0).
X
X# sync
X
XNow we can mount it somewhere:
X
X# /etc/mount /dev/filedisk0 /mnt
X
XAnd away we go!  Note that you pay two penalties for using this driver.
XOne is speed, of course; the other is storage space, since there is all
Xthe usual filesystem overhead.  Most of the uses for this driver are
Xsuch that these really don't matter.  For example, recently I wanted to
Xbuild a boot tape with a slightly non-standard mini-root filesystem on
Xit.  So I just used dd to copy the mini-root off the tape onto a disk
Xfile and then used this driver to mount the mini-root filesystem
Xsomewhere.  Then of course it was trivial to arrange things on the
Xmini-root as I wanted them.  Then just unmount and run fddisc, and use
Xdd to put it back on tape.
X
X					der Mouse
X
X				(mouse@mcgill-vision.uucp)
SHAR_EOF
if test 5589 -ne "`wc -c README`"
then
echo shar: error transmitting README \(should have been 5589 characters\)
fi
exit 0
# end of shell archive