Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP 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 Lines: 174 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