UNIX filesystems on Sun SPARCstation floppy disks

[Peter Lamb]

peter at ficc.ferranti.com (Peter da Silva) writes:

>In article <1991Apr18.174329 at quercus.gsfc.nasa.gov> karl at quercus.gsfc.nasa.gov (Karl Anderson) writes:
>> I know this has been discussed, but I missed it.  What I want to know
>> is, can 3-1/2" floppy disks with UNIX filesystems on them be mounted,

Yes indeed. I have even been able to mount floppies made on a Sony NeWS
on my SS1+ (the U*nix file systems are generally not designed for
portability across architectures; you shouldn't expect this to always
work, but sometimes it does).

>I'd like to know this, too. Information on how to format and mkfs them
>would be nice as well...

<barossa> fdformat -l
Press return to start formatting floppy.
................................................................................
<barossa> /etc/newfs /dev/rfd0c
/dev/rfd0c:     1440 sectors in 80 cylinders of 2 tracks, 9 sectors
        0.7MB in 5 cyl groups (16 c/g, 0.15MB/g, 64 i/g)
super-block backups (for fsck -b #) at:
 32, 336, 608, 912, 1184,
<barossa> su
Password:
barossa[prl]# mount /dev/fd0c /mnt
barossa[prl]# ls -la /mnt
total 10
drwxr-xr-x  3 root          512 Apr 24 08:55 ./
drwxr-sr-x 11 root          512 Apr 24 08:34 ../
drwxr-xr-x  2 root         8192 Apr 24 08:55 lost+found/
barossa[prl]# umount /mnt
barossa[prl]# <barossa>

This is for a so-called 1MB floppy (720k after formatting) or DSDD.
For a `2MB' floppy (1440k after formatting) or DSHD, omit the -l option.

This leaves you with:
<barossa> df /dev/rfd0c
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/rfd0c               583       9     515     2%

Since space is a premium on a floppy, you may want to add some mkfs options
to the newfs:

/etc/newfs -o space -m 0 /dev/rfd0c	# optimise disk layout for space, allow
					# use of whole disk
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/rfd0c               583       9     574     2%

If you can live with a bot more of a performance drop, add

-t 10		(lie about the head arrangement; this makes the disk a
		 single cylinder group, and reduces overhead. For a DSHD
		 disk, use -t 20)

Filesystem            kbytes    used   avail capacity  Mounted on
/dev/rfd0c               647       9     638     1%

I normally use floppies for saving software source in compressed tar
files. This means that there aren't many files, and so I don't need
many inodes, so add:

-i 8192		(tell newfs you have a larger-than-average file size)

Filesystem            kbytes    used   avail capacity  Mounted on
/dev/rfd0c               671       9     662     1%


So, now you have 662 of the 720k available for use (with default parameters
515k).



The security of permitting random users to mount filesystems that they
can tweak themselves is not addressed here ;-)


--
Peter Lamb
uucp:  uunet!mcsun!ethz!prl	eunet: prl at iis.ethz.ch	Tel:   +411 256 5241
Integrated Systems Laboratory
ETH-Zentrum, 8092 Zurich