[Techtalk] Can't umount floppy

Conor Daly conor.daly at oceanfree.net
Wed Apr 16 00:04:28 EST 2003

On Tue, Apr 15, 2003 at 05:49:32AM -0700 or so it is rumoured hereabouts, 
Berenice thought:
> I sometimes get the "can't unmount - device is busy" message when I
> try to umount my floppy. I didn't know what to do when this happened
> the other day, so I ejected the disk and discovered today I'd lost
> everything on it.  Luckily I have a copy of the files on the hard
> drive. 

Typically, disk writes are buffered and only written to disk from time to
time.  When you umount a disk, any outstanding buffers are flushed to disk
before the disk is unmounted.  You'll see this with floppies if you mount,
cp to floppy, umount.  It will take some time (the floppy busily clunks
away) for the prompt to return after the umount because it's fushing the
buffer to disk.  When you ejected the floppy without umounting first, the
data hadn't been physically written to the disk.

Conor Daly <conor.daly at oceanfree.net>

Domestic Sysadmin :-)
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