[oclug] *Why* aren't users generally able to umount?

[burns]

Michael Anderson wrote:
> 
> I've been configuring some Linux systems and mounting drives here,
> there, and everywhere.  I sometimes have the problem that I can not
> unmount something that I've mounted [.. the usual "blah-blah is not in
> fstab (and you are not root)" message].
> 
> My question is a general one: Is there some ominous security reason why
> an ordinary user should not be able to unmount something that s/he has
> successfully mounted?

Although maybe not the cause in this case, one usual cause of floppy
refusal is that you are trying to unmount something that you are
currently in: 

[michael /]$ cd auto/floppy
[michael floppy]$ umount /auto/floppy
umount: /mnt/floppy: device is busy
[michael floppy]$ ...nuts 

Not related to the above, it's also a good idea to do

sync
sync

before you umount. 

It flushes the buffers, ensuring that anything related to the floppy
(e.g.) is written to file before you unmount the drive.

-- 
burns