devfs and hot unplugging firewire device

[John-Mark Gurney]

M. L. Dodson wrote this message on Tue, Sep 19, 2006 at 11:25 -0500:
> On Tuesday 19 September 2006 11:04, John-Mark Gurney wrote:
> > M. L. Dodson wrote this message on Tue, Sep 19, 2006 at 10:05 -0500:
> > > When I finished a dump/restore, I just pulled the cable (the
> > > firewire disk partitions were not mounted).  When I plugged in the
> >
> > The problem is that the old devices still are open for writing.. If
> > you were to umount -f the old fs, most likely, the devices would
> > wither away, and things would be back to normal...
> 
> Hmmm... I just looked at the umount man page.  I guess the
> behaviour you describe can be implied by it, but it is certainly
> not obvious (at least to me).  So, if I understand you, if instead
> of "umount /mnt", I do "umount -f /mnt", the behaviour will be as
> I expected: the device will be completely unmounted and the device
> will disappear when I pull the cable?

The -f is only necessary if you've already removed the drive... You
should be able to do a normal umount /mnt before you pull the drive
and then everything will just work...

> > I hope you were fsync'ing the files before you unmounted the disk
> > to ensure that the file was completely written to disk, otherwise
> > you could end up w/ the an incomplete file...
> 
> Actually, my sequence was: fsck the /dev/da0s1* (excluding b and
> c), and that was where I noticed the problem (on the second
> firewire disk in the sequence of 7 disks dumped), then dump the g
> partition to a file on the server's main disk.  Then I did a
> restore -if <dumped to file> in the directory I wanted the stuff
> to go into.  I did it this way so I could exclude some unimportant
> stuff that was in the /home directory on the firewire disk
> (corresponding to /dev/da0s1g).  The only time I mounted the disk
> was to rsync between the firewire /home (/dev/da0s1g) and the
> restored data directory to check for errors.  (This data cost
> weeks of computation for many of the files, so better to take a
> little time to wear belt AND suspenders).  The firewire disk was
> only ever read from, not written to except for the fsck.  Your
> answer implies to me that if I had never mounted the device it
> would have gone away when I pulled the cable.  Right?

Correct...

> > > My question: Should I be doing something to signal devfs I'm going
> > > to unplug a device so it won't get confused when I plug in another
> > > similar, but not the same, device?  camcontrol commands like
> > > "camcontrol eject <options>" and "camcontrol rescan all" seemed to
> > > not have the results I expected.  What's going on here?
> >
> > umount the file system...  I unplug firewire drives that don't have
> > mounted filesystems, and haven't had an issue with it...
> 
> OK, that is certainly what I get from your first couple of
> paragraphs.  Thanks for the explanation!

np...

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."