Re: unique identifiers for cdrom drives
On 20110516_120833, Camaleón wrote:
> On Sun, 15 May 2011 13:39:20 -0600, Paul E Condon wrote:
>
> > On 20110514_160848, Camaleón wrote:
>
> (...)
>
> >> > I've googled and see reference to vol_id, but I don't have vol_id,
> >> > and can't find it, or even a man page.
> >>
> >> There is a file located at "/etc/udev/rules.d/70-persistent-cd.rules"
> >> that can be manually edited to make static names for the optical
> >> devices (or so it seems), maybe you can do something there.
> >
> > Thanks.
> > I'm reading
> >
> > http://www.debian.org/doc/manuals/debian-reference/ch01.en.html#_device_files
> > and
> > http://www.reactivated.net/writing_udev_rules.html#about
> >
> > looking for how to write a rule that meets my needs. But I have a
> > problem understanding. I don't see anything in udev rules that allows me
> > to control the mount point of a device, i.e. what connects the symlink
> > /dev/cdrom, with the mountpoint /media/cdromX ? Udev rules seem to be
> > concerned only with what appears in /dev/ .
> >
> > What am I missing? Is there a fixed, invariant mapping that just always
> > happens?
>
> How does your "/etc/udev/rules.d/70-persistent-cd.rules" look like?
There are too many entries in it. More entries than I have ever had distinct
cdrom drives installed. I think these spurious entries maybe part of the
problem. OTOH, the initial problem of the two drives swapping identities
has gone away without my having done anything, at least nothing intentional.
I had always been using what happens to cdrom trays when I issue eject
commands with various device and/or mount-point strings. Now the result is
consistent. I am waiting to see if the problem returns. As it is, there is
nothing to fix. I'm not inclined to attempt to break it so that I can
continue trying to fix it. I don't see why any of the few updates that have
happened would have fixed this.
I have learned a lot, so my efforts, and yours, have not been entirely
wasted. Thanks. And we shall see, some day.
>
> I thought udev should manage this automatically without needing to make
> static mount points in "/etc/fstab" in the same way it does when you
> insert an USB flash drive and it gets mounted under "/media/MYUSB_TAG"
> unless you tell otherwise :-?
I distinctly remember that some time in the past, the static mount
point definitions for cdroms disappeared from /etc/fstab. It was about
the time that Squeeze/testing started using sdxn rather than hdxn block
device names. But now when I looked again, the cdroms are mentioned in
/etc/fstab just as Andrei said they should be. You might think that their
being there is good, but a further check of system backups shows no
indication that they were once missing. I could have failed to do any
backups during that time, but I just don't know.
USB hard disks that are formatted with ext2/3/4 and have partition labels
get mounted automatically in /media with that partition labels used as
mount points. The mount points are created as needed, and deleted when
the 'safe demount' icon is clicked. Some of my USB hard disks are
Western Digital models that have 'Virtual CDroms' installed on the disk.
I think these may be a source of clutter in 70-persistent-cd.rules.
I need a rest from thinking about this. The lack of a demonstrable problem
now is forcing be to take one.
--
Paul E Condon
pecondon@mesanetworks.net
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