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Using Gnome-Volume-Manager
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The gnome-volume-manager will automatically mount
removable devices as they are connected. It is run as part of the
default Debian session, but will also be started, if needed, if you
enter the Removable Drives and Media application under Desktop,
Preferences menu. Otherwise it will need to be run in your session
(add gnome-volume-manager to
Desktop PreferencesSessions). The users need
to be in group plugdev.
Note that this works best when you run a single X-session at a time
(which is the common scenario). If you have two or more users with
concurrent X-sessions on different tty's the permissions become an
issue. In this situation it is perhaps best to use the Disk Mounter
applets to do the mounting.
If you prefer to give gnome-volume-manager a try in the
situation with concurrent users with different X sessions on the one
console, and for trusted users (those in plugdev), you could
use the following /etc/fstab entry:
/dev/usbkey /media/usbkey auto users,gid=plugdev,umask=0002,defaults
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The main points here are the use of users to allow any user
to unmount the device, and when mounting the device the gid
(group ID) is set to plugdev. The umask then allows
group access but not others.
The pmount command is the basis of
gnome-volume-manager and is hard coded in the
gnome-volume-manager:
$ strings /usr/bin/gnome-volume-manager | grep pmount
/usr/bin/pmount-hal %h
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Also pmount's policy is hard-coded and so also
has limited configurability. Part of pmount's policy is that you need
to be able to run pmount in order to mount a device, and so you need
to be in the plugdev group to mount a device. An entry in
/etc/fstab overrides pmount's policy.
In order to be able to umount a device, the device needs to have been
mounted by the user. This is enforced by checking /etc/mtab
and parsing the mount options looking for  .  needs to be
the uid of the user trying to unmount the device. The policy is that
if you can run pmount and fulfill certain criteria, you can mount a
device. And pumount's policy is that if you are the user who mounted
the device and fulfill certain criteria, you can unmount the device.
But if you have two gnome-volume-manager's running, both
will get messages from HAL which means that they will race for
mounting the device. Ideally one of them should go to sleep!
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