Mira este enlace:.
http://timocharis.com/help/udev.html
udev, Persistent Storage & Multi-card Readers
For anyone who joined the game late, there is a unique problem
regarding multicard readers and udev: they don't generate an OS event
when you plug in a card. From the computer's point of view, nothing
happened. Therefore, without polling the reader's slots to see if
there's a card present, udev has no way to know if there's a need for
a new device file in /dev. This was previously handled by
hald-addon-storage which would start a daemon to poll each device (a
separate daemon for each slot of a multicard reader, for example). If
it spotted something, it would signal udev to create the appropriate
device.