Install the thinkfinger-tools (for acquiring/verifying) and libpam-thinkfinger (for PAM integration):

sudo aptitude install thinkfinger-tools libpam-thinkfinger

Then you can test acquisition/verification. As a user, issue the commands:

tf-tool --acquire
# swipe 3 times your finger
tf-tool --verify
# swipe your finger, then another finger...

Note: tf-tools should work without being root if the user belongs to the plugdev group.

Then plug the reader to PAM as explained in /usr/share/doc/libpam-thinkfinger/README.Debian:

sudo /usr/lib/pam-thinkfinger/pam-thinkfinger-enable

Now restart your system and try swiping your finger in place of typing the password. A “Password or swipe finger:” prompt displays to authenticate you at GDM login and when you type “sudo”.

Notes:

• Test several programs in the Administration menu. “swipe finger” is not always showed but should work though.
• To my knowing, it doesn’t work when locking screen (gnome-screensaver).

References :

• http://www.thinkwiki.org/wiki/How_to_enable_the_fingerprint_reader_with_ThinkFinger
• http://thinkfinger.sourceforge.net/
• http://doc.ubuntu-fr.org/thinkfinger
• https://wiki.ubuntu.com/ThinkFinger