Now For The Tech
First off, the setup. This particular system is a Lenovo Desktop, running a generic build of Ubuntu 9.04 Jaunty Jackalope, the 2.6.28-11 Linux Kernel, and as for the scanner, it is whatever fingerprint scanner is built into Lenovo keyboard model KUF0452. My Google-ing immediately returned the Think Finger driver and in particular this wiki entry for enabling the fingerprint reader.
I followed the instructions for Jaunty specifically, starting with enabling the proper GPG signing key, continued with adding the repos and finally downloading the packages appropriately. The tf-tool program was installed correctly and I could correctly acquire and verify fingerprints assigned to different users. I also followed the instructions for linking the authentication to the Pluggable Authentication Module (PAM) daemon which included running this simple command on Jaunty:
$ sudo /usr/lib/pam-thinkfinger/pam-thinkfinger-enable
This command goes and automatically edits your
/etc/pam.d/common-auth file to have the appropriate entries for the think finger module. With this done, I rebooted (unnecessary, but a habit). Upon reboot, I typed my username, and subsequently the system asked me for, “Password or swipe finger.” Success! I thought. But alas, it was not meant to be. Upon swiping my finger, it would register the read but then reject with the error that, “The username of password was not correct. Trying checking the case of the letters,” or something to that effect.