How to enable integrated fingerprint reader with fprint
Ubuntu 11.04
The UPEK integrated fingerprint reader on the ThinkPad X220 is supported in Ubuntu 11.04 (natty).
Install the necessary packages if they aren't already present.
aptitude install libpam-fprintd
Observe that the needed lines in common-auth are already present.
$ grep fprint /etc/pam.d/common-auth auth [success=2 default=ignore] pam_fprintd.so
Log in to the desktop. Open a terminal. In the terminal run fprintd-enroll and swipe your right index finger five times. Now you should be able to authenticate by swiping your right index finger.
If you have an encrypted home directory then logging in from GDM by fingerprint is broken: the home directory cannot be decrypted. The solution is to log in with a password.
Problem is that GDM follows the default authentication procedure which starts with an attempt to read a fingerprint. Only once this fails or times out is a password requested. That is not convenient. To eliminate fingerprint authentication from GDM login, edit /etc/pam.d/gdm so that it includes /etc/pam.d/common-auth-nofinger rather than /etc/pam.d/common-auth; copy /etc/pam.d/common-auth to /etc/pam.d/common-auth-nofinger and remove the line auth [success=3 default=ignore] pam_fprintd.so from the latter.