How to enable integrated fingerprint reader with fprint
Ubuntu 11.04
The integrated fingerprint reader on the ThinkPad X220 (at least) is supported in Template:Ubuntu 11.04 (natty).
Install the necessary packages if they aren't already present.
aptitude install libpam-fprintd
Confirm 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 or a password-protected default keyring then logging in from GDM by fingerprint is broken: the home directory cannot be decrypted. To deal with this, 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.