There are apparently two ways to activate the Fingerprint Reader with 1) ThinkFinger (https://wiki.ubuntu.com/ThinkFinger from Synaptic) and 2) Fprint from here https://launchpad.net/~fingerprint/+archive/fprint (fprint is also in Synaptic but something is missing). Long story short (kinda): Quick installation guide
1. You should be running Ubuntu 10.04, 11.04, 11.04, or any derivative thereof. Packages for Ubuntu 9.10 are also available, but you won't be able to avoid one minor annoyance (see known issue 2 below).
2. You need to have a supported fingerprint reader. See the list at http://reactivated.net/fprint/wiki/Supported_devices. You may ignore columns Vendor and Product, only look at USB Vendor ID and USB Product ID. You can find out your reader's IDs with the lsusb command, the sixth column of which has the form of xxxx:yyyy, where xxxx is the Vendor ID and yyyy the Product ID. Another supported device, not listed at the above website, is 147e:1000.
3. Add this PPA to your sources:
sudo add-apt-repository ppa:fingerprint/fprint
sudo apt-get update
sudo apt-get upgrade
3. Install fprint-demo (the version from standard Ubuntu archive is obsolete).
sudo apt-get install libfprint0 fprint-demo
4. Go to Applications > Accessories > fprint project demo and check that you can enroll and verify your fingerprints and that your reader is indeed supported.
5. Install libpam-fprintd (not to be confused with libpam-fprint, the final “d” is crucial).
sudo apt-get install libpam-fprintd
Note: If you have experimented with fingerprint authentication before and have changed your /etc/pam.d/common-auth, you may be presented with a screen asking whether you want to override those changes. Select Yes. Under very special circumstances, you may get an error saying
pam-auth-update: Local modifications to /etc/pam.d/common-*, not updating.
pam-auth-update: Run pam-auth-update –force to override.
In this case, run “sudo pam-auth-update –force”, exactly as suggested, and enable the fprintd profile manually. Leave the standard system profiles (Unix, Keyring and ConsoleKit) enabled as well.
6. Go to System > Preferences > About Me and in the top-right corner set up your fingerprint authentication. Alternatively, you can use command fprintd-enroll if you prefer CLI.
7. If you are running Lucid or newer, install gksu-polkit.
sudo apt-get install gksu-polkit (my note - I didn’t need to install this)
8. Test it: Lock and unlock screen, log out and back in, try sudo in terminal. Don't try to launch Synaptic (or a similar graphical application requiring unrestricted root privileges) yet, see issue 2 below first.