To enable the finger print reader on a Dell XPS M1530 in Ubuntu 8.10 follow these steps:

After installing from the normal repositories coming with Ubuntu 8.10, you would have to press enter after sweeping finger. (This bug: https://bugs.launchpad.net/ubuntu/+source/thinkfinger/+bug/256429) Therefore Jon Oberheide made an update that can be found here: https://launchpad.net/~jon-oberheide/+archive

Add the PPA repositories to your source.list (/etc/apt/source.list):

deb http://ppa.launchpad.net/jon-oberheide/ubuntu intrepid main
deb-src http://ppa.launchpad.net/jon-oberheide/ubuntu intrepid main

Update installer:

$ sudo apt-get update

And install:

$ sudo apt-get install thinkfinger-tools

Now the driver is installed and should be working. You can try it with

tf-tool --acquire
tf-tool --verify

This will ask you to swipe your finger three times and save the fingerprint to ~/.thinkfinger.bir

Now we need to configure PAM to use finger print reader to authenticate.
Open /etc/pam.d/common-auth:

sudo /etc/pam.d/common-auth

On Ubuntu 8.10 - Intrepid Ibex you should just edit the section of the file that contains the pam_unix.so line so it looks like this:

....
# here are the per-package modules (the "Primary" block)
auth	sufficient	pam_thinkfinger.so
auth	[success=1 default=ignore]	pam_unix.so try_first_pass nullok_secure
# here's the fallback if no module succeeds
....

Save the file and reboot. You should now see the option to “Swipe your finger” at login and when issuing sudo commands.