I bought a Samsung ML-2510 laser printer the other day, and when installing using CUPS, I discovered that CUPS wasn't letting me add local printers of any kind. After a fashion I discovered that this is because the available printing backends in CUPS are determined by which files are present in /usr/lib/cups/backend. So one can add a missing backend by copying the missing backend from /usr/lib/cups/backend-available to /usr/lib/cups/backend.

In Debian, one can also fix this by running dpkg-reconfigure cups.

Update Nov 18, 2008 As ususal, I spoke too soon. The issue I was having is actually a CUPS permissions bug . I don't know why it worked for me Friday after fiddling with the above (and upgrading CUPS to Debian experimental), but today it was all broken again, so I had to fiddle some more.