If you do not have build-essentials and kernel header installed the DKMS build steps will fail during the install of
ubuntu-zfs. Were any error messages written to the console?
I ran into a similar problem. I attempted to install
ubuntu-zfs BEFORE installing
build-essentials and the kernel headers. That left a bit of a mess. Removing
ubuntu-zfs does not remove all of it's dependencies. I had to:
dpkg --list | grep zfs
dpkg --list | grep spl
and track down the packages that were not removed by apt-get purge ubuntu-zfs.
After cleaning things up and installing the correct pre-requisites the install worked but still failed to correctly configure the modules to load.