After Oracle 11g very good experience with installing on Ubuntu I had high hopes for 12C also. They crumbled down quite fast. This is the summary of almost 2 days lost trying to install oracle on Ubuntu with the ups and downs.
First the conclusion: my personal conclusion is that oracle 12c does not work, with an acceptable amount of effort, on Ubuntu 14.04. It should be possible to install it following a guide but it’s by no means comparable to an 11g install. Most of the errors are in the linking phase where you have to manually edit the makefiles to add various missing (not found in current config) libraries. Finally I managed to install oracle 12C using a docker container using this guide but this is also not without problems.