I am using ubuntu 12.02 32bit and have installed hadoop2.2.0 and pig 0.12 successfully. Hadoop runs properly on my system.
However,
Apache Pig 0.12.0 expects an older version of Hadoop by default. You must recompile Pig for Hadoop 2.2.0 and replace two jars with new pig-0.12.1-SNAPSHOT.jar and pig-0.12.1-SNAPSHOT-withouthadoop.jar.
For recompilation unpack the pig archive, go to the directory "pig-0.12.0" and just run:
ant clean jar-all -Dhadoopversion=23