Which ones are recommended introductions to Hadoop 2.0 (YARN)? Pointers to webpages are good.
Those are good ones that I find:
The SoCC13 paper "Apache Hadoop YARN: Yet Another Resource Negotiator" by Vinod Kumar Vavilapalli et al.: http://www.socc2013.org/home/program/a5-vavilapalli.pdf
The introduction from Hortonworks by Arun Murthy:http://hortonworks.com/blog/apache-hadoop-yarn-concepts-and-applications/
The "Official" one from Apache Hadoop website (very brief):https://hadoop.apache.org/docs/r2.2.0/hadoop-yarn/hadoop-yarn-site/YARN.html