Documentation for Hadoop configuration in PPA?

[Ｖ字龍(Vdragon)]

Hi,
I currently using your PPA for a school project and I wondered if there's any basic information like user/group/directory usage.
Ex.
* What actually does the package created hadoop group, mapred/hdfs user/group for
* How to properly use the package-created /var/lib/hadoop, /var/lib/hadoop/cache directory
Currently many tutorials on the web still using packages directly download from the official site for Hadoop deployment and don't include those info.
* $HADOOP_HOME/pids current points to an inexistent directory(/var/run/hadoop)
  *update* that link seems to be valid after installing hadoop-conf-pseudo
* Why does /etc/hadoop set to "not-writable" by users in hadoop group?

I'm working on a how-to using this PPA here:
https://docs.google.com/document/d/17DXgc1yOpIINrFWx5aFghhJAHwjemzx9VPnyb0gNHhY/edit#
(in Traditional Chinese)

Thanks a lot.