cloudera 0.18 -> 0.20

 * hadoop install 
{{{
$ apt-get install hadoop-0.18 hadoop-0.18-namenode hadoop-0.18-datanode hadoop-0.18-jobtracker hadoop-0.18-tasktracker hadoop-conf-pseudo
}}}

 * hadoop namenode format
{{{
$ sudo su -s /bin/bash - hadoop -c 'hadoop namenode -format'
}}}