couldnot start all process in hadoop

[Mahender]

Hi,

I have followed all steps mentioned in http://chennaihug.org/knowledgebase/ regarding psuedo distribution mode installation, but i am observing that datanode and Name node are not starting when i give start-dfs.sh, some times only name node starts and datanode doesnot start,

i mean i never saw in my jps console that all nodes started, do i need to delete tmp files every time i start, and also do i need to format name node every time i start-dfs.sh.
also do i need to switch on the machine all time so that the nodes will be in started mode.


thanks
Mahender