Hi,
I just moved from pseudo distributed hadoop to a four machine full
distributed hadoop setup.

But, after I start the dfs, there is no live node showing up. If I make
master a slave too, then the datanode in master machine will show up.

I looked up all logs and found no errors. The only thing
looks suspicious  is the log in the datanode:
************************************
2010-03-17 02:39:04,003 INFO org.apache.hadoop.ipc.RPC: Server at
/xx.xx.xx.xx:9000 not available yet, Zzzzz...
2010-03-17 02:39:06,064 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 0 time(s).
2010-03-17 02:39:07,076 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 1 time(s).
2010-03-17 02:39:08,081 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 2 time(s).
2010-03-17 02:39:09,098 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx6:9000. Already tried 3 time(s).
2010-03-17 02:39:10,159 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 4 time(s).
2010-03-17 02:39:11,179 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 5 time(s).
2010-03-17 02:39:12,221 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 6 time(s).
2010-03-17 02:39:13,372 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 7 time(s).
2010-03-17 02:39:14,545 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 8 time(s).
2010-03-17 02:39:15,558 INFO org.apache.hadoop.ipc.Client: Retrying connect
to server: /xx.xx.xx.xx:9000. Already tried 9 time(s).
*************************************

Does anybody know what might cause this problem?

ssh among these machines are fine without password. The owner of hadoop
folder has been changed to the same hadoop user.

Thanks!
William