ubuntu安装hadoop注意（datenode连不上namenode）

datenode日志：

2013-10-30 10:40:00,753 INFO org.apache.hadoop.ipc.RPC: Server at prep-master/192.168.21.191:9000 not available yet, Zzzzz...

2013-10-30 10:40:02,754 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:03,755 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:04,756 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:05,757 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:06,758 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:07,758 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 5 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:08,759 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 6 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:09,760 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 7 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:10,761 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 8 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:11,762 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: prep-master/192.168.21.191:9000. Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)

2013-10-30 10:40:11,762 INFO org.apache.hadoop.ipc.RPC: Server at prep-master/192.168.21.191:9000 not available yet, Zzzzz...

解决方法：

修改namenode上hosts文件：

#127.0.1.1 prep-master---------一定要注释掉