1.修改机器/etc/hostname分别为
master
slave1
slave2
重启
2.修改/etc/hosts，删除多余项
192.168.2.223 master
192.168.2.222 slave2
192.168.2.224 slave1
注释掉127.0.0.1 localhost回环地址，及其它127.0.0.1地址和包含[master|slave1|slave2]的项
3.添加hadoop：hadoop用户名和组
4.安装免登陆SSH
5.安装JDK
6.安装hadoop
7.注意删除hadoop目录下dfs/data、tmp目录的所有文件
出错：
2015-11-11 01:26:28,191 FATAL org.apache.hadoop.hdfs.server.datanode.DataNode: Initialization failed for Block pool <registering> (Datanode Uuid unassigned) service to master/172.17.0.27:9000.
Exiting.
java.io.IOException: Incompatible clusterIDs in /usr/local/hadoop-2.6.0/dfs/data: namenode clusterID = CID-8a0b27a3-b53c-4e97-81e4-6937db707fc9; datanode clusterID = CID-b948da8a-e05a-4c45-97ff-7c2446000fb0
解决：查看dfs/name/current/VERSION中的clusterID ，将其余节点都改为这个值。
2015-11-11 02:36:18,651 FATAL org.apache.hadoop.hdfs.StateChange: BLOCK* NameSystem.getDatanode: Data node DatanodeRegistration(172.17.0.24, datanodeUuid=6892adc4-0d44-4124-ba2a-927eee507954, infoPort=50075, ipcPort=50020, storageInfo=lv=-56;cid=CID-9cb6ddf6-1e61-4b34-906b-690ede335e8e;nsid=1714433657;c=0)
is attempting to report storage ID 6892adc4-0d44-4124-ba2a-927eee507954. Node 172.17.0.28:50010 is expected to serve this storage.
解决：
删除tmp文件夹里文件
删除dfs/data
bin/hadoop datanode -format
2015/11/11 03:26:03 INFO mapreduce.JobSubmitter: Cleaning up the staging area /tmp/hadoop-yarn/staging/root/.staging/job_1447211927171_0001
org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.server.namenode.SafeModeException): Cannot delete /user/root/grep-temp-909165866. Name node is in safe mode.
The reported blocks 27 needs additional 8 blocks to reach the threshold 0.9990 of total blocks 35.
The number of live datanodes 3 has reached the minimum number 0. Safe mode will be turned off automatically once the thresholds have been reached.
解决：
yarn-site.xml添加：
<property>
<name>yarn.resourcemanager.hostname</name>
<value>master</value>
</property>
<name>yarn.resourcemanager.hostname</name>
<value>master</value>
</property>
强制关闭
bin/hadoop dfsadmin -safemode leave
用户可以通过dfsadmin -safemode value 来操作安全模式，参数value的说明如下：
enter - 进入安全模式
leave - 强制NameNode离开安全模式
get - 返回安全模式是否开启的信息
wait - 等待，一直到安全模式结束。
2015-11-11 01:56:55,795 WARN org.apache.hadoop.hdfs.server.datanode.DataNode: IOException in offerService
java.io.EOFException: End of File Exception between local host is: "slave2/172.17.0.25"; destination host is: "master":9000; : java.io.EOFException; For more details see: http://wiki.apache.org/hadoop/EOFException
解决：重新格式化NameNode
MapReduce卡住：
解决方法：
删除/etc/hosts中多余的项，比如：
127.0.0.1 localhost
127.0.0.1 slave1
不能用127.0.0.1代替本机地址，对应的错误：
2013-10-15 09:52:31,351 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: sunliang/192.168.1.232:9000. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)
2013-10-15 09:52:32,352 INFO org.apache.hadoop.ipc.Client: Retrying connect to server: sunliang/192.168.1.232:9000. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1 SECONDS)
解决：
删除/etc/hosts中多余的项
删除所用的tmp文件夹，然后执行hadoop namenode -format 进行格式化，在重新启动start-all.sh
还有个问题就是有防火墙，关闭防火墙
