hadoop常见问题解决：
-----------------------------------------------------------
WARN mapred.LocalJobRunner: job_local910166057_0001
org.apache.hadoop.security.AccessControlException: org.apache.hadoop.security.AccessControlException: Permission denied: user=***, access=WRITE, inode="wordcount":root:supergroup:rwxr-xr-x
sulution：added this entry to conf/hdfs-site.xml
<property>
<name>dfs.permissions</name>
<value>false</value>
</property>
--------------------------------------------------------------
ERROR org.apache.hadoop.hdfs.server.namenode.SafeModeException:
Cannot create /mapreduce/wordcount/output/1. Name node is in
safe mode.
代码中添加
conf.set("dfs.permissions","false");
-------------------------------------------------------------
ERROR security.UserGroupInformation: PriviledgedActionException as:bc_qi cause:org.apache.hadoop.mapred.FileAlreadyExistsException: Output directory /mapreduce/wordcount/output/1 already exists
执行
hadoop fs -rmr /mapreduce/wordcount/output
-------------------------------------------------------------
提示连不上 50010 端口；
查看是不是防火墙的原因。
照样子添加 /etc/sysconfig/iptables 端口过滤
------------------------------------------------------------
