hadoop格式化报错："May not run daemons as root. Please specify HADOOP_NAMENODE_USER"的解决办法

Problem:

刚在我机子上运行hadoop，结果碰上下面这问题：

[root@myServer hadoop-0.20.2-cdh3u4]# hadoop namenode -format
May not run daemons as root. Please specify HADOOP_NAMENODE_USER
解决这问题的思路就是：让你家linux生宝宝（新增个用户进去）。

打开这个文件：/opt/hadoop/hadoop-0.20.2-cdh3u4/conf/hadoop-env.sh 嗯，对了，你的路径可能不是这儿，随机应变吧~
在打开的文件结尾处，把下面这段儿给整上去。         ps:记得把<username>改成宝宝的名字(linux 用户名)，造吗？

export HADOOP_NAMENODE_USER="<username>"
export HADOOP_SECONDARYNAMENODE_USER="<username>"
export HADOOP_JOBTRACKER_USER="<username>"
export HADOOP_DATANODE_USER="<username>"
export HADOOP_TASKTRACKER_USER="<username>"
把你的命令再运行一遍，完事你就知道结果了。（要想知道正确姿势，请咨询 CSDN:薛沛雷哥哥    嘿嘿）

14/11/01 18:25:34 INFO namenode.NameNode: STARTUP_MSG:
/************************************************************
STARTUP_MSG: Starting NameNode
STARTUP_MSG: host = myServer/145.32.4.5
STARTUP_MSG: args = [-format]
STARTUP_MSG: version = 0.20.2-cdh3u4
STARTUP_MSG: build = git://ubuntu-slave01/var/lib/jenkins/workspace/CDH3u4-Full-RC/build/cdh3/hadoop20/0.20.2-cdh3u4/source -r 214dd731e3bdb687cb55988d3f47dd9e248c5690; compiled by 'jenkins' on Mon May 7 13:01:39 PDT 2012
************************************************************/
14/11/01 18:25:34 INFO util.GSet: VM type = 64-bit
14/11/01 18:25:34 INFO util.GSet: 2% max memory = 17.78 MB
14/11/01 18:25:34 INFO util.GSet: capacity = 2^21 = 2097152 entries
14/11/01 18:25:34 INFO util.GSet: recommended=2097152, actual=2097152
14/11/01 18:25:34 INFO namenode.FSNamesystem: fsOwner=unisys (auth:SIMPLE)
14/11/01 18:25:34 INFO namenode.FSNamesystem: supergroup=supergroup
14/11/01 18:25:34 INFO namenode.FSNamesystem: isPermissionEnabled=true
14/11/01 18:25:34 INFO namenode.FSNamesystem: dfs.block.invalidate.limit=1000
14/11/01 18:25:34 INFO namenode.FSNamesystem: isAccessTokenEnabled=false accessKeyUpdateInterval=0 min(s), accessTokenLifetime=0 min(s)
14/11/01 18:25:35 INFO common.Storage: Image file of size 112 saved in 0 seconds.
14/11/01 18:25:35 INFO common.Storage: Storage directory /tmp/dfs/name has been successfully formatted.
14/11/01 18:25:35 INFO namenode.NameNode: SHUTDOWN_MSG:
/************************************************************
SHUTDOWN_MSG: Shutting down NameNode at myServer/145.32.4.5
************************************************************/

对了，你可能会转角遇到爱，看见log4j errors这个宝贝玩意儿，别害怕，切换到新用户(su username)，再试试。

翻译自：http://www.myonestopforum.com/viewtopic.php?f=21&t=4173#.Vq8WSuIZ7J_