大讲台谈搭建Hadoop环境常见的问题及解决方案(二)

本文中所涉及到的问题均来自大讲台Hadoop学员的提问，下面是具体问题描述及解决方案，希望对正在学hadoop的学子有所帮助。

问题1：hadoop启动？

问题描述：前序步奏已经完成，然后使用命令 start-all.sh 启动 hadoop 的时候出现这个问题，请问怎么解决？

解决方案：ssh 没有配置成功。按照环境安装课件中的ssh配置步骤，再完整操作一次就可以了。

问题2：搭建eclipse开发环境中，有一步时设置本地Hadoop安装运行目录

问题描述：请问下，设置本地Hadoop安装运行目录有什么用处？程序不都是连接到远程机器上运行么？

解决方案：设置本地 hadoop安装目录，目的是方便本地 MapReduce 项目的创建和程序的开发，创建 Map/Reduce 项目的时候自动会引进 hadoop 所需要的jar包，不需要额外的添加。MapReduce程序可以在本地测试运行也可以连接到 Hadoop 集群上面执行。

问题3：hadoop 启动报错了，不知道为什么？

问题描述：

chaiying0@ubuntu:~$ /home/hadoop/hadoop-0.20.2/bin/start-all.sh

starting namenode, logging to /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-namenode-ubuntu.out

/home/hadoop/hadoop-0.20.2/bin/hadoop-daemon.sh: line 117: /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-namenode-ubuntu.out: Permission denied

head: cannot open `/home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-namenode-ubuntu.out' for reading: No such file or directory

localhost: starting datanode, logging to /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-datanode-ubuntu.out

localhost: /home/hadoop/hadoop-0.20.2/bin/hadoop-daemon.sh: line 117: /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-datanode-ubuntu.out: Permission denied

localhost: head: cannot open `/home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-datanode-ubuntu.out' for reading: No such file or directory

localhost: starting secondarynamenode, logging to /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-secondarynamenode-ubuntu.out

localhost: /home/hadoop/hadoop-0.20.2/bin/hadoop-daemon.sh: line 117: /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-secondarynamenode-ubuntu.out: Permission denied

localhost: head: cannot open `/home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-secondarynamenode-ubuntu.out' for reading: No such file or directory

starting jobtracker, logging to /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-jobtracker-ubuntu.out

/home/hadoop/hadoop-0.20.2/bin/hadoop-daemon.sh: line 117: /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-jobtracker-ubuntu.out: Permission denied

head: cannot open `/home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-jobtracker-ubuntu.out' for reading: No such file or directory

localhost: starting tasktracker, logging to /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-tasktracker-ubuntu.out

localhost: /home/hadoop/hadoop-0.20.2/bin/hadoop-daemon.sh: line 117: /home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-tasktracker-ubuntu.out: Permission denied

localhost: head: cannot open `/home/hadoop/hadoop-0.20.2/bin/../logs/hadoop-chaiying0-tasktracker-ubuntu.out' for reading: No such file or directory.

感觉里面有两个错误，一个是permission denied，另一个是no such file or directory。请问怎么解决啊.

解决方案：你当前用户没有权限打开 hadoop下的logs 文件。你可以使用 ls -al 查看一下，logs文件的权限是否属于当前用户。

你需要使用 sudo chownchaiying0:chaiying0 logs 命令 来赋予当前用户 chaiying0权限。