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问题描述
我在伪分布式模式下使用Hadoop 1.0.3。我的conf / core-site.xml设置如下：
< configuration>
<属性>
<名称> fs.default.name< /名称>
< value> hdfs：// localhost：9000< / value>
< / property>
<属性>
<名称> mapred.child.tmp< / name>
<值> / home / administrator / hadoop / temp< /值>
< / property>
< / configuration>
所以我相信我的默认文件系统被设置为HDFS。
然而，当我运行下面的代码：
Configuration conf = new Configuration（）;
FileSystem fs = FileSystem.get（conf）;
我以为fs应该是 DistributedFileSystem 实例。然而，事实证明是 LocalFileSystem 实例。
但是，如果我运行以下代码：
Configuration conf = new Configuration（）;
conf.set（fs.default.name，hdfs：// localhost：9000）;
FileSystem fs = FileSystem.get（conf）;
然后我可以得到 DistributedFileSystem fs。
不是我的默认FileSystem在core-site.xml中设置为HDFS吗？如果没有的话，我应该怎么设置呢？
解决方案 Eclipse环境不知道在Hadoop安装目录下的conf目录下找到conf目录core-default.xml和core-site.xml，除非将这些文件添加到Eclipse类路径中以便首先加载。由于这些不会在eclipse classpath中添加，所以默认的core-site.xml将从jar文件中加载hadoop - * - core.jar（例如： hadoop-0.20.2-core.jar for version 0.20），它具有本地系统作为默认文件系统，因此您看到 LocalFileSystem 对象而不是因此，将< HADOOP_INSTALL> / conf 目录添加到分发文件系统。
eclipse项目类路径，转到项目属性（项目 - >属性） - > Java构建路径 - >库选项卡 - >添加外部类文件夹 - >从
< HADOOP_INSTALL> $ b
上面的代码应该把你的`/core-site.xml'添加到你的eclipse类路径中，并且所有的设置都应该覆盖默认的。
I am using Hadoop 1.0.3 in a Pseudo-Distributed mode. And my conf/core-site.xml is set as follows:
<configuration>
<property>
<name>fs.default.name</name>
<value>hdfs://localhost:9000</value>
</property>
<property>
<name>mapred.child.tmp</name>
<value>/home/administrator/hadoop/temp</value>
</property>
</configuration>
So I believed that my default filesystem is set to HDFS.However, when I run the following code:
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
I thought that fs should be a DistributedFileSystem instance. However, it turns out to be LocalFileSystem instance.
But, if I run the following code:
Configuration conf = new Configuration();
conf.set("fs.default.name", "hdfs://localhost:9000");
FileSystem fs = FileSystem.get(conf);
Then I can get a DistributedFileSystem fs.
Isn't my default FileSystem set to HDFS in core-site.xml? If not, how should I set that?
解决方案
Eclipse environment doesn't know where the conf directory under Hadoop install directory to find the core-default.xml and core-site.xml unless these files are added to the Eclipse classpath to load first.
Since these are not added in the eclipse classpath, the default core-site.xml will be loaded from the jar file hadoop-*-core.jar (For eg: hadoop-0.20.2-core.jar for version 0.20) which has the local system as default file system and hence you are seeing LocalFileSystem object instead of DistributedFileSystem.
So, to add the <HADOOP_INSTALL>/conf directory to eclipse project classpath, goto the project properties(project -> properties) -> Java build path -> Libraries tab -> Add external class folder -> Select the conf directory from <HADOOP_INSTALL>
The above should add your `/core-site.xml' to your eclipse classpath and all your settings should override the default ones.
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