blocks|key|245713|text|您可以使用GenericOptionsParser将Hadoop的设置加载到配置类型的对象并迭代其属性。以下是通过一个实用程序类(已配置)演示此方法的示例。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|245714|public+class+ConfigPrinter+extends+Configured+implements+Tool+{
++++static+{
++++++++//+by+default+core-site.xml+is+already+added
++++++++//+loading+"hdfs-site.xml"+from+classpath
++++++++Configuration.addDefaultResource("hdfs-site.xml");
++++++++Configuration.addDefaultResource("mapred-site.xml");
++++}

++++@Override
++++public+int+run(String[]+strings)+throws+Exception+{
++++++++Configuration+config+=++this.getConf();
++++++++for+(Map.Entry<String,+String>+entry+:+config)+{
++++++++++++System.out.println(entry.getKey()+%2B+"+=+"+%2B+entry.getValue());
++++++++}
++++++++return+0;
++++}

++++public+static+void+main(String[]+args)+throws+Exception+{
++++++++ToolRunner.run(new+ConfigPrinter(),+args);
++++}
}|code-block|syntax|javascript|245715|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can use GenericOptionsParser to load Hadoop's setting to Configuration-typed object and iterate its properties. Here is an example demonstrating this approach through a utility class (Configured).

<pre><code>public class ConfigPrinter extends Configured implements Tool {
 static {
 // by default core-site.xml is already added
 // loading "hdfs-site.xml" from classpath
 Configuration.addDefaultResource("hdfs-site.xml");
 Configuration.addDefaultResource("mapred-site.xml");
 }

 @Override
 public int run(String[] strings) throws Exception {
 Configuration config = this.getConf();
 for (Map.Entry&lt;String, String&gt; entry : config) {
 System.out.println(entry.getKey() + " = " + entry.getValue());
 }
 return 0;
 }

 public static void main(String[] args) throws Exception {
 ToolRunner.run(new ConfigPrinter(), args);
 }
}
</code></pre>

blocks|key|245769|text|您可以通过运行以下命令转储Hadoop配置：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|245770|$+hadoop+org.apache.hadoop.conf.Configuration|code-block|syntax|javascript|245771|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can dump Hadoop config by running:

<pre><code>$ hadoop org.apache.hadoop.conf.Configuration
</code></pre>

blocks|key|462358|text|从配置中获取特定密钥|type|unstyled|depth|inlineStyleRanges|entityRanges|data|462359|hdfs+getconf+-confKey+[key]

hdfs+getconf+-confKey+dfs.replication|code-block|syntax|javascript|462360|https://hadoop.apache.org/docs/r2.7.1/hadoop-project-dist/hadoop-hdfs/HDFSCommands.html#getconf|offset|length|462361|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|2N|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|T|8|@]|9|@$I|U|J|V|1|W]]|A|$]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|H]]]]

Gets a specific key from the configuration

<pre><code>hdfs getconf -confKey [key]

hdfs getconf -confKey dfs.replication
</code></pre>

<a href="https://hadoop.apache.org/docs/r2.7.1/hadoop-project-dist/hadoop-hdfs/HDFSCommands.html#getconf" rel="noreferrer">https://hadoop.apache.org/docs/r2.7.1/hadoop-project-dist/hadoop-hdfs/HDFSCommands.html#getconf</a>

blocks|key|245825|text|在另一个答案中使用了优秀的ConfigPrinter程序，我继续创建了一个可执行和可编译的版本。代码见https://github.com/tdunning/config-print。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|245826|要使用它，请将pom.xml文件中的hadoop版本更改为您想要的版本。然后这样做(你需要安装git、maven和java+)：|245827|$+git+clone+https://github.com/tdunning/config-print.git
Cloning+into+'config-print'...
remote:+Enumerating+objects:+13,+done.
remote:+Counting+objects:+100%25+(13/13),+done.
remote:+Compressing+objects:+100%25+(8/8),+done.
remote:+Total+13+(delta+1),+reused+12+(delta+0),+pack-reused+0
Unpacking+objects:+100%25+(13/13),+done.
$+cd+config-print/
$+mvn+-q+package
$+./target/config-printer+%7C+sort
log4j:WARN+No+appenders+could+be+found+for+logger+(org.apache.hadoop.util.Shell).
log4j:WARN+Please+initialize+the+log4j+system+properly.
log4j:WARN+See+http://logging.apache.org/log4j/1.2/faq.html#noconfig+for+more+info.
dfs.ha.fencing.ssh.connect-timeout+=+30000
file.blocksize+=+67108864
file.bytes-per-checksum+=+512
file.client-write-packet-size+=+65536
file.replication+=+1
file.stream-buffer-size+=+4096
fs.AbstractFileSystem.file.impl+=+org.apache.hadoop.fs.local.LocalFs
fs.AbstractFileSystem.ftp.impl+=+org.apache.hadoop.fs.ftp.FtpFs
fs.AbstractFileSystem.har.impl+=+org.apache.hadoop.fs.HarFs
fs.AbstractFileSystem.hdfs.impl+=+org.apache.hadoop.fs.Hdfs
fs.AbstractFileSystem.viewfs.impl+=+org.apache.hadoop.fs.viewfs.ViewFs
...+lots+of+stuff+deleted+...
s3native.stream-buffer-size+=+4096
s3.replication+=+3
s3.stream-buffer-size+=+4096
tfile.fs.input.buffer.size+=+262144
tfile.fs.output.buffer.size+=+262144
tfile.io.chunk.size+=+1048576
tdunning@nodea:~/config-print$+
$|code-block|syntax|javascript|245828|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/tdunning/config-print^0|1F|14|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

Using the excellent ConfigPrinter program in another answer, I went ahead and created an executable and compilable version. See <a href="https://github.com/tdunning/config-print" rel="nofollow noreferrer">https://github.com/tdunning/config-print</a> for the code.
To use this, change the hadoop version in the pom.xml file to whatever you us. Then do this (you will need git, maven and java installed):
<pre class="lang-sh prettyprint-override"><code>$ git clone https://github.com/tdunning/config-print.git
Cloning into 'config-print'...
remote: Enumerating objects: 13, done.
remote: Counting objects: 100% (13/13), done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 13 (delta 1), reused 12 (delta 0), pack-reused 0
Unpacking objects: 100% (13/13), done.
$ cd config-print/
$ mvn -q package
$ ./target/config-printer | sort
log4j:WARN No appenders could be found for logger (org.apache.hadoop.util.Shell).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
dfs.ha.fencing.ssh.connect-timeout = 30000
file.blocksize = 67108864
file.bytes-per-checksum = 512
file.client-write-packet-size = 65536
file.replication = 1
file.stream-buffer-size = 4096
fs.AbstractFileSystem.file.impl = org.apache.hadoop.fs.local.LocalFs
fs.AbstractFileSystem.ftp.impl = org.apache.hadoop.fs.ftp.FtpFs
fs.AbstractFileSystem.har.impl = org.apache.hadoop.fs.HarFs
fs.AbstractFileSystem.hdfs.impl = org.apache.hadoop.fs.Hdfs
fs.AbstractFileSystem.viewfs.impl = org.apache.hadoop.fs.viewfs.ViewFs
... lots of stuff deleted ...
s3native.stream-buffer-size = 4096
s3.replication = 3
s3.stream-buffer-size = 4096
tfile.fs.input.buffer.size = 262144
tfile.fs.output.buffer.size = 262144
tfile.io.chunk.size = 1048576
tdunning@nodea:~/config-print$ 
$
</code></pre>

I only find the way to set a property by <code>hadoop dfsadmin -D xx=yy</code> , 

but how do I find the value of a specific property <code>xx</code> in command line?

How do I print hadoop properties in command line?

Hadoop 

我只找到了通过hadoop dfsadmin -D xx=yy来设置属性的方法，但是如何在命令行中找到特定属性xx的值呢？

问如何在命令行中打印hadoop属性？
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