无法在hadoop 3.2.1上执行hadoop jar命令：连接异常失败：java.net.ConnectException:连接被拒绝；

我已经在Virtualbox上的Ubuntu20.04中安装了Hadoop 3.2.1，用于我的大学学习和大学截止日期，所以我是Hadoop新手。我在网上搜索了几个关于如何在Hadoop上mapreduce的源代码

但是，当我在终端上键入时：

hadoop jar '/home/tamminen/WordCountTutorial/firstTutorial.jar' WordCount /WordCountTutorial/Input /WordCountTutorial/Output

格式：

hadoop jar <JAR_FILE> <CLASS_NAME> <HDFS_INPUT_DIRECTORY> <HDFS_OUTPUT_DIRECTORY>

这让我陷入了hadoop dfs-cat做不到的境地*

这是我的hadoop配置文件，我做了如下更改：

2020-10-11 18:59:04,584 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 0 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:05,595 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 1 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:06,598 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 2 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:07,618 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 3 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:08,619 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 4 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:09,621 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 5 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:10,624 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 6 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:11,625 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 7 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:12,627 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 8 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:13,629 INFO ipc.Client: Retrying connect to server: localhost/127.0.0.1:8032. Already tried 9 time(s); retry policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=10, sleepTime=1000 MILLISECONDS)
2020-10-11 18:59:13,632 INFO retry.RetryInvocationHandler: java.net.ConnectException: Call From 18k10018-data-mining/10.0.2.15 to localhost:8032 failed on connection exception: java.net.ConnectException: Connection refused; For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused, while invoking ApplicationClientProtocolPBClientImpl.getNewApplication over null after 3 failover attempts. Trying to failover after sleeping for 34444ms.

core-site.xml

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://localhost:9000</value>
    </property>
    <property>
        <name>hadoop.proxyuser.dataflair.groups</name>
        <value>*</value>
    </property>
    <property>
        <name>hadoop.proxyuser.dataflair.hosts</name>
        <value>*</value>
    </property>
    <property>
        <name>hadoop.proxyuser.server.hosts</name>
        <value>*</value>
    </property>
    <property>
        <name>hadoop.proxyuser.server.groups</name>
    <value>*</value>
    </property>
</configuration> 

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谁能解释一下为什么会出现这种错误，并给我一个解决方案我应该怎么做hadoop jar？

这可能会发生，因为有时hadoop会在服务器的内部IP地址而不是本地主机或127.0.0.1上启动一些服务。您可以尝试在所有Hadoop配置文件中将127.0.0.1更改为服务器的实际IP地址，并查看它是否有效。另一种方法是以root用户身份编辑/etc/hosts文件，并将localhost映射到服务器的实际ip

有关更精确的说明，请参见下面的文章，

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如果您运行

jps

，纱线是否正在运行？我认为没有，只有3206 DataNode、15415 jps、3468 SecondaryNameNode和3055 NameNode可以解释连接纱线时出现的错误，然后。我假设您运行了

start-thread

？首先，我没有运行start-thread，然后在您建议我运行start-thread之后，我尝试运行start-thread。因此，当我运行jps时，终端显示如下：29025节点管理器3206数据节点28824资源管理器29192 jps 3468 SecondaryNameNode 3055 NameNode。但是当我执行hadoop jar命令时，该命令仍然如下所示：java.net.ConnectException:Connection-seeded；有关更多详细信息，请参阅：，同时在5次故障切换尝试后通过null调用ApplicationClientProtocolPBClientImpl.getNewApplication。尝试在睡眠42681ms后进行故障切换。您是否阅读了该链接中的建议？

<configuration>
    <property>
        <name>dfs.replication</name>
        <value>1</value>
    </property>
</configuration>

<configuration>
    <property>
        <name>mapreduce.framework.name</name>
        <value>yarn</value>
    </property>
    <property>
        <name>mapred.child.java.opts</name>
        <value>-Xmx4096m</value>
    </property>
    <property>
        <name>mapreduce.application.classpath</name>
        <value>$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/*:$HADOOP_MAPRED_HOME/share/hadoop/mapreduce/lib/*</value>
    </property>
</configuration>

<configuration>
    <property>
        <name>yarn.nodemanager.aux-services</name>
        <value>mapreduce_shuffle</value>
    </property>
    <property>
        <name>yarn.resourcemanager.address</name>
        <value>127.0.0.1:8032</value>
    </property>
    <property>
        <name>yarn.resourcemanager.scheduler.address</name>
        <value>127.0.0.1:8030</value>
    </property>
    <property>
        <name>yarn.resourcemanager.resource-tracker.address</name>
        <value>127.0.0.1:8032</value>
    </property>
    <property>
        <name>yarn.nodemanager.env-whitelist</name>
        <value>JAVA_HOME,HADOOP_COMMON_HOME,HADOOP_HDFS_HOME,HADOOP_CONF_DIR,CLASSPATH_PREPEND_DISTCACHE,HADOOP_YARN_HOME,HADOOP_MAPRED_HOME</value>
    </property>
</configuration>

...
# Extra Java runtime options for all Hadoop commands. We don't support
# IPv6 yet/still, so by default the preference is set to IPv4.
# export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true"
export HADOOP_OPTS="-Xmx5096m"  --> Only this I added from searching hadoop tutorial solution beside of JAVA_HOME
# For Kerberos debugging, an extended option set logs more information
# export HADOOP_OPTS="-Djava.net.preferIPv4Stack=true -Dsun.security.krb5.debug=true -Dsun.security.spnego.debug"
...