[Solved] hadoop Error: 9000 failed on connection exception java.net.ConnectException Denied to Access

To view the files on haddop, enter:

hadoop fs -ls /

The following occurred:

ls: Call From yx/127.0.1.1 to 0.0.0.0:9000 failed on connection exception: 
java.net.ConnectException: Denied to Access 
For more details see:  http://wiki.apache.org/hadoop/ConnectionRefused

Display 9000 port access denied
from the configuration file, you can know that Hadoop needs to access the machine through 9000 port, but now 9000 port access is denied
Input:

telnet localhost 9000

Display:

Trying 127.0.0.1…
telnet: Unable to connect to remote host: Connection refused

Input:

nmap -p 9000 localhost

Display:

Starting Nmap 7.80 ( https://nmap.org ) at 2020-04-25 14:57 CST
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000051s latency).
PORT STATE SERVICE
9000/tcp closed cslistener
Nmap done: 1 IP address (1 host up) scanned in 0.03 seconds

 

Use the command:

 lsof -i :9000

See which app is using the port. If the result is empty (return value 1), it is not opened
the above is just to check the status and will not change anything.

Because hadoop connects to the local port in core-site.xml
Open $HADOOP_HOME/etc/hadoop/core-site.xml

<configuration>
<property>
    <name>hadoop.tmp.dir</name>
    <value>/data/tmp/hadoop/tmp</value>
</property>
<property>
    <name>fs.defaultFS</name>
    <value>hdfs://0.0.0.0:9000</value>
</property>
</configuration>

It is found that I have not configured the port number, which is modified to:
hdfs://localhost:9000
It still not work.
I tried many methods, and finally found that the most commonly used method on the Internet is to use this method, which is really OK:

cd $HADOOP_HOME/bin
hdfs namenode -format

But I still couldn’t run it. I tried many times and all the results were the same. Later, then I found an error:

WARN common.Util: Path /data/tmp/hadoop/hdfs/name should be specified as a URI in configuration files. Please update hdfs configuration.

This is due to the non-standard path. The file describing the path is in:

$HADOOP_HOMW/etc/hadoop/hdfs-site.xml

Place in the file:

 <property>  
     <name>dfs.datanode.data.dir</name>  
     <value>/data/tmp/hadoop/hdfs/data</value>  
 </property>

Amend to read:

  <property>  
     <name>dfs.datanode.data.dir</name>  
     <value>file:///data/tmp/hadoop/hdfs/data</value>  
 </property>

The warning disappears
but this does not play a decisive role. My reason is that the security mode is turned on. Just turn off the security mode

cd $HADOOP_HOME/bin
hadoop dfsadmin -safemode leave

Users can

hadoop dfsadmin -safemode value

Operation security mode
value value:
enter: enter security mode
leave: force to leave security mode
get: return to security mode status
wait: until the end of security mode
now:

[email protected]:/apps/hadoop/bin# hadoop fs -ls /
20/04/25 19:24:24 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Found 1 items
drwxr-xr-x   - root supergroup          0 2020-04-25 17:13 /test

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