vim /etc/profile.d/hadoop
export HDFS_NAMENODE_USER=root
export HDFS_DATANODE_USER=root
export HDFS_SECONDARYNAMENODE_USER=root
export YARN_RESOURCEMANAGER_USER=root
export YARN_NODEMANAGER_USER=root
​
export PATH=/opt/hadoop/sbin:/opt/hadoop/bin:$PATH

127.0.0.1       localhost
192.168.56.11   hadoop-1        debian1
192.168.56.12   hadoop-2        debian2
192.168.56.13   hadoop-3        debian3

<configuration>
    <property>
        <name>dfs.datanode.data.dir</name>
        <value>file:///opt/hadoop/data/datanode</value>
    </property>
    <property>
        <name>dfs.namenode.name.dir</name>
        <value>file:///opt/hadoop/data/namenode</value>
    </property>
    <property>
        <name>dfs.namenode.http-address</name>
        <value>hadoop-1:50070</value>
    </property>
    <property>
        <name>dfs.namenode.secondary.http-address</name>
        <value>hadoop-1:50090</value>
    </property>
    <!-- 不开启文件权限控制 -->
    <property>
      <name>dfs.permissions</name>
      <value>false</value>
    </property>
</configuration>

<configuration>
    <property>
        <name>fs.defaultFS</name>
        <value>hdfs://hadoop-1:9000</value>
    </property>
</configuration>

<configuration>
    <property>
        <name>yarn.nodemanager.aux-services</name>
        <value>mapreduce_shuffle</value>
    </property>
    <property>
        <name>yarn.nodemanager.aux-services.mapreduce_shuffle.class</name>
        <value>org.apache.hadoop.mapred.ShuffleHandler</value>
    </property>
    <property>
        <name>yarn.resourcemanager.resource-tracker.address</name>
        <value>hadoop-1:8025</value>
    </property>
    <property>
        <name>yarn.resourcemanager.scheduler.address</name>
        <value>hadoop-1:8030</value>
    </property>
    <property>
        <name>yarn.resourcemanager.address</name>
        <value>hadoop-1:8050</value>
    </property>
</configuration>

/opt/hadoop/sbin/start-all.sh

<dependency>
    <groupId>org.apache.hadoop</groupId>
    <artifactId>hadoop-client</artifactId>
    <version>3.2.1</version>
</dependency>

static FileSystem getFileSystem() throws IOException, URISyntaxException {
    URI uri = new URI("hdfs://localhost:9000/");
    // 使用HDFS文件系统并提供服务器路径，端口号在core-site.xml中配置
    return org.apache.hadoop.fs.FileSystem.get(uri, new Configuration());
}