HDFS in the third step of hadoop development

Operate on hdfs:

 Note: The namenode needs to be formatted before opening hdfs and yarn, otherwise the namenode will not be turned on

 which is:

hadoop namenode -format #Format first, sometimes you need to agree to something in the middle, that is, y agree
start-yarn.sh #start-all.sh is deprecated, but can also be used
start-dfs.sh

Use jps to check whether namenode and datanode are all enabled

hadoop fs -mkdir /input #Create input directory on hdfs
echo "hello adu hello world"> file #Create a local file
hadoop fs -put file /input #Upload to hdfs

You can view the status of hdfs at localhost:50070 (browse the file system in utilities on the upper right side of the page)

The content of pom.xml in idea:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>hadoop</groupId>
    <artifactId>com.adu</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-client</artifactId>
            <version>2.7.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-common</artifactId>
            <version>2.7.2</version>
        </dependency>
        <dependency>
            <groupId>org.apache.hadoop</groupId>
            <artifactId>hadoop-hdfs</artifactId>
            <version>2.7.2</version>
        </dependency>
    </dependencies>
    <repositories>
        <repository>
            <id>apache</id>
            <url>http://maven.apache.org</url>
        </repository>
    </repositories>
    <build>
        <plugins>
            <plugin>
                <artifactId>maven-dependency-plugin</artifactId>
                <configuration>
                    <excludeTransitive>false</excludeTransitive>
                    <stripVersion>true</stripVersion>
                    <outputDirectory>./lib</outputDirectory>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

The map and reduce functions are the same as in the previous chapters

Click on run""edit configurations

Change program arguments to: hdfs://localhost:9000/input/file hdfs://localhost:9000/output

Others are the same as the previous chapter, there is a space between the above two directories, and the output directory does not need to be created by itself, the file file is the uploaded file