HDFS experiment (5) graphical Management

./ bin/hdfs dfsadmin -report

http://192.168.209.162:50070/dfshealth.html#tab-overview

You can manipulate directories

http://192.168.209.162:50070/explorer.html#/

Mode 1: Command Line Mode

Hadoop file operation command form is

hadoop fs -cmd

Description: cmd is a specific file operation command, is a variable number of parameters.

Hadoop's most commonly used file manipulation commands include adding files and directories, obtaining files, deleting files, etc.

1 Add files and directories

HDFS has a default working directory/usr/$USER, where $USER is your login username and the author's username is root. This directory cannot be created automatically and needs to be created by executing the mkdir command.

hadoop fs -mkdir /usr/root

Use the Hadoop command put to send the local file README.txt to HDFS.

hadoop fs -put README.txt .

Notice that the last argument to this command is a period (.), This means putting local files into the default working directory, which is equivalent to:

hadoop fs -put README.txt /user/root

2 Getting documents

Obtaining files includes two layers of meaning, one is HDFS obtains files from local files, that is, the added files described above; the other is local files obtain files from HDFS, you can use Hadoop's get command. For example, if the local file does not have a README.txt file and needs to be retrieved from HDFS, you can execute the following command.

hadoop fs -get README.txt .

or

hadoop fs -get README.txt /usr/root/README.txt

3 Delete files

Hadoop delete file command is rm. For example, to delete README.txt uploaded from a local file, execute the following command.

hadoop fs -rm README.txt

4 Retrieving documents

Retrieving a file is to look up the contents of a file in HDFS, using the cat command in hadoop. For example, to view the contents of README.txt, you can execute the following command.

hadoop fs -cat README.txt

In addition, the output of the cat command of hadoop can also be piped to the head of the Unix command:

hadoop fs -cat README.txt | head

Hadoop also supports the tail command to view the last kilobyte. For example, to look up the last kilobyte of README.txt, you can execute the following command.

hadoop fs -tail README.txt

5 See Help

Check out the Hadoop Command Help, which allows us to master and use Hadoop commands well. We can run hadoop fs to get a complete command line for the version of Hadoop we are using, or we can use help to show the usage and short description of a specific command.

For example, to understand the ls command, execute the following command.

hadoop fs -help ls