Using the command line to manage files on HDFS
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In this tutorial we will walk through some of the basic HDFS commands you will need to manage files on HDFS. To complete this tutorial you will need a working HDP cluster. The easiest way to have a Hadoop cluster is to download the Hortonworks Sandbox.
Let’s get started.
Let’s look at the syntax first:
- It will take path uri’s as argument and creates directory or directories.
Usage: hadoop fs -mkdir <paths> Example: hadoop fs -mkdir /user/hadoop/dir1 /user/hadoop/dir2 hadoop fs -mkdir hdfs://nn1.example.com/user/hadoop/dir
- Lists the contents of a directory
- For a file returns stats of a file
Usage: hadoop fs -ls <args> Example: hadoop fs -ls /user/hadoop/dir1 /user/hadoop/dir2 hadoop fs -ls /user/hadoop/dir1/filename.txt hadoop fs -ls hdfs://<hostname>:9000/user/hadoop/dir1/
Let’s use the following commands as follows and execute. You can ssh to the sandbox using Tools like Putty. You could download putty.exe from the internet.
Let’s touch a file locally.
$ touch filename.txt
- Displays sizes of files and directories contained in the given directory or the size of a file if its just a file.
Usage: hadoop fs -du URI Example: hadoop fs -du /user/hadoop/ /user/hadoop/dir1/Sample.txt
Now let’s see how to upload and download files from and to Hadoop Data File System(HDFS)
Upload: ( we have already tried this earlier)
- Copy single src file, or multiple src files from local file system to the Hadoop data file system
Usage: hadoop fs -put <localsrc> ... <HDFS_dest_Path> Example: hadoop fs -put /home/ec2-user/Samplefile.txt ./ambari.repo /user/hadoop/dir3/
hadoop fs -get:
- Copies/Downloads files to the local file system
Usage: hadoop fs -get <hdfs_src> <localdst> Example: hadoop fs -get /user/hadoop/dir3/Samplefile.txt /home/
- Takes a source directory files as input and concatenates files in src into the destination local file.
Usage: hadoop fs -getmerge <src> <localdst> [addnl] Example: hadoop fs -getmerge /user/hadoop/dir1/ ./Samplefile2.txt Option: addnl: can be set to enable adding a newline on end of each file
- Copy file or directories recursively
- It is a tool used for large inter/intra-cluster copying
- It uses MapReduce to effect its distribution copy, error handling and recovery, and reporting
Usage: hadoop distcp <srcurl> <desturl> Example: hadoop distcp hdfs://<NameNode1>:8020/user/hadoop/dir1/ \ hdfs://<NameNode2>:8020/user/hadoop/dir2/
You could use the following steps to perform getmerge and discp.
Let’s upload two files for this exercise first:
# touch txt1 txt2 # hadoop fs -put txt1 txt2 /user/hadoop/dir2/ # hadoop fs -ls /user/hadoop/dir2/
You can use Help command to get list of commands supported by Hadoop Data File System(HDFS)
Example: hadoop fs -help
Hope this short tutorial was useful to get the basics of file management.