In this tutorial, we will walk through many of the common of the basic Hadoop Distributed File System (HDFS) commands you will need to manage files on HDFS. The particular datasets we will utilize to learn HDFS file management are San Francisco salaries from 2011-2014.
We will download sf-salaries-2011-2013.csv and sf-salaries-2014.csv data onto our local filesystems of the sandbox. The commands are tailored for mac and linux users.
1. Open a terminal on your local machine, SSH into the sandbox:
ssh email@example.com -p 2222
Note: If your on VMware or Azure, insert your appropriate ip address in place of 127.0.0.1. Azure users will need to replace port 2222 with 22.
2. Copy and paste the commands to download the sf-salaries-2011-2013.csv and sf-salaries-2014.csv files. We will use them while we learn file management operations.
# download sf-salaries-2011-2013 wget https://raw.githubusercontent.com/hortonworks/tutorials/hdp/assets/using-the-command-line-to-manage-hdfs/sf-salary-datasets/sf-salaries-2011-2013.csv # download sf-salaries-2014 wget https://raw.githubusercontent.com/hortonworks/tutorials/hdp/assets/using-the-command-line-to-manage-hdfs/sf-salary-datasets/sf-salaries-2014.csv
Let’s learn by writing the syntax. You will be able to copy and paste the following example commands into your terminal. Let’s login under hdfs user, so we can give root user permission to perform file operations:
su hdfs cd
We will use the following command to run filesystem commands on the file system of hadoop:
hdfs dfs [command_operation]
Refer to the File System Shell Guide to view various command_operations.
hdfs dfs -chmod 777 /user
Type the following command, so we can switch back to the root user. We can perform the remaining file operations under the user folder since the permissions were changed.
# Usage: # hdfs dfs -mkdir <paths> # Example: hdfs dfs -mkdir /user/hadoop hdfs dfs -mkdir /user/hadoop/sf-salaries-2011-2013 /user/hadoop/sf-salaries /user/hadoop/sf-salaries-2014
# Usage: # hdfs dfs -put <local-src> ... <HDFS_dest_path> # Example: hdfs dfs -put sf-salaries-2011-2013.csv /user/hadoop/sf-salaries-2011-2013/sf-salaries-2011-2013.csv hdfs dfs -put sf-salaries-2014.csv /user/hadoop/sf-salaries-2014/sf-salaries-2014.csv
# Usage: # hdfs dfs -ls <args> # Example: hdfs dfs -ls /user/hadoop hdfs dfs -ls /user/hadoop/sf-salaries-2011-2013 hdfs dfs -ls /user/hadoop/sf-salaries-2011-2013/sf-salaries-2011-2013.csv
# Usage: # hdfs dfs -du URI # Example: hdfs dfs -du /user/hadoop/ /user/hadoop/sf-salaries-2011-2013/sf-salaries-2011-2013.csv
# Usage: # hdfs dfs -get <hdfs_src> <localdst> # Example: hdfs dfs -get /user/hadoop/sf-salaries-2011-2013/sf-salaries-2011-2013.csv /home/
# Usage: # hdfs dfs -getmerge <src> <localdst> [addnl] # hdfs dfs -getmerge <src1> <src2> <localdst> [addnl] # Option: # addnl: can be set to enable adding a newline on end of each file # Example: hdfs dfs -getmerge /user/hadoop/sf-salaries-2011-2013/ /user/hadoop/sf-salaries-2014/ /root/output.csv
Merges the files in sf-salaries-2011-2013 and sf-salaries-2014 to output.csv in the root directory of the local filesystem. The first file contained about 120,000 rows and the second file contained almost 30,000 rows. This file operation is important because it will save you time from having to manually concatenate them.
# Usage: # hdfs dfs -cp <src-url> <dest-url> # Example: hdfs dfs -cp /user/hadoop/sf-salaries-2011-2013/ /user/hadoop/sf-salaries-2014/ /user/hadoop/sf-salaries
-cp: copies sf-salaries-2011-2013, sf-salaries-2014 and all their contents to sf-salaries
Verify the files or directories successfully copied to the destination folder:
hdfs dfs -ls /user/hadoop/sf-salaries/ hdfs dfs -ls /user/hadoop/sf-salaries/sf-salaries-2011-2013 hdfs dfs -ls /user/hadoop/sf-salaries/sf-salaries-2014
Visual result of distcp file operation. Notice that both src1 and src2 directories and their contents were copied to the dest directory.
Help command opens the list of commands supported by Hadoop Data File System (HDFS)
# Example: hdfs dfs -help
Hope this short tutorial was useful to get the basics of file management.
Congratulations! We just learned to use commands to manage our sf-salaries-2011-2013.csv and sf-salaries-2014.csv dataset files in HDFS. We learned to create, upload and list the the contents in our directories. We also acquired the skills to download files from HDFS to our local file system and explored a few advanced features of HDFS file management using the command line.
In the previous tutorial, we learned to manage files on the Hadoop Distributed File System (HDFS) with the command line. Now we will use Ambari Files View to perform many of the file management operations on HDFS that we learned with CLI, but through the web-based interface.
We will download sf-salaries-2011-2013.csv and sf-salaries-2014.csv data onto our local filesystems of our computer. The commands are tailored for mac and linux users.
1. Open a terminal on your local machine, copy and paste the commands to download the sf-salaries-2011-2013.csv and sf-salaries-2014.csv files. We will use them while we learn file management operations.
cd ~/Downloads # download sf-salaries-2011-2013 wget https://raw.githubusercontent.com/hortonworks/tutorials/hdp/assets/using-the-command-line-to-manage-hdfs/sf-salary-datasets/sf-salaries-2011-2013.csv # download sf-salaries-2014 wget https://raw.githubusercontent.com/hortonworks/tutorials/hdp/assets/using-the-command-line-to-manage-hdfs/sf-salary-datasets/sf-salaries-2014.csv mkdir sf-salary-datasets mv sf-salaries-2011-2013.csv sf-salaries-2014.csv sf-salary-datasets/
1. Login to Ambari Interface at
127.0.0.1:8080. Use the following login credentials in Table 1.
Table 1: Ambari Login credentials
Ambari password setup process, refer to step 2.2 Setup Ambari Admin Password Manually of Learning the Ropes of the Hortonworks Sandbox.
2. Now that we have admin privileges, we can manage files on HDFS using Files View. Hover over the Ambari Selector Icon , enter the Files
The Files View Interface will appear with the following default folders.
3. We will create 4 folders using the Files View web-interface. All three folders: sf-salaries-2011-2013, sf-salaries and sf-salaries-2014 will reside in the hadoop folder, which resides in user. Navigate into the user folder. Click the new folder button , an add new folder window appears and name the folder
hadoop. Press enter or Add
4. Navigate into the hadoop folder. Create the three folders: sf-salaries-2011-2013, sf-salaries and sf-salaries-2014 following the process stated in the previous instruction.
We will upload two files from our local machine: sf-salaries-2011-2013.csv and sf-salaries-2014.csv to appropriate HDFS directories.
1. Navigate through the path
/user/hadoop/sf-salaries-2011-2013 or if you’re already in hadoop, enter the sf-salaries-2011-2013 folder. Click the upload button to transfer sf-salaries-2011-2013.csv into HDFS.
An Upload file window appears:
2. Click on the cloud with an arrow. A window with files from your local machine appears, find sf-salaries-2011-2013.csv in the Downloads/sf-salary-datasets folder, select it and then press open button.
3. In Files View, navigate to the hadoop folder and enter the sf-salaries-2014 folder. Repeat the upload file process to upload sf-salaries-2014.csv.
Each time we open a directory, the Files View automatically lists the contents. Earlier we started in the user directory.
1. Let’s navigate back to the user directory to examine the details given by the contents. Reference the image below while you read the Directory Contents Overview.
/ Directory Contents Overview of Columns
In the command line when the directories and files are listed with the
hadoop fs -du /user/hadoop/, the size of the directory and file is shown. In Files View, we must navigate to the file to see the size, we are not able to see the size of the directory even if it contains files.
1. Let’s view the size of sf-salaries-2011-2013.csv file. Navigate through
/user/hadoop/sf-salaries-2011-2013. How much space has the file utilized? Files View shows 11.2 MB for sf-salaries-2011-2013.csv.
Files View enables users to download files and folders to their local machine with ease.
1. Let’s download the sf-salaries-2011-2013.csv file to our computer. Click on the file’s row, the row’s color becomes blue, a group of file operations will appear, select the Download button. The default directory the file downloads to is our Download folder on our local machine.
File Concatenation merges two files together. If we concatenate sf-salaries-2011-2013.csv with sf-salaries-2014.csv, the data from sf-salaries-2014.csv will be appended to the end of sf-salaries-2011-2013.csv. A typical use case for a user to use this feature is when they have similar large datasets that they want to merge together. The manual process to combine large datasets is inconvenient, so file concatenation was created to do the operation instantly.
1. Before we merge the csv files, we must place them in the same folder. Click on sf-salaries-2011-2013.csv row, it will highlight in blue, then press copy and in the copy window appears, select the sf-salaries-2014 folder and press Copy to copy the csv file to it.
2. We will merge two large files together by selecting them both and performing concatenate operation. Navigate to the sf-salaries-2014 folder. Select sf-salaries-2011-2013.csv, hold shift and click on sf-salaries-2014.csv. Click the concatenate button. The files will be downloaded into the Download folder on your local machine.
3. By default, Files View saves the merged files as a txt file, we can open the file and save it as a csv file. Then open the csv file and you will notice that all the salaries from 2014 are appended to the salaries from 2011-2013.
Copy file or directories recursively means all the directory’s files and subdirectories to the bottom of the directory tree are copied. For instance, we will copy the hadoop directory and all of its contents to a new location within our hadoop cluster. In production, the copy operation is used to copy large datasets within the hadoop cluster or between 2 or more clusters.
1. Navigate to the user directory. Click on the row of the hadoop directory. Select the Copy button .
2. The Copy to window will appear. Select the tmp folder, the row will turn blue. If you select the folder icon, the contents of tmp become visible. Make sure the row is highlighted blue to do the copy. Click the blue Copy button to copy the hadoop folder recursively to this new location.
3. A new copy of the hadoop folder and all of its contents can be found in the tmp folder. Navigate to tmp for verification. Check that all of the hadoop folder’s contents copied successfully.
Congratulations! We just learned to use the Files View to manage our sf-salaries-2011-2013.csv and sf-salaries-2014.csv dataset files in HDFS. We learned to create, upload and list the the contents in our directories. We also acquired the skills to download files from HDFS to our local file system and explored a few advanced features of HDFS file management.