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Exercise 1 Hadoop and HDFS

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ISIT312 Big Data Management
Exercise 1
Hadoop and HDFS
In this exercise, you will get familiar with using the Linux Shell and Zeppelin to interact with
Hadoop.
DO NOT attempt to copy the Linux commands in this document to your working Terminal, because
it is error-prone. Type those commands by yourself.
Laboratory Instructions.
First you must install download and install VirtualBox on your system.
You can download VirtualBox from here:
https://www.virtualbox.org/wiki/Downloads
You can find installation procedure here:
https://documents.uow.edu.au/~jrg/115/cookbook/e1-1-A1-frame.html
Connect to Moodle and to download ova image of virtual machine use a link
Image of Virtual Machine for ISIT312
available in WEB LINKS section.
When downloaded start VirtualBox and use option File->Import to import a file BigDataVM07-SEP-2020.ova into VirtualBox.
After the importation is completed, a VM named BigDataVM-07-SEP-2020 appears in a
column on the left-hand side of VirtualBox window. Use Settings option and later on System
option and allow the virtual machine to use all available Base Memory on the “green side” of a
scale. In Display option grant to the virtual machine all available Video Memory. Finally, in
Network option, check (if necessary, and change) the Attached to option to NAT.
Use Start option to run BigDataVM-07-SEP-2020.
Note. There is no need for user name and password.
Note. Next time you use the VM a process of changing Settings does not need to be repeated.
(1) Start Shell and Zeppelin
Start a Shell window with Ctrl + Alt + T or use the second from bottom icon in a sidebar on
the left-hand side of a screen.
You can use the Linux Shell to interact with Hadoop. However, it is recommended that you use
Zeppelin, which provides a better interface. To start Zeppelin, enter in the Shell window:
$ZEPPELIN_HOME/bin/zeppelin-daemon.sh start
Then use the fourth from bottom icon in the sidebar to start the Firefox browser and use access the
following link.
127.0.0.1:8080
You may need to refresh the browser until you see the following information:
Then, use a link Create new note to create a new note and named it as, say, Lab1. At the
moment you can use sh as a default interpreter. Do not create any folders and click at Create
button to create a note.
A note comprises of many paragraphs. In the first line of each paragraph, you need to indicate the
interpreter by inputting %<interpreter> where a metasymbol <interpreter> should be replaced with
interpreter name. In this laboratory class, we use the Shell interpreter with command is %sh. Type
%sh
pwd
inside a note window (see a picture below). We would like to process pwd command (print working
directory) in the Shell window.
When you are ready to run your code in a Zeppelin paragraph, click the Run button (a small triangle
next to READY text on the right -hand side of a note window) or use Shift + Return keyboard
shortcut.
Zeppelin processes pwd command in the Shell window and displays a text:
/home/bigdata
You can also try to use the Markdown interpreter to write down some text.
For example, type the following lines inside Zeppelin paragraph.
%md
<b>Hello</b>, <i>Hello</i>, Hello !!!
Can you guess from the outcomes what does Markdown do ?
It is always possible top re-edit the contents of Zeppelin’s paragraphs and re-run a new code many
times. If you do not provide a name of interpreter, for example %sh or %md then Zeppelin uses a
default interpreter that has been determined as %sh when we created a new note.
Now you can interact with Hadoop.
(2) Hadoop files and scripts
Have a look at what are contained in the $HADOOP_HOME. Type and process the following lines one
by one in the separate Zeppelin’s paragraphs.
ls $HADOOP_HOME # view the root directory
ls $HADOOP_HOME/bin # view the bin directory
ls $HADOOP_HOME/sbin # view the sbin directory
Note that # denotes a start of inline comment and ls is a Shell command that list the contents of a
folder. In another paragraph try the following command to learn what does $HADOOP_HOME mean.
echo $HADOOP_HOME
The bin and sbin folders contain scripts for Hadoop.
(3) Hadoop Initialization
Now you can start all Hadoop processes. First, start HDFSNameNode and DataNode processes.
$HADOOP_HOME/sbin/hadoop-daemon.sh start namenode
$HADOOP_HOME/sbin/hadoop-daemon.sh start datanode
Next, start YARN ResourceManager and NodeManager.
$HADOOP_HOME/sbin/yarn-daemon.sh start resourcemanager
$HADOOP_HOME/sbin/yarn-daemon.sh start nodemanager
Finally, start the Job History Server.
$HADOOP_HOME/sbin/mr-jobhistory-daemon.sh start historyserver
To view the running daemon processes the following command.
jps
The following Hadoop processes should be listed (note that the process numbers may be different).
2897 JobHistoryServer
2993 Jps
2386 NameNode
2585 ResourceManager
2654 NodeManager
2447 DataNode
(4) HDFS Shell commands
Create a folder myfolder in HDFS process the following command.
$HADOOP_HOME/bin/hadoop fs -mkdir myfolder
To check if the folder has been created process the following command.
$HADOOP_HOME/bin/hadoop fs -ls
Copy a file from the local filesystem to HDFS. The following command copy all files with the .txt
extension in $HADOOP_HOME to a folder myfolder in HDFS:
$HADOOP_HOME/bin/hadoop fs -put $HADOOP_HOME/*.txt myfolder
To verify the results, list all *.txt files in $HADOOP_HOME.
ls $HADOOP_HOME/*.txt
Next, list the files in myfolder folder in HDFS:
$HADOOP_HOME/bin/hadoop fs -ls myfolder
To view a file in HDFS process the following command.
$HADOOP_HOME/bin/hadoop fs -cat myfolder/README.txt
Copy a file from HDFS to the Desktop folder in a local filesystem process the following command.
$HADOOP_HOME/bin/hadoop fs -copyToLocal myfolder/README.txt /home/bigdata/Desktop
To verify the results, process the following command.
ls /home/bigdata/Desktop
To remove a file README.txt from HDFS process the following command.
$HADOOP_HOME/bin/hadoop fs -rm myfolder/README.txt
(5) HDFS user interface
Open another tab in the Firefox Web Browser, and use a link localhost:50070.
You will see localhost:8020. This is the location of the HDFS. It is specified in a configuration
file named core-site.xml.
Check this file in a folder $HADOOP_HOME/etc/hadoop, that contains Hadoop’s configuration
files.
Process the following Shell command to view the contents of a file core-site.xml in Zeppelin
paragraph.
cat $HADOOP_HOME/etc/hadoop/core-site.xml
Return to and browse the Web user interface, for example, you can see the location of the
Datanode. Use the options Utilities and then Browser the file system. Check the
.txt files uploaded to HDFS previously. Note that the root directory of bigdata is in the user
directory.
To view all root folders in HDFS in Terminal, you can also enter the following command in a new
Zeppelin paragraph.
$HADOOP_HOME/bin/hadoop fs -ls /
(6) HDFS’s Java Interface
A Java program listed below retrieves the contents of a file in the HDFS. This program is equivalent
to a command hadoop fs -cat. A source code of the program (FileSystemCat.java) is
available in exercise-1 folder and it is also provided below. Read and understand the source
code.
// cc FileSystemCat
// Displays files from a Hadoop filesystem on standard output
// by using the FileSystem directly
import java.io.InputStream;
import java.net.URI;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
// vv FileSystemCat
public class FileSystemCat {
public static void main(String[] args) throws Exception {
String uri = args[0];
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(URI.create(uri), conf);
InputStream in = null;
try {
in = fs.open(new Path(uri));
IOUtils.copyBytes(in, System.out, 4096, false);
} finally {
IOUtils.closeStream(in);
}
}
}
// ^^ FileSystemCat
Now, create a file FileSystemCat.java with the source code and try to compile it. It is
important that all commands must be processed in the same Zeppelin paragraph. First, use the
following command to define environment variable HADOOP_CLASSPATH.
export HADOOP_CLASSPATH=$($HADOOP_HOME/bin/hadoop classpath)
This environment variable points to all basic Hadoop libraries. Note that each time of open the
Terminal and you want to use the environment variable then you must export it. To view the
libraries, process in the same Zeppelin paragraph the following command.
echo $HADOOP_CLASSPATH
Now, make sure that the file FileSystemCat.java is in your current folder. Now, compile the
program and create jar file in the following way (still in the same Zeppelin paragraph).
javac -cp $HADOOP_CLASSPATH FileSystemCat.java
jar cvf FileSystemCat.jar FileSystemCat*.class
The first above command above moves to the current folder that contains the Java source (so that
the compilation does not create any package namespace for the main class). The second command
compiles the source code. The last command creates a jar file that includes the Java class(es).
Now, you can run the jar file by using the hadoop script and jar command (still in the same
Zeppelin paragraph).
$HADOOP_HOME/bin/hadoop jar /home/bigdata/Desktop/FileSystemCat.jar FileSystemCat myfolder/LICENSE.txt
Check whether the uploaded file is same as the local file.
(7) Shut down Hadoop
When finishing your practice with Hadoop, it is good practice to terminate the Hadoop daemons
before turning off the VM.
Use the following command to terminate the Hadoop daemons.
$HADOOP_HOME/sbin/hadoop-daemon.sh stop namenode
$HADOOP_HOME/sbin/hadoop-daemon.sh stop datanode
$HADOOP_HOME/sbin/yarn-daemon.sh stop resourcemanager
$HADOOP_HOME/sbin/yarn-daemon.sh stop nodemanager
$HADOOP_HOME/sbin/mr-jobhistory-daemon.sh stop historyserver
(8) Make a typescript of information in Terminal
If you work in Shell but not Zeppelin, you can use the script command to make a typescript of
everything printed in your Terminal.
script a-file-name-you-want-to-save-the-typescript-to.txt
<work with your Terminal..>
exit
Check the contents of a-file-name-you-want-to-save-the-typescript-to.txt.
It is good idea to export Zeppelin note, such that you can import it before the next exercise and
reuse the commands processed up to now.
End of Exercise 1

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