Change desktop screen size using terminal linux inside VM

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Change desktop screen size using terminal linux inside VM

xrandr -s 1440x900

xrandr -s <Resolution which you want to change>

you can use

xrandr --verbose 

option to get the available screen resolution available.

Option with xrandr :

Install GNOME Desktop Ubuntu

Using following command we can install and enable desktop GUI for Ubuntu server version if needed.


sudo apt-get install ubuntu-gnome-desktop
sudo service gdm restart

org.apache.hadoop.yarn.exceptions.InvalidAuxServiceException: The auxService:mapreduce_shuffle does not exist

Add following entries to yarn-site.xml if not present and restar yarn service.


<property>
<name>yarn.nodemanager.aux-services</name>
<value>mapreduce_shuffle</value>
</property>


<property>
<name>yarn.nodemanager.aux-services.mapreduce_shuffle.class</name>
<value>org.apache.hadoop.mapred.ShuffleHandler</value>
</property>

Enable passwordless sudoers for a user

We can add following line in /etc/sudoers to enable the user to be passwordless login from other machines.


<username>  ALL=(ALL:ALL) NOPASSWD: ALL

Comparison between RDBMS and Map-Reduce

	RDBMS	Map-Reduce
Scalability	Scale UP	Scale Out
Data Size	GB	PB and more
Read/Write	Batch and Interactive	Batch
Update Type	Write many Read many	Write once Read many
Integrity	High	Low
Structure	Structural data/ Schema first Write later	Non Structural data/ Write first Schema later
Query	SQL	No SQL and SQL support too with add on tools
Response time	Faster for Less data/ slow once size increases	Faster for more data in comparison
Note: Slowly with the new sub projects being developed for Hadoop this gap is being filled up as people are developing an abstract layer on top of Map-Reduce and YARN frameworks which takes SQL and in turn convert it to Map-Reduce/Yarn.

Extract All Tar Files in a directory in Linux

This will first list the files containing extension tar.gz, and then awk will get the file names which is column 9 in

ls -lrth command, and

NF > 2 will remove the blank line and

tar -xvzf will extract files names contained in variable $i,

Like this we can experiment various operations like renaming all files with specific extension of so and can fiddled with to achieve various goals.


for i in `ls -lrth *.tar.gz |awk  'NF>2 {print $9}'`; do tar -xvzf $i; done

All about hadoop Balancer.

Hadoop Data Balancing

Hadoop Balancer:

This is tool provided to balance the disk uses throughout the Hadoop cluster. I may happen sometime that some of the nodes in the cluster becomes over utilized or underutilized, which occurs due to addition of new nodes where newly added nodes may be underutilized or if there are less number of nodes result in overutilization. We can run balancer from more than 1 machine in the cluster to increase the speed of balancing but it will increase bandwidth uses to very high.

This tool requires administrator right on the Hadoop cluster to run.

Syntax of the balancer:

bin/start-balancer.sh [-threshold <threshold>]

Where start-balancer.sh files resides in the bin directory of the Hadoop folder. And the threshold is the parameter which decides target of balance, this lies in fraction between 0,1 the default value is 10% if nothing is passed as the threshold value.

This process does the transferring of blocks between the nodes resulting network activity and if a production cluster must be used cautiously, as it result in some block missing error or late reply from the cluster.

This process can be stopped any time if required using following command: